LCOV - code coverage report
Current view: top level - kernel/time - timer.c (source / functions) Hit Total Coverage
Test: Real Lines: 353 392 90.1 %
Date: 2020-10-17 15:46:16 Functions: 6 56 10.7 %
Legend: Neither, QEMU, Real, Both Branches: 0 0 -

           Branch data     Line data    Source code
       1                 :            : // SPDX-License-Identifier: GPL-2.0
       2                 :            : /*
       3                 :            :  *  Kernel internal timers
       4                 :            :  *
       5                 :            :  *  Copyright (C) 1991, 1992  Linus Torvalds
       6                 :            :  *
       7                 :            :  *  1997-01-28  Modified by Finn Arne Gangstad to make timers scale better.
       8                 :            :  *
       9                 :            :  *  1997-09-10  Updated NTP code according to technical memorandum Jan '96
      10                 :            :  *              "A Kernel Model for Precision Timekeeping" by Dave Mills
      11                 :            :  *  1998-12-24  Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
      12                 :            :  *              serialize accesses to xtime/lost_ticks).
      13                 :            :  *                              Copyright (C) 1998  Andrea Arcangeli
      14                 :            :  *  1999-03-10  Improved NTP compatibility by Ulrich Windl
      15                 :            :  *  2002-05-31  Move sys_sysinfo here and make its locking sane, Robert Love
      16                 :            :  *  2000-10-05  Implemented scalable SMP per-CPU timer handling.
      17                 :            :  *                              Copyright (C) 2000, 2001, 2002  Ingo Molnar
      18                 :            :  *              Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
      19                 :            :  */
      20                 :            : 
      21                 :            : #include <linux/kernel_stat.h>
      22                 :            : #include <linux/export.h>
      23                 :            : #include <linux/interrupt.h>
      24                 :            : #include <linux/percpu.h>
      25                 :            : #include <linux/init.h>
      26                 :            : #include <linux/mm.h>
      27                 :            : #include <linux/swap.h>
      28                 :            : #include <linux/pid_namespace.h>
      29                 :            : #include <linux/notifier.h>
      30                 :            : #include <linux/thread_info.h>
      31                 :            : #include <linux/time.h>
      32                 :            : #include <linux/jiffies.h>
      33                 :            : #include <linux/posix-timers.h>
      34                 :            : #include <linux/cpu.h>
      35                 :            : #include <linux/syscalls.h>
      36                 :            : #include <linux/delay.h>
      37                 :            : #include <linux/tick.h>
      38                 :            : #include <linux/kallsyms.h>
      39                 :            : #include <linux/irq_work.h>
      40                 :            : #include <linux/sched/signal.h>
      41                 :            : #include <linux/sched/sysctl.h>
      42                 :            : #include <linux/sched/nohz.h>
      43                 :            : #include <linux/sched/debug.h>
      44                 :            : #include <linux/slab.h>
      45                 :            : #include <linux/compat.h>
      46                 :            : #include <linux/random.h>
      47                 :            : 
      48                 :            : #include <linux/uaccess.h>
      49                 :            : #include <asm/unistd.h>
      50                 :            : #include <asm/div64.h>
      51                 :            : #include <asm/timex.h>
      52                 :            : #include <asm/io.h>
      53                 :            : 
      54                 :            : #include "tick-internal.h"
      55                 :            : 
      56                 :            : #define CREATE_TRACE_POINTS
      57                 :            : #include <trace/events/timer.h>
      58                 :            : 
      59                 :            : __visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
      60                 :            : 
      61                 :            : EXPORT_SYMBOL(jiffies_64);
      62                 :            : 
      63                 :            : /*
      64                 :            :  * The timer wheel has LVL_DEPTH array levels. Each level provides an array of
      65                 :            :  * LVL_SIZE buckets. Each level is driven by its own clock and therefor each
      66                 :            :  * level has a different granularity.
      67                 :            :  *
      68                 :            :  * The level granularity is:            LVL_CLK_DIV ^ lvl
      69                 :            :  * The level clock frequency is:        HZ / (LVL_CLK_DIV ^ level)
      70                 :            :  *
      71                 :            :  * The array level of a newly armed timer depends on the relative expiry
      72                 :            :  * time. The farther the expiry time is away the higher the array level and
      73                 :            :  * therefor the granularity becomes.
      74                 :            :  *
      75                 :            :  * Contrary to the original timer wheel implementation, which aims for 'exact'
      76                 :            :  * expiry of the timers, this implementation removes the need for recascading
      77                 :            :  * the timers into the lower array levels. The previous 'classic' timer wheel
      78                 :            :  * implementation of the kernel already violated the 'exact' expiry by adding
      79                 :            :  * slack to the expiry time to provide batched expiration. The granularity
      80                 :            :  * levels provide implicit batching.
      81                 :            :  *
      82                 :            :  * This is an optimization of the original timer wheel implementation for the
      83                 :            :  * majority of the timer wheel use cases: timeouts. The vast majority of
      84                 :            :  * timeout timers (networking, disk I/O ...) are canceled before expiry. If
      85                 :            :  * the timeout expires it indicates that normal operation is disturbed, so it
      86                 :            :  * does not matter much whether the timeout comes with a slight delay.
      87                 :            :  *
      88                 :            :  * The only exception to this are networking timers with a small expiry
      89                 :            :  * time. They rely on the granularity. Those fit into the first wheel level,
      90                 :            :  * which has HZ granularity.
      91                 :            :  *
      92                 :            :  * We don't have cascading anymore. timers with a expiry time above the
      93                 :            :  * capacity of the last wheel level are force expired at the maximum timeout
      94                 :            :  * value of the last wheel level. From data sampling we know that the maximum
      95                 :            :  * value observed is 5 days (network connection tracking), so this should not
      96                 :            :  * be an issue.
      97                 :            :  *
      98                 :            :  * The currently chosen array constants values are a good compromise between
      99                 :            :  * array size and granularity.
     100                 :            :  *
     101                 :            :  * This results in the following granularity and range levels:
     102                 :            :  *
     103                 :            :  * HZ 1000 steps
     104                 :            :  * Level Offset  Granularity            Range
     105                 :            :  *  0      0         1 ms                0 ms -         63 ms
     106                 :            :  *  1     64         8 ms               64 ms -        511 ms
     107                 :            :  *  2    128        64 ms              512 ms -       4095 ms (512ms - ~4s)
     108                 :            :  *  3    192       512 ms             4096 ms -      32767 ms (~4s - ~32s)
     109                 :            :  *  4    256      4096 ms (~4s)      32768 ms -     262143 ms (~32s - ~4m)
     110                 :            :  *  5    320     32768 ms (~32s)    262144 ms -    2097151 ms (~4m - ~34m)
     111                 :            :  *  6    384    262144 ms (~4m)    2097152 ms -   16777215 ms (~34m - ~4h)
     112                 :            :  *  7    448   2097152 ms (~34m)  16777216 ms -  134217727 ms (~4h - ~1d)
     113                 :            :  *  8    512  16777216 ms (~4h)  134217728 ms - 1073741822 ms (~1d - ~12d)
     114                 :            :  *
     115                 :            :  * HZ  300
     116                 :            :  * Level Offset  Granularity            Range
     117                 :            :  *  0      0         3 ms                0 ms -        210 ms
     118                 :            :  *  1     64        26 ms              213 ms -       1703 ms (213ms - ~1s)
     119                 :            :  *  2    128       213 ms             1706 ms -      13650 ms (~1s - ~13s)
     120                 :            :  *  3    192      1706 ms (~1s)      13653 ms -     109223 ms (~13s - ~1m)
     121                 :            :  *  4    256     13653 ms (~13s)    109226 ms -     873810 ms (~1m - ~14m)
     122                 :            :  *  5    320    109226 ms (~1m)     873813 ms -    6990503 ms (~14m - ~1h)
     123                 :            :  *  6    384    873813 ms (~14m)   6990506 ms -   55924050 ms (~1h - ~15h)
     124                 :            :  *  7    448   6990506 ms (~1h)   55924053 ms -  447392423 ms (~15h - ~5d)
     125                 :            :  *  8    512  55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
     126                 :            :  *
     127                 :            :  * HZ  250
     128                 :            :  * Level Offset  Granularity            Range
     129                 :            :  *  0      0         4 ms                0 ms -        255 ms
     130                 :            :  *  1     64        32 ms              256 ms -       2047 ms (256ms - ~2s)
     131                 :            :  *  2    128       256 ms             2048 ms -      16383 ms (~2s - ~16s)
     132                 :            :  *  3    192      2048 ms (~2s)      16384 ms -     131071 ms (~16s - ~2m)
     133                 :            :  *  4    256     16384 ms (~16s)    131072 ms -    1048575 ms (~2m - ~17m)
     134                 :            :  *  5    320    131072 ms (~2m)    1048576 ms -    8388607 ms (~17m - ~2h)
     135                 :            :  *  6    384   1048576 ms (~17m)   8388608 ms -   67108863 ms (~2h - ~18h)
     136                 :            :  *  7    448   8388608 ms (~2h)   67108864 ms -  536870911 ms (~18h - ~6d)
     137                 :            :  *  8    512  67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
     138                 :            :  *
     139                 :            :  * HZ  100
     140                 :            :  * Level Offset  Granularity            Range
     141                 :            :  *  0      0         10 ms               0 ms -        630 ms
     142                 :            :  *  1     64         80 ms             640 ms -       5110 ms (640ms - ~5s)
     143                 :            :  *  2    128        640 ms            5120 ms -      40950 ms (~5s - ~40s)
     144                 :            :  *  3    192       5120 ms (~5s)     40960 ms -     327670 ms (~40s - ~5m)
     145                 :            :  *  4    256      40960 ms (~40s)   327680 ms -    2621430 ms (~5m - ~43m)
     146                 :            :  *  5    320     327680 ms (~5m)   2621440 ms -   20971510 ms (~43m - ~5h)
     147                 :            :  *  6    384    2621440 ms (~43m) 20971520 ms -  167772150 ms (~5h - ~1d)
     148                 :            :  *  7    448   20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
     149                 :            :  */
     150                 :            : 
     151                 :            : /* Clock divisor for the next level */
     152                 :            : #define LVL_CLK_SHIFT   3
     153                 :            : #define LVL_CLK_DIV     (1UL << LVL_CLK_SHIFT)
     154                 :            : #define LVL_CLK_MASK    (LVL_CLK_DIV - 1)
     155                 :            : #define LVL_SHIFT(n)    ((n) * LVL_CLK_SHIFT)
     156                 :            : #define LVL_GRAN(n)     (1UL << LVL_SHIFT(n))
     157                 :            : 
     158                 :            : /*
     159                 :            :  * The time start value for each level to select the bucket at enqueue
     160                 :            :  * time.
     161                 :            :  */
     162                 :            : #define LVL_START(n)    ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
     163                 :            : 
     164                 :            : /* Size of each clock level */
     165                 :            : #define LVL_BITS        6
     166                 :            : #define LVL_SIZE        (1UL << LVL_BITS)
     167                 :            : #define LVL_MASK        (LVL_SIZE - 1)
     168                 :            : #define LVL_OFFS(n)     ((n) * LVL_SIZE)
     169                 :            : 
     170                 :            : /* Level depth */
     171                 :            : #if HZ > 100
     172                 :            : # define LVL_DEPTH      9
     173                 :            : # else
     174                 :            : # define LVL_DEPTH      8
     175                 :            : #endif
     176                 :            : 
     177                 :            : /* The cutoff (max. capacity of the wheel) */
     178                 :            : #define WHEEL_TIMEOUT_CUTOFF    (LVL_START(LVL_DEPTH))
     179                 :            : #define WHEEL_TIMEOUT_MAX       (WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
     180                 :            : 
     181                 :            : /*
     182                 :            :  * The resulting wheel size. If NOHZ is configured we allocate two
     183                 :            :  * wheels so we have a separate storage for the deferrable timers.
     184                 :            :  */
     185                 :            : #define WHEEL_SIZE      (LVL_SIZE * LVL_DEPTH)
     186                 :            : 
     187                 :            : #ifdef CONFIG_NO_HZ_COMMON
     188                 :            : # define NR_BASES       2
     189                 :            : # define BASE_STD       0
     190                 :            : # define BASE_DEF       1
     191                 :            : #else
     192                 :            : # define NR_BASES       1
     193                 :            : # define BASE_STD       0
     194                 :            : # define BASE_DEF       0
     195                 :            : #endif
     196                 :            : 
     197                 :            : struct timer_base {
     198                 :            :         raw_spinlock_t          lock;
     199                 :            :         struct timer_list       *running_timer;
     200                 :            : #ifdef CONFIG_PREEMPT_RT
     201                 :            :         spinlock_t              expiry_lock;
     202                 :            :         atomic_t                timer_waiters;
     203                 :            : #endif
     204                 :            :         unsigned long           clk;
     205                 :            :         unsigned long           next_expiry;
     206                 :            :         unsigned int            cpu;
     207                 :            :         bool                    is_idle;
     208                 :            :         bool                    must_forward_clk;
     209                 :            :         DECLARE_BITMAP(pending_map, WHEEL_SIZE);
     210                 :            :         struct hlist_head       vectors[WHEEL_SIZE];
     211                 :            : } ____cacheline_aligned;
     212                 :            : 
     213                 :            : static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
     214                 :            : 
     215                 :            : #ifdef CONFIG_NO_HZ_COMMON
     216                 :            : 
     217                 :            : static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
     218                 :            : static DEFINE_MUTEX(timer_keys_mutex);
     219                 :            : 
     220                 :            : static void timer_update_keys(struct work_struct *work);
     221                 :            : static DECLARE_WORK(timer_update_work, timer_update_keys);
     222                 :            : 
     223                 :            : #ifdef CONFIG_SMP
     224                 :            : unsigned int sysctl_timer_migration = 1;
     225                 :            : 
     226                 :            : DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
     227                 :            : 
     228                 :          3 : static void timers_update_migration(void)
     229                 :            : {
     230                 :          3 :         if (sysctl_timer_migration && tick_nohz_active)
     231                 :          3 :                 static_branch_enable(&timers_migration_enabled);
     232                 :            :         else
     233                 :          0 :                 static_branch_disable(&timers_migration_enabled);
     234                 :          3 : }
     235                 :            : #else
     236                 :            : static inline void timers_update_migration(void) { }
     237                 :            : #endif /* !CONFIG_SMP */
     238                 :            : 
     239                 :          3 : static void timer_update_keys(struct work_struct *work)
     240                 :            : {
     241                 :          3 :         mutex_lock(&timer_keys_mutex);
     242                 :          3 :         timers_update_migration();
     243                 :          3 :         static_branch_enable(&timers_nohz_active);
     244                 :          3 :         mutex_unlock(&timer_keys_mutex);
     245                 :          3 : }
     246                 :            : 
     247                 :          3 : void timers_update_nohz(void)
     248                 :            : {
     249                 :            :         schedule_work(&timer_update_work);
     250                 :          3 : }
     251                 :            : 
     252                 :          0 : int timer_migration_handler(struct ctl_table *table, int write,
     253                 :            :                             void __user *buffer, size_t *lenp,
     254                 :            :                             loff_t *ppos)
     255                 :            : {
     256                 :            :         int ret;
     257                 :            : 
     258                 :          0 :         mutex_lock(&timer_keys_mutex);
     259                 :          0 :         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
     260                 :          0 :         if (!ret && write)
     261                 :          0 :                 timers_update_migration();
     262                 :          0 :         mutex_unlock(&timer_keys_mutex);
     263                 :          0 :         return ret;
     264                 :            : }
     265                 :            : 
     266                 :            : static inline bool is_timers_nohz_active(void)
     267                 :            : {
     268                 :          3 :         return static_branch_unlikely(&timers_nohz_active);
     269                 :            : }
     270                 :            : #else
     271                 :            : static inline bool is_timers_nohz_active(void) { return false; }
     272                 :            : #endif /* NO_HZ_COMMON */
     273                 :            : 
     274                 :            : static unsigned long round_jiffies_common(unsigned long j, int cpu,
     275                 :            :                 bool force_up)
     276                 :            : {
     277                 :            :         int rem;
     278                 :            :         unsigned long original = j;
     279                 :            : 
     280                 :            :         /*
     281                 :            :          * We don't want all cpus firing their timers at once hitting the
     282                 :            :          * same lock or cachelines, so we skew each extra cpu with an extra
     283                 :            :          * 3 jiffies. This 3 jiffies came originally from the mm/ code which
     284                 :            :          * already did this.
     285                 :            :          * The skew is done by adding 3*cpunr, then round, then subtract this
     286                 :            :          * extra offset again.
     287                 :            :          */
     288                 :          3 :         j += cpu * 3;
     289                 :            : 
     290                 :          3 :         rem = j % HZ;
     291                 :            : 
     292                 :            :         /*
     293                 :            :          * If the target jiffie is just after a whole second (which can happen
     294                 :            :          * due to delays of the timer irq, long irq off times etc etc) then
     295                 :            :          * we should round down to the whole second, not up. Use 1/4th second
     296                 :            :          * as cutoff for this rounding as an extreme upper bound for this.
     297                 :            :          * But never round down if @force_up is set.
     298                 :            :          */
     299                 :          3 :         if (rem < HZ/4 && !force_up) /* round down */
     300                 :          3 :                 j = j - rem;
     301                 :            :         else /* round up */
     302                 :          3 :                 j = j - rem + HZ;
     303                 :            : 
     304                 :            :         /* now that we have rounded, subtract the extra skew again */
     305                 :          3 :         j -= cpu * 3;
     306                 :            : 
     307                 :            :         /*
     308                 :            :          * Make sure j is still in the future. Otherwise return the
     309                 :            :          * unmodified value.
     310                 :            :          */
     311                 :          3 :         return time_is_after_jiffies(j) ? j : original;
     312                 :            : }
     313                 :            : 
     314                 :            : /**
     315                 :            :  * __round_jiffies - function to round jiffies to a full second
     316                 :            :  * @j: the time in (absolute) jiffies that should be rounded
     317                 :            :  * @cpu: the processor number on which the timeout will happen
     318                 :            :  *
     319                 :            :  * __round_jiffies() rounds an absolute time in the future (in jiffies)
     320                 :            :  * up or down to (approximately) full seconds. This is useful for timers
     321                 :            :  * for which the exact time they fire does not matter too much, as long as
     322                 :            :  * they fire approximately every X seconds.
     323                 :            :  *
     324                 :            :  * By rounding these timers to whole seconds, all such timers will fire
     325                 :            :  * at the same time, rather than at various times spread out. The goal
     326                 :            :  * of this is to have the CPU wake up less, which saves power.
     327                 :            :  *
     328                 :            :  * The exact rounding is skewed for each processor to avoid all
     329                 :            :  * processors firing at the exact same time, which could lead
     330                 :            :  * to lock contention or spurious cache line bouncing.
     331                 :            :  *
     332                 :            :  * The return value is the rounded version of the @j parameter.
     333                 :            :  */
     334                 :          0 : unsigned long __round_jiffies(unsigned long j, int cpu)
     335                 :            : {
     336                 :          0 :         return round_jiffies_common(j, cpu, false);
     337                 :            : }
     338                 :            : EXPORT_SYMBOL_GPL(__round_jiffies);
     339                 :            : 
     340                 :            : /**
     341                 :            :  * __round_jiffies_relative - function to round jiffies to a full second
     342                 :            :  * @j: the time in (relative) jiffies that should be rounded
     343                 :            :  * @cpu: the processor number on which the timeout will happen
     344                 :            :  *
     345                 :            :  * __round_jiffies_relative() rounds a time delta  in the future (in jiffies)
     346                 :            :  * up or down to (approximately) full seconds. This is useful for timers
     347                 :            :  * for which the exact time they fire does not matter too much, as long as
     348                 :            :  * they fire approximately every X seconds.
     349                 :            :  *
     350                 :            :  * By rounding these timers to whole seconds, all such timers will fire
     351                 :            :  * at the same time, rather than at various times spread out. The goal
     352                 :            :  * of this is to have the CPU wake up less, which saves power.
     353                 :            :  *
     354                 :            :  * The exact rounding is skewed for each processor to avoid all
     355                 :            :  * processors firing at the exact same time, which could lead
     356                 :            :  * to lock contention or spurious cache line bouncing.
     357                 :            :  *
     358                 :            :  * The return value is the rounded version of the @j parameter.
     359                 :            :  */
     360                 :          3 : unsigned long __round_jiffies_relative(unsigned long j, int cpu)
     361                 :            : {
     362                 :          3 :         unsigned long j0 = jiffies;
     363                 :            : 
     364                 :            :         /* Use j0 because jiffies might change while we run */
     365                 :          3 :         return round_jiffies_common(j + j0, cpu, false) - j0;
     366                 :            : }
     367                 :            : EXPORT_SYMBOL_GPL(__round_jiffies_relative);
     368                 :            : 
     369                 :            : /**
     370                 :            :  * round_jiffies - function to round jiffies to a full second
     371                 :            :  * @j: the time in (absolute) jiffies that should be rounded
     372                 :            :  *
     373                 :            :  * round_jiffies() rounds an absolute time in the future (in jiffies)
     374                 :            :  * up or down to (approximately) full seconds. This is useful for timers
     375                 :            :  * for which the exact time they fire does not matter too much, as long as
     376                 :            :  * they fire approximately every X seconds.
     377                 :            :  *
     378                 :            :  * By rounding these timers to whole seconds, all such timers will fire
     379                 :            :  * at the same time, rather than at various times spread out. The goal
     380                 :            :  * of this is to have the CPU wake up less, which saves power.
     381                 :            :  *
     382                 :            :  * The return value is the rounded version of the @j parameter.
     383                 :            :  */
     384                 :          3 : unsigned long round_jiffies(unsigned long j)
     385                 :            : {
     386                 :          3 :         return round_jiffies_common(j, raw_smp_processor_id(), false);
     387                 :            : }
     388                 :            : EXPORT_SYMBOL_GPL(round_jiffies);
     389                 :            : 
     390                 :            : /**
     391                 :            :  * round_jiffies_relative - function to round jiffies to a full second
     392                 :            :  * @j: the time in (relative) jiffies that should be rounded
     393                 :            :  *
     394                 :            :  * round_jiffies_relative() rounds a time delta  in the future (in jiffies)
     395                 :            :  * up or down to (approximately) full seconds. This is useful for timers
     396                 :            :  * for which the exact time they fire does not matter too much, as long as
     397                 :            :  * they fire approximately every X seconds.
     398                 :            :  *
     399                 :            :  * By rounding these timers to whole seconds, all such timers will fire
     400                 :            :  * at the same time, rather than at various times spread out. The goal
     401                 :            :  * of this is to have the CPU wake up less, which saves power.
     402                 :            :  *
     403                 :            :  * The return value is the rounded version of the @j parameter.
     404                 :            :  */
     405                 :          3 : unsigned long round_jiffies_relative(unsigned long j)
     406                 :            : {
     407                 :          3 :         return __round_jiffies_relative(j, raw_smp_processor_id());
     408                 :            : }
     409                 :            : EXPORT_SYMBOL_GPL(round_jiffies_relative);
     410                 :            : 
     411                 :            : /**
     412                 :            :  * __round_jiffies_up - function to round jiffies up to a full second
     413                 :            :  * @j: the time in (absolute) jiffies that should be rounded
     414                 :            :  * @cpu: the processor number on which the timeout will happen
     415                 :            :  *
     416                 :            :  * This is the same as __round_jiffies() except that it will never
     417                 :            :  * round down.  This is useful for timeouts for which the exact time
     418                 :            :  * of firing does not matter too much, as long as they don't fire too
     419                 :            :  * early.
     420                 :            :  */
     421                 :          0 : unsigned long __round_jiffies_up(unsigned long j, int cpu)
     422                 :            : {
     423                 :          0 :         return round_jiffies_common(j, cpu, true);
     424                 :            : }
     425                 :            : EXPORT_SYMBOL_GPL(__round_jiffies_up);
     426                 :            : 
     427                 :            : /**
     428                 :            :  * __round_jiffies_up_relative - function to round jiffies up to a full second
     429                 :            :  * @j: the time in (relative) jiffies that should be rounded
     430                 :            :  * @cpu: the processor number on which the timeout will happen
     431                 :            :  *
     432                 :            :  * This is the same as __round_jiffies_relative() except that it will never
     433                 :            :  * round down.  This is useful for timeouts for which the exact time
     434                 :            :  * of firing does not matter too much, as long as they don't fire too
     435                 :            :  * early.
     436                 :            :  */
     437                 :          0 : unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
     438                 :            : {
     439                 :          0 :         unsigned long j0 = jiffies;
     440                 :            : 
     441                 :            :         /* Use j0 because jiffies might change while we run */
     442                 :          0 :         return round_jiffies_common(j + j0, cpu, true) - j0;
     443                 :            : }
     444                 :            : EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
     445                 :            : 
     446                 :            : /**
     447                 :            :  * round_jiffies_up - function to round jiffies up to a full second
     448                 :            :  * @j: the time in (absolute) jiffies that should be rounded
     449                 :            :  *
     450                 :            :  * This is the same as round_jiffies() except that it will never
     451                 :            :  * round down.  This is useful for timeouts for which the exact time
     452                 :            :  * of firing does not matter too much, as long as they don't fire too
     453                 :            :  * early.
     454                 :            :  */
     455                 :          3 : unsigned long round_jiffies_up(unsigned long j)
     456                 :            : {
     457                 :          3 :         return round_jiffies_common(j, raw_smp_processor_id(), true);
     458                 :            : }
     459                 :            : EXPORT_SYMBOL_GPL(round_jiffies_up);
     460                 :            : 
     461                 :            : /**
     462                 :            :  * round_jiffies_up_relative - function to round jiffies up to a full second
     463                 :            :  * @j: the time in (relative) jiffies that should be rounded
     464                 :            :  *
     465                 :            :  * This is the same as round_jiffies_relative() except that it will never
     466                 :            :  * round down.  This is useful for timeouts for which the exact time
     467                 :            :  * of firing does not matter too much, as long as they don't fire too
     468                 :            :  * early.
     469                 :            :  */
     470                 :          0 : unsigned long round_jiffies_up_relative(unsigned long j)
     471                 :            : {
     472                 :          0 :         return __round_jiffies_up_relative(j, raw_smp_processor_id());
     473                 :            : }
     474                 :            : EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
     475                 :            : 
     476                 :            : 
     477                 :            : static inline unsigned int timer_get_idx(struct timer_list *timer)
     478                 :            : {
     479                 :          3 :         return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
     480                 :            : }
     481                 :            : 
     482                 :            : static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
     483                 :            : {
     484                 :          3 :         timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
     485                 :          3 :                         idx << TIMER_ARRAYSHIFT;
     486                 :            : }
     487                 :            : 
     488                 :            : /*
     489                 :            :  * Helper function to calculate the array index for a given expiry
     490                 :            :  * time.
     491                 :            :  */
     492                 :            : static inline unsigned calc_index(unsigned expires, unsigned lvl)
     493                 :            : {
     494                 :          3 :         expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
     495                 :          3 :         return LVL_OFFS(lvl) + (expires & LVL_MASK);
     496                 :            : }
     497                 :            : 
     498                 :          3 : static int calc_wheel_index(unsigned long expires, unsigned long clk)
     499                 :            : {
     500                 :          3 :         unsigned long delta = expires - clk;
     501                 :            :         unsigned int idx;
     502                 :            : 
     503                 :          3 :         if (delta < LVL_START(1)) {
     504                 :            :                 idx = calc_index(expires, 0);
     505                 :          3 :         } else if (delta < LVL_START(2)) {
     506                 :            :                 idx = calc_index(expires, 1);
     507                 :          3 :         } else if (delta < LVL_START(3)) {
     508                 :            :                 idx = calc_index(expires, 2);
     509                 :          3 :         } else if (delta < LVL_START(4)) {
     510                 :            :                 idx = calc_index(expires, 3);
     511                 :          3 :         } else if (delta < LVL_START(5)) {
     512                 :            :                 idx = calc_index(expires, 4);
     513                 :          3 :         } else if (delta < LVL_START(6)) {
     514                 :            :                 idx = calc_index(expires, 5);
     515                 :          3 :         } else if (delta < LVL_START(7)) {
     516                 :            :                 idx = calc_index(expires, 6);
     517                 :            :         } else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
     518                 :            :                 idx = calc_index(expires, 7);
     519                 :          3 :         } else if ((long) delta < 0) {
     520                 :          3 :                 idx = clk & LVL_MASK;
     521                 :            :         } else {
     522                 :            :                 /*
     523                 :            :                  * Force expire obscene large timeouts to expire at the
     524                 :            :                  * capacity limit of the wheel.
     525                 :            :                  */
     526                 :          0 :                 if (delta >= WHEEL_TIMEOUT_CUTOFF)
     527                 :          0 :                         expires = clk + WHEEL_TIMEOUT_MAX;
     528                 :            : 
     529                 :            :                 idx = calc_index(expires, LVL_DEPTH - 1);
     530                 :            :         }
     531                 :          3 :         return idx;
     532                 :            : }
     533                 :            : 
     534                 :            : /*
     535                 :            :  * Enqueue the timer into the hash bucket, mark it pending in
     536                 :            :  * the bitmap and store the index in the timer flags.
     537                 :            :  */
     538                 :          3 : static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
     539                 :            :                           unsigned int idx)
     540                 :            : {
     541                 :          3 :         hlist_add_head(&timer->entry, base->vectors + idx);
     542                 :          3 :         __set_bit(idx, base->pending_map);
     543                 :            :         timer_set_idx(timer, idx);
     544                 :            : 
     545                 :          3 :         trace_timer_start(timer, timer->expires, timer->flags);
     546                 :          3 : }
     547                 :            : 
     548                 :            : static void
     549                 :          3 : __internal_add_timer(struct timer_base *base, struct timer_list *timer)
     550                 :            : {
     551                 :            :         unsigned int idx;
     552                 :            : 
     553                 :          3 :         idx = calc_wheel_index(timer->expires, base->clk);
     554                 :          3 :         enqueue_timer(base, timer, idx);
     555                 :          3 : }
     556                 :            : 
     557                 :            : static void
     558                 :          3 : trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
     559                 :            : {
     560                 :          3 :         if (!is_timers_nohz_active())
     561                 :            :                 return;
     562                 :            : 
     563                 :            :         /*
     564                 :            :          * TODO: This wants some optimizing similar to the code below, but we
     565                 :            :          * will do that when we switch from push to pull for deferrable timers.
     566                 :            :          */
     567                 :          3 :         if (timer->flags & TIMER_DEFERRABLE) {
     568                 :            :                 if (tick_nohz_full_cpu(base->cpu))
     569                 :            :                         wake_up_nohz_cpu(base->cpu);
     570                 :            :                 return;
     571                 :            :         }
     572                 :            : 
     573                 :            :         /*
     574                 :            :          * We might have to IPI the remote CPU if the base is idle and the
     575                 :            :          * timer is not deferrable. If the other CPU is on the way to idle
     576                 :            :          * then it can't set base->is_idle as we hold the base lock:
     577                 :            :          */
     578                 :          3 :         if (!base->is_idle)
     579                 :            :                 return;
     580                 :            : 
     581                 :            :         /* Check whether this is the new first expiring timer: */
     582                 :          3 :         if (time_after_eq(timer->expires, base->next_expiry))
     583                 :            :                 return;
     584                 :            : 
     585                 :            :         /*
     586                 :            :          * Set the next expiry time and kick the CPU so it can reevaluate the
     587                 :            :          * wheel:
     588                 :            :          */
     589                 :          3 :         if (time_before(timer->expires, base->clk)) {
     590                 :            :                 /*
     591                 :            :                  * Prevent from forward_timer_base() moving the base->clk
     592                 :            :                  * backward
     593                 :            :                  */
     594                 :          0 :                 base->next_expiry = base->clk;
     595                 :            :         } else {
     596                 :          3 :                 base->next_expiry = timer->expires;
     597                 :            :         }
     598                 :          3 :         wake_up_nohz_cpu(base->cpu);
     599                 :            : }
     600                 :            : 
     601                 :            : static void
     602                 :            : internal_add_timer(struct timer_base *base, struct timer_list *timer)
     603                 :            : {
     604                 :          3 :         __internal_add_timer(base, timer);
     605                 :          3 :         trigger_dyntick_cpu(base, timer);
     606                 :            : }
     607                 :            : 
     608                 :            : #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
     609                 :            : 
     610                 :            : static struct debug_obj_descr timer_debug_descr;
     611                 :            : 
     612                 :            : static void *timer_debug_hint(void *addr)
     613                 :            : {
     614                 :            :         return ((struct timer_list *) addr)->function;
     615                 :            : }
     616                 :            : 
     617                 :            : static bool timer_is_static_object(void *addr)
     618                 :            : {
     619                 :            :         struct timer_list *timer = addr;
     620                 :            : 
     621                 :            :         return (timer->entry.pprev == NULL &&
     622                 :            :                 timer->entry.next == TIMER_ENTRY_STATIC);
     623                 :            : }
     624                 :            : 
     625                 :            : /*
     626                 :            :  * fixup_init is called when:
     627                 :            :  * - an active object is initialized
     628                 :            :  */
     629                 :            : static bool timer_fixup_init(void *addr, enum debug_obj_state state)
     630                 :            : {
     631                 :            :         struct timer_list *timer = addr;
     632                 :            : 
     633                 :            :         switch (state) {
     634                 :            :         case ODEBUG_STATE_ACTIVE:
     635                 :            :                 del_timer_sync(timer);
     636                 :            :                 debug_object_init(timer, &timer_debug_descr);
     637                 :            :                 return true;
     638                 :            :         default:
     639                 :            :                 return false;
     640                 :            :         }
     641                 :            : }
     642                 :            : 
     643                 :            : /* Stub timer callback for improperly used timers. */
     644                 :            : static void stub_timer(struct timer_list *unused)
     645                 :            : {
     646                 :            :         WARN_ON(1);
     647                 :            : }
     648                 :            : 
     649                 :            : /*
     650                 :            :  * fixup_activate is called when:
     651                 :            :  * - an active object is activated
     652                 :            :  * - an unknown non-static object is activated
     653                 :            :  */
     654                 :            : static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
     655                 :            : {
     656                 :            :         struct timer_list *timer = addr;
     657                 :            : 
     658                 :            :         switch (state) {
     659                 :            :         case ODEBUG_STATE_NOTAVAILABLE:
     660                 :            :                 timer_setup(timer, stub_timer, 0);
     661                 :            :                 return true;
     662                 :            : 
     663                 :            :         case ODEBUG_STATE_ACTIVE:
     664                 :            :                 WARN_ON(1);
     665                 :            :                 /* fall through */
     666                 :            :         default:
     667                 :            :                 return false;
     668                 :            :         }
     669                 :            : }
     670                 :            : 
     671                 :            : /*
     672                 :            :  * fixup_free is called when:
     673                 :            :  * - an active object is freed
     674                 :            :  */
     675                 :            : static bool timer_fixup_free(void *addr, enum debug_obj_state state)
     676                 :            : {
     677                 :            :         struct timer_list *timer = addr;
     678                 :            : 
     679                 :            :         switch (state) {
     680                 :            :         case ODEBUG_STATE_ACTIVE:
     681                 :            :                 del_timer_sync(timer);
     682                 :            :                 debug_object_free(timer, &timer_debug_descr);
     683                 :            :                 return true;
     684                 :            :         default:
     685                 :            :                 return false;
     686                 :            :         }
     687                 :            : }
     688                 :            : 
     689                 :            : /*
     690                 :            :  * fixup_assert_init is called when:
     691                 :            :  * - an untracked/uninit-ed object is found
     692                 :            :  */
     693                 :            : static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
     694                 :            : {
     695                 :            :         struct timer_list *timer = addr;
     696                 :            : 
     697                 :            :         switch (state) {
     698                 :            :         case ODEBUG_STATE_NOTAVAILABLE:
     699                 :            :                 timer_setup(timer, stub_timer, 0);
     700                 :            :                 return true;
     701                 :            :         default:
     702                 :            :                 return false;
     703                 :            :         }
     704                 :            : }
     705                 :            : 
     706                 :            : static struct debug_obj_descr timer_debug_descr = {
     707                 :            :         .name                   = "timer_list",
     708                 :            :         .debug_hint             = timer_debug_hint,
     709                 :            :         .is_static_object       = timer_is_static_object,
     710                 :            :         .fixup_init             = timer_fixup_init,
     711                 :            :         .fixup_activate         = timer_fixup_activate,
     712                 :            :         .fixup_free             = timer_fixup_free,
     713                 :            :         .fixup_assert_init      = timer_fixup_assert_init,
     714                 :            : };
     715                 :            : 
     716                 :            : static inline void debug_timer_init(struct timer_list *timer)
     717                 :            : {
     718                 :            :         debug_object_init(timer, &timer_debug_descr);
     719                 :            : }
     720                 :            : 
     721                 :            : static inline void debug_timer_activate(struct timer_list *timer)
     722                 :            : {
     723                 :            :         debug_object_activate(timer, &timer_debug_descr);
     724                 :            : }
     725                 :            : 
     726                 :            : static inline void debug_timer_deactivate(struct timer_list *timer)
     727                 :            : {
     728                 :            :         debug_object_deactivate(timer, &timer_debug_descr);
     729                 :            : }
     730                 :            : 
     731                 :            : static inline void debug_timer_free(struct timer_list *timer)
     732                 :            : {
     733                 :            :         debug_object_free(timer, &timer_debug_descr);
     734                 :            : }
     735                 :            : 
     736                 :            : static inline void debug_timer_assert_init(struct timer_list *timer)
     737                 :            : {
     738                 :            :         debug_object_assert_init(timer, &timer_debug_descr);
     739                 :            : }
     740                 :            : 
     741                 :            : static void do_init_timer(struct timer_list *timer,
     742                 :            :                           void (*func)(struct timer_list *),
     743                 :            :                           unsigned int flags,
     744                 :            :                           const char *name, struct lock_class_key *key);
     745                 :            : 
     746                 :            : void init_timer_on_stack_key(struct timer_list *timer,
     747                 :            :                              void (*func)(struct timer_list *),
     748                 :            :                              unsigned int flags,
     749                 :            :                              const char *name, struct lock_class_key *key)
     750                 :            : {
     751                 :            :         debug_object_init_on_stack(timer, &timer_debug_descr);
     752                 :            :         do_init_timer(timer, func, flags, name, key);
     753                 :            : }
     754                 :            : EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
     755                 :            : 
     756                 :            : void destroy_timer_on_stack(struct timer_list *timer)
     757                 :            : {
     758                 :            :         debug_object_free(timer, &timer_debug_descr);
     759                 :            : }
     760                 :            : EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
     761                 :            : 
     762                 :            : #else
     763                 :            : static inline void debug_timer_init(struct timer_list *timer) { }
     764                 :            : static inline void debug_timer_activate(struct timer_list *timer) { }
     765                 :            : static inline void debug_timer_deactivate(struct timer_list *timer) { }
     766                 :            : static inline void debug_timer_assert_init(struct timer_list *timer) { }
     767                 :            : #endif
     768                 :            : 
     769                 :            : static inline void debug_init(struct timer_list *timer)
     770                 :            : {
     771                 :            :         debug_timer_init(timer);
     772                 :          3 :         trace_timer_init(timer);
     773                 :            : }
     774                 :            : 
     775                 :            : static inline void debug_deactivate(struct timer_list *timer)
     776                 :            : {
     777                 :            :         debug_timer_deactivate(timer);
     778                 :          3 :         trace_timer_cancel(timer);
     779                 :            : }
     780                 :            : 
     781                 :            : static inline void debug_assert_init(struct timer_list *timer)
     782                 :            : {
     783                 :            :         debug_timer_assert_init(timer);
     784                 :            : }
     785                 :            : 
     786                 :            : static void do_init_timer(struct timer_list *timer,
     787                 :            :                           void (*func)(struct timer_list *),
     788                 :            :                           unsigned int flags,
     789                 :            :                           const char *name, struct lock_class_key *key)
     790                 :            : {
     791                 :          3 :         timer->entry.pprev = NULL;
     792                 :          3 :         timer->function = func;
     793                 :          3 :         timer->flags = flags | raw_smp_processor_id();
     794                 :            :         lockdep_init_map(&timer->lockdep_map, name, key, 0);
     795                 :            : }
     796                 :            : 
     797                 :            : /**
     798                 :            :  * init_timer_key - initialize a timer
     799                 :            :  * @timer: the timer to be initialized
     800                 :            :  * @func: timer callback function
     801                 :            :  * @flags: timer flags
     802                 :            :  * @name: name of the timer
     803                 :            :  * @key: lockdep class key of the fake lock used for tracking timer
     804                 :            :  *       sync lock dependencies
     805                 :            :  *
     806                 :            :  * init_timer_key() must be done to a timer prior calling *any* of the
     807                 :            :  * other timer functions.
     808                 :            :  */
     809                 :          3 : void init_timer_key(struct timer_list *timer,
     810                 :            :                     void (*func)(struct timer_list *), unsigned int flags,
     811                 :            :                     const char *name, struct lock_class_key *key)
     812                 :            : {
     813                 :            :         debug_init(timer);
     814                 :            :         do_init_timer(timer, func, flags, name, key);
     815                 :          3 : }
     816                 :            : EXPORT_SYMBOL(init_timer_key);
     817                 :            : 
     818                 :          3 : static inline void detach_timer(struct timer_list *timer, bool clear_pending)
     819                 :            : {
     820                 :            :         struct hlist_node *entry = &timer->entry;
     821                 :            : 
     822                 :            :         debug_deactivate(timer);
     823                 :            : 
     824                 :            :         __hlist_del(entry);
     825                 :          3 :         if (clear_pending)
     826                 :          3 :                 entry->pprev = NULL;
     827                 :          3 :         entry->next = LIST_POISON2;
     828                 :          3 : }
     829                 :            : 
     830                 :          3 : static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
     831                 :            :                              bool clear_pending)
     832                 :            : {
     833                 :            :         unsigned idx = timer_get_idx(timer);
     834                 :            : 
     835                 :          3 :         if (!timer_pending(timer))
     836                 :            :                 return 0;
     837                 :            : 
     838                 :          3 :         if (hlist_is_singular_node(&timer->entry, base->vectors + idx))
     839                 :          3 :                 __clear_bit(idx, base->pending_map);
     840                 :            : 
     841                 :          3 :         detach_timer(timer, clear_pending);
     842                 :          3 :         return 1;
     843                 :            : }
     844                 :            : 
     845                 :            : static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
     846                 :            : {
     847                 :          3 :         struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
     848                 :            : 
     849                 :            :         /*
     850                 :            :          * If the timer is deferrable and NO_HZ_COMMON is set then we need
     851                 :            :          * to use the deferrable base.
     852                 :            :          */
     853                 :          3 :         if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
     854                 :          3 :                 base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
     855                 :            :         return base;
     856                 :            : }
     857                 :            : 
     858                 :            : static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
     859                 :            : {
     860                 :          3 :         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
     861                 :            : 
     862                 :            :         /*
     863                 :            :          * If the timer is deferrable and NO_HZ_COMMON is set then we need
     864                 :            :          * to use the deferrable base.
     865                 :            :          */
     866                 :          3 :         if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
     867                 :          3 :                 base = this_cpu_ptr(&timer_bases[BASE_DEF]);
     868                 :            :         return base;
     869                 :            : }
     870                 :            : 
     871                 :            : static inline struct timer_base *get_timer_base(u32 tflags)
     872                 :            : {
     873                 :          3 :         return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
     874                 :            : }
     875                 :            : 
     876                 :            : static inline struct timer_base *
     877                 :          3 : get_target_base(struct timer_base *base, unsigned tflags)
     878                 :            : {
     879                 :            : #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
     880                 :          3 :         if (static_branch_likely(&timers_migration_enabled) &&
     881                 :          3 :             !(tflags & TIMER_PINNED))
     882                 :          3 :                 return get_timer_cpu_base(tflags, get_nohz_timer_target());
     883                 :            : #endif
     884                 :          3 :         return get_timer_this_cpu_base(tflags);
     885                 :            : }
     886                 :            : 
     887                 :          3 : static inline void forward_timer_base(struct timer_base *base)
     888                 :            : {
     889                 :            : #ifdef CONFIG_NO_HZ_COMMON
     890                 :            :         unsigned long jnow;
     891                 :            : 
     892                 :            :         /*
     893                 :            :          * We only forward the base when we are idle or have just come out of
     894                 :            :          * idle (must_forward_clk logic), and have a delta between base clock
     895                 :            :          * and jiffies. In the common case, run_timers will take care of it.
     896                 :            :          */
     897                 :          3 :         if (likely(!base->must_forward_clk))
     898                 :            :                 return;
     899                 :            : 
     900                 :          3 :         jnow = READ_ONCE(jiffies);
     901                 :          3 :         base->must_forward_clk = base->is_idle;
     902                 :          3 :         if ((long)(jnow - base->clk) < 2)
     903                 :            :                 return;
     904                 :            : 
     905                 :            :         /*
     906                 :            :          * If the next expiry value is > jiffies, then we fast forward to
     907                 :            :          * jiffies otherwise we forward to the next expiry value.
     908                 :            :          */
     909                 :          3 :         if (time_after(base->next_expiry, jnow)) {
     910                 :          3 :                 base->clk = jnow;
     911                 :            :         } else {
     912                 :          1 :                 if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk)))
     913                 :            :                         return;
     914                 :          1 :                 base->clk = base->next_expiry;
     915                 :            :         }
     916                 :            : #endif
     917                 :            : }
     918                 :            : 
     919                 :            : 
     920                 :            : /*
     921                 :            :  * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
     922                 :            :  * that all timers which are tied to this base are locked, and the base itself
     923                 :            :  * is locked too.
     924                 :            :  *
     925                 :            :  * So __run_timers/migrate_timers can safely modify all timers which could
     926                 :            :  * be found in the base->vectors array.
     927                 :            :  *
     928                 :            :  * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
     929                 :            :  * to wait until the migration is done.
     930                 :            :  */
     931                 :          3 : static struct timer_base *lock_timer_base(struct timer_list *timer,
     932                 :            :                                           unsigned long *flags)
     933                 :            :         __acquires(timer->base->lock)
     934                 :            : {
     935                 :            :         for (;;) {
     936                 :            :                 struct timer_base *base;
     937                 :            :                 u32 tf;
     938                 :            : 
     939                 :            :                 /*
     940                 :            :                  * We need to use READ_ONCE() here, otherwise the compiler
     941                 :            :                  * might re-read @tf between the check for TIMER_MIGRATING
     942                 :            :                  * and spin_lock().
     943                 :            :                  */
     944                 :            :                 tf = READ_ONCE(timer->flags);
     945                 :            : 
     946                 :          3 :                 if (!(tf & TIMER_MIGRATING)) {
     947                 :            :                         base = get_timer_base(tf);
     948                 :          3 :                         raw_spin_lock_irqsave(&base->lock, *flags);
     949                 :          3 :                         if (timer->flags == tf)
     950                 :          3 :                                 return base;
     951                 :          3 :                         raw_spin_unlock_irqrestore(&base->lock, *flags);
     952                 :            :                 }
     953                 :          3 :                 cpu_relax();
     954                 :          3 :         }
     955                 :            : }
     956                 :            : 
     957                 :            : #define MOD_TIMER_PENDING_ONLY          0x01
     958                 :            : #define MOD_TIMER_REDUCE                0x02
     959                 :            : 
     960                 :            : static inline int
     961                 :          3 : __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
     962                 :            : {
     963                 :            :         struct timer_base *base, *new_base;
     964                 :            :         unsigned int idx = UINT_MAX;
     965                 :            :         unsigned long clk = 0, flags;
     966                 :            :         int ret = 0;
     967                 :            : 
     968                 :          3 :         BUG_ON(!timer->function);
     969                 :            : 
     970                 :            :         /*
     971                 :            :          * This is a common optimization triggered by the networking code - if
     972                 :            :          * the timer is re-modified to have the same timeout or ends up in the
     973                 :            :          * same array bucket then just return:
     974                 :            :          */
     975                 :          3 :         if (timer_pending(timer)) {
     976                 :            :                 /*
     977                 :            :                  * The downside of this optimization is that it can result in
     978                 :            :                  * larger granularity than you would get from adding a new
     979                 :            :                  * timer with this expiry.
     980                 :            :                  */
     981                 :          3 :                 long diff = timer->expires - expires;
     982                 :            : 
     983                 :          3 :                 if (!diff)
     984                 :            :                         return 1;
     985                 :          3 :                 if (options & MOD_TIMER_REDUCE && diff <= 0)
     986                 :            :                         return 1;
     987                 :            : 
     988                 :            :                 /*
     989                 :            :                  * We lock timer base and calculate the bucket index right
     990                 :            :                  * here. If the timer ends up in the same bucket, then we
     991                 :            :                  * just update the expiry time and avoid the whole
     992                 :            :                  * dequeue/enqueue dance.
     993                 :            :                  */
     994                 :          3 :                 base = lock_timer_base(timer, &flags);
     995                 :          3 :                 forward_timer_base(base);
     996                 :            : 
     997                 :          3 :                 if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
     998                 :          0 :                     time_before_eq(timer->expires, expires)) {
     999                 :            :                         ret = 1;
    1000                 :            :                         goto out_unlock;
    1001                 :            :                 }
    1002                 :            : 
    1003                 :          3 :                 clk = base->clk;
    1004                 :          3 :                 idx = calc_wheel_index(expires, clk);
    1005                 :            : 
    1006                 :            :                 /*
    1007                 :            :                  * Retrieve and compare the array index of the pending
    1008                 :            :                  * timer. If it matches set the expiry to the new value so a
    1009                 :            :                  * subsequent call will exit in the expires check above.
    1010                 :            :                  */
    1011                 :          3 :                 if (idx == timer_get_idx(timer)) {
    1012                 :          3 :                         if (!(options & MOD_TIMER_REDUCE))
    1013                 :          3 :                                 timer->expires = expires;
    1014                 :          0 :                         else if (time_after(timer->expires, expires))
    1015                 :          0 :                                 timer->expires = expires;
    1016                 :            :                         ret = 1;
    1017                 :            :                         goto out_unlock;
    1018                 :            :                 }
    1019                 :            :         } else {
    1020                 :          3 :                 base = lock_timer_base(timer, &flags);
    1021                 :          3 :                 forward_timer_base(base);
    1022                 :            :         }
    1023                 :            : 
    1024                 :          3 :         ret = detach_if_pending(timer, base, false);
    1025                 :          3 :         if (!ret && (options & MOD_TIMER_PENDING_ONLY))
    1026                 :            :                 goto out_unlock;
    1027                 :            : 
    1028                 :          3 :         new_base = get_target_base(base, timer->flags);
    1029                 :            : 
    1030                 :          3 :         if (base != new_base) {
    1031                 :            :                 /*
    1032                 :            :                  * We are trying to schedule the timer on the new base.
    1033                 :            :                  * However we can't change timer's base while it is running,
    1034                 :            :                  * otherwise del_timer_sync() can't detect that the timer's
    1035                 :            :                  * handler yet has not finished. This also guarantees that the
    1036                 :            :                  * timer is serialized wrt itself.
    1037                 :            :                  */
    1038                 :          3 :                 if (likely(base->running_timer != timer)) {
    1039                 :            :                         /* See the comment in lock_timer_base() */
    1040                 :          3 :                         timer->flags |= TIMER_MIGRATING;
    1041                 :            : 
    1042                 :            :                         raw_spin_unlock(&base->lock);
    1043                 :            :                         base = new_base;
    1044                 :          3 :                         raw_spin_lock(&base->lock);
    1045                 :          3 :                         WRITE_ONCE(timer->flags,
    1046                 :            :                                    (timer->flags & ~TIMER_BASEMASK) | base->cpu);
    1047                 :          3 :                         forward_timer_base(base);
    1048                 :            :                 }
    1049                 :            :         }
    1050                 :            : 
    1051                 :            :         debug_timer_activate(timer);
    1052                 :            : 
    1053                 :          3 :         timer->expires = expires;
    1054                 :            :         /*
    1055                 :            :          * If 'idx' was calculated above and the base time did not advance
    1056                 :            :          * between calculating 'idx' and possibly switching the base, only
    1057                 :            :          * enqueue_timer() and trigger_dyntick_cpu() is required. Otherwise
    1058                 :            :          * we need to (re)calculate the wheel index via
    1059                 :            :          * internal_add_timer().
    1060                 :            :          */
    1061                 :          3 :         if (idx != UINT_MAX && clk == base->clk) {
    1062                 :          3 :                 enqueue_timer(base, timer, idx);
    1063                 :          3 :                 trigger_dyntick_cpu(base, timer);
    1064                 :            :         } else {
    1065                 :            :                 internal_add_timer(base, timer);
    1066                 :            :         }
    1067                 :            : 
    1068                 :            : out_unlock:
    1069                 :          3 :         raw_spin_unlock_irqrestore(&base->lock, flags);
    1070                 :            : 
    1071                 :          3 :         return ret;
    1072                 :            : }
    1073                 :            : 
    1074                 :            : /**
    1075                 :            :  * mod_timer_pending - modify a pending timer's timeout
    1076                 :            :  * @timer: the pending timer to be modified
    1077                 :            :  * @expires: new timeout in jiffies
    1078                 :            :  *
    1079                 :            :  * mod_timer_pending() is the same for pending timers as mod_timer(),
    1080                 :            :  * but will not re-activate and modify already deleted timers.
    1081                 :            :  *
    1082                 :            :  * It is useful for unserialized use of timers.
    1083                 :            :  */
    1084                 :          0 : int mod_timer_pending(struct timer_list *timer, unsigned long expires)
    1085                 :            : {
    1086                 :          0 :         return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
    1087                 :            : }
    1088                 :            : EXPORT_SYMBOL(mod_timer_pending);
    1089                 :            : 
    1090                 :            : /**
    1091                 :            :  * mod_timer - modify a timer's timeout
    1092                 :            :  * @timer: the timer to be modified
    1093                 :            :  * @expires: new timeout in jiffies
    1094                 :            :  *
    1095                 :            :  * mod_timer() is a more efficient way to update the expire field of an
    1096                 :            :  * active timer (if the timer is inactive it will be activated)
    1097                 :            :  *
    1098                 :            :  * mod_timer(timer, expires) is equivalent to:
    1099                 :            :  *
    1100                 :            :  *     del_timer(timer); timer->expires = expires; add_timer(timer);
    1101                 :            :  *
    1102                 :            :  * Note that if there are multiple unserialized concurrent users of the
    1103                 :            :  * same timer, then mod_timer() is the only safe way to modify the timeout,
    1104                 :            :  * since add_timer() cannot modify an already running timer.
    1105                 :            :  *
    1106                 :            :  * The function returns whether it has modified a pending timer or not.
    1107                 :            :  * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
    1108                 :            :  * active timer returns 1.)
    1109                 :            :  */
    1110                 :          3 : int mod_timer(struct timer_list *timer, unsigned long expires)
    1111                 :            : {
    1112                 :          3 :         return __mod_timer(timer, expires, 0);
    1113                 :            : }
    1114                 :            : EXPORT_SYMBOL(mod_timer);
    1115                 :            : 
    1116                 :            : /**
    1117                 :            :  * timer_reduce - Modify a timer's timeout if it would reduce the timeout
    1118                 :            :  * @timer:      The timer to be modified
    1119                 :            :  * @expires:    New timeout in jiffies
    1120                 :            :  *
    1121                 :            :  * timer_reduce() is very similar to mod_timer(), except that it will only
    1122                 :            :  * modify a running timer if that would reduce the expiration time (it will
    1123                 :            :  * start a timer that isn't running).
    1124                 :            :  */
    1125                 :          3 : int timer_reduce(struct timer_list *timer, unsigned long expires)
    1126                 :            : {
    1127                 :          3 :         return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
    1128                 :            : }
    1129                 :            : EXPORT_SYMBOL(timer_reduce);
    1130                 :            : 
    1131                 :            : /**
    1132                 :            :  * add_timer - start a timer
    1133                 :            :  * @timer: the timer to be added
    1134                 :            :  *
    1135                 :            :  * The kernel will do a ->function(@timer) callback from the
    1136                 :            :  * timer interrupt at the ->expires point in the future. The
    1137                 :            :  * current time is 'jiffies'.
    1138                 :            :  *
    1139                 :            :  * The timer's ->expires, ->function fields must be set prior calling this
    1140                 :            :  * function.
    1141                 :            :  *
    1142                 :            :  * Timers with an ->expires field in the past will be executed in the next
    1143                 :            :  * timer tick.
    1144                 :            :  */
    1145                 :          3 : void add_timer(struct timer_list *timer)
    1146                 :            : {
    1147                 :          3 :         BUG_ON(timer_pending(timer));
    1148                 :          3 :         mod_timer(timer, timer->expires);
    1149                 :          3 : }
    1150                 :            : EXPORT_SYMBOL(add_timer);
    1151                 :            : 
    1152                 :            : /**
    1153                 :            :  * add_timer_on - start a timer on a particular CPU
    1154                 :            :  * @timer: the timer to be added
    1155                 :            :  * @cpu: the CPU to start it on
    1156                 :            :  *
    1157                 :            :  * This is not very scalable on SMP. Double adds are not possible.
    1158                 :            :  */
    1159                 :          3 : void add_timer_on(struct timer_list *timer, int cpu)
    1160                 :            : {
    1161                 :            :         struct timer_base *new_base, *base;
    1162                 :            :         unsigned long flags;
    1163                 :            : 
    1164                 :          3 :         BUG_ON(timer_pending(timer) || !timer->function);
    1165                 :            : 
    1166                 :          3 :         new_base = get_timer_cpu_base(timer->flags, cpu);
    1167                 :            : 
    1168                 :            :         /*
    1169                 :            :          * If @timer was on a different CPU, it should be migrated with the
    1170                 :            :          * old base locked to prevent other operations proceeding with the
    1171                 :            :          * wrong base locked.  See lock_timer_base().
    1172                 :            :          */
    1173                 :          3 :         base = lock_timer_base(timer, &flags);
    1174                 :          3 :         if (base != new_base) {
    1175                 :          3 :                 timer->flags |= TIMER_MIGRATING;
    1176                 :            : 
    1177                 :            :                 raw_spin_unlock(&base->lock);
    1178                 :            :                 base = new_base;
    1179                 :          3 :                 raw_spin_lock(&base->lock);
    1180                 :          3 :                 WRITE_ONCE(timer->flags,
    1181                 :            :                            (timer->flags & ~TIMER_BASEMASK) | cpu);
    1182                 :            :         }
    1183                 :          3 :         forward_timer_base(base);
    1184                 :            : 
    1185                 :            :         debug_timer_activate(timer);
    1186                 :            :         internal_add_timer(base, timer);
    1187                 :          3 :         raw_spin_unlock_irqrestore(&base->lock, flags);
    1188                 :          3 : }
    1189                 :            : EXPORT_SYMBOL_GPL(add_timer_on);
    1190                 :            : 
    1191                 :            : /**
    1192                 :            :  * del_timer - deactivate a timer.
    1193                 :            :  * @timer: the timer to be deactivated
    1194                 :            :  *
    1195                 :            :  * del_timer() deactivates a timer - this works on both active and inactive
    1196                 :            :  * timers.
    1197                 :            :  *
    1198                 :            :  * The function returns whether it has deactivated a pending timer or not.
    1199                 :            :  * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
    1200                 :            :  * active timer returns 1.)
    1201                 :            :  */
    1202                 :          3 : int del_timer(struct timer_list *timer)
    1203                 :            : {
    1204                 :            :         struct timer_base *base;
    1205                 :            :         unsigned long flags;
    1206                 :            :         int ret = 0;
    1207                 :            : 
    1208                 :            :         debug_assert_init(timer);
    1209                 :            : 
    1210                 :          3 :         if (timer_pending(timer)) {
    1211                 :          3 :                 base = lock_timer_base(timer, &flags);
    1212                 :          3 :                 ret = detach_if_pending(timer, base, true);
    1213                 :          3 :                 raw_spin_unlock_irqrestore(&base->lock, flags);
    1214                 :            :         }
    1215                 :            : 
    1216                 :          3 :         return ret;
    1217                 :            : }
    1218                 :            : EXPORT_SYMBOL(del_timer);
    1219                 :            : 
    1220                 :            : /**
    1221                 :            :  * try_to_del_timer_sync - Try to deactivate a timer
    1222                 :            :  * @timer: timer to delete
    1223                 :            :  *
    1224                 :            :  * This function tries to deactivate a timer. Upon successful (ret >= 0)
    1225                 :            :  * exit the timer is not queued and the handler is not running on any CPU.
    1226                 :            :  */
    1227                 :          3 : int try_to_del_timer_sync(struct timer_list *timer)
    1228                 :            : {
    1229                 :            :         struct timer_base *base;
    1230                 :            :         unsigned long flags;
    1231                 :            :         int ret = -1;
    1232                 :            : 
    1233                 :            :         debug_assert_init(timer);
    1234                 :            : 
    1235                 :          3 :         base = lock_timer_base(timer, &flags);
    1236                 :            : 
    1237                 :          3 :         if (base->running_timer != timer)
    1238                 :          3 :                 ret = detach_if_pending(timer, base, true);
    1239                 :            : 
    1240                 :          3 :         raw_spin_unlock_irqrestore(&base->lock, flags);
    1241                 :            : 
    1242                 :          3 :         return ret;
    1243                 :            : }
    1244                 :            : EXPORT_SYMBOL(try_to_del_timer_sync);
    1245                 :            : 
    1246                 :            : #ifdef CONFIG_PREEMPT_RT
    1247                 :            : static __init void timer_base_init_expiry_lock(struct timer_base *base)
    1248                 :            : {
    1249                 :            :         spin_lock_init(&base->expiry_lock);
    1250                 :            : }
    1251                 :            : 
    1252                 :            : static inline void timer_base_lock_expiry(struct timer_base *base)
    1253                 :            : {
    1254                 :            :         spin_lock(&base->expiry_lock);
    1255                 :            : }
    1256                 :            : 
    1257                 :            : static inline void timer_base_unlock_expiry(struct timer_base *base)
    1258                 :            : {
    1259                 :            :         spin_unlock(&base->expiry_lock);
    1260                 :            : }
    1261                 :            : 
    1262                 :            : /*
    1263                 :            :  * The counterpart to del_timer_wait_running().
    1264                 :            :  *
    1265                 :            :  * If there is a waiter for base->expiry_lock, then it was waiting for the
    1266                 :            :  * timer callback to finish. Drop expiry_lock and reaquire it. That allows
    1267                 :            :  * the waiter to acquire the lock and make progress.
    1268                 :            :  */
    1269                 :            : static void timer_sync_wait_running(struct timer_base *base)
    1270                 :            : {
    1271                 :            :         if (atomic_read(&base->timer_waiters)) {
    1272                 :            :                 spin_unlock(&base->expiry_lock);
    1273                 :            :                 spin_lock(&base->expiry_lock);
    1274                 :            :         }
    1275                 :            : }
    1276                 :            : 
    1277                 :            : /*
    1278                 :            :  * This function is called on PREEMPT_RT kernels when the fast path
    1279                 :            :  * deletion of a timer failed because the timer callback function was
    1280                 :            :  * running.
    1281                 :            :  *
    1282                 :            :  * This prevents priority inversion, if the softirq thread on a remote CPU
    1283                 :            :  * got preempted, and it prevents a life lock when the task which tries to
    1284                 :            :  * delete a timer preempted the softirq thread running the timer callback
    1285                 :            :  * function.
    1286                 :            :  */
    1287                 :            : static void del_timer_wait_running(struct timer_list *timer)
    1288                 :            : {
    1289                 :            :         u32 tf;
    1290                 :            : 
    1291                 :            :         tf = READ_ONCE(timer->flags);
    1292                 :            :         if (!(tf & TIMER_MIGRATING)) {
    1293                 :            :                 struct timer_base *base = get_timer_base(tf);
    1294                 :            : 
    1295                 :            :                 /*
    1296                 :            :                  * Mark the base as contended and grab the expiry lock,
    1297                 :            :                  * which is held by the softirq across the timer
    1298                 :            :                  * callback. Drop the lock immediately so the softirq can
    1299                 :            :                  * expire the next timer. In theory the timer could already
    1300                 :            :                  * be running again, but that's more than unlikely and just
    1301                 :            :                  * causes another wait loop.
    1302                 :            :                  */
    1303                 :            :                 atomic_inc(&base->timer_waiters);
    1304                 :            :                 spin_lock_bh(&base->expiry_lock);
    1305                 :            :                 atomic_dec(&base->timer_waiters);
    1306                 :            :                 spin_unlock_bh(&base->expiry_lock);
    1307                 :            :         }
    1308                 :            : }
    1309                 :            : #else
    1310                 :            : static inline void timer_base_init_expiry_lock(struct timer_base *base) { }
    1311                 :            : static inline void timer_base_lock_expiry(struct timer_base *base) { }
    1312                 :            : static inline void timer_base_unlock_expiry(struct timer_base *base) { }
    1313                 :            : static inline void timer_sync_wait_running(struct timer_base *base) { }
    1314                 :            : static inline void del_timer_wait_running(struct timer_list *timer) { }
    1315                 :            : #endif
    1316                 :            : 
    1317                 :            : #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
    1318                 :            : /**
    1319                 :            :  * del_timer_sync - deactivate a timer and wait for the handler to finish.
    1320                 :            :  * @timer: the timer to be deactivated
    1321                 :            :  *
    1322                 :            :  * This function only differs from del_timer() on SMP: besides deactivating
    1323                 :            :  * the timer it also makes sure the handler has finished executing on other
    1324                 :            :  * CPUs.
    1325                 :            :  *
    1326                 :            :  * Synchronization rules: Callers must prevent restarting of the timer,
    1327                 :            :  * otherwise this function is meaningless. It must not be called from
    1328                 :            :  * interrupt contexts unless the timer is an irqsafe one. The caller must
    1329                 :            :  * not hold locks which would prevent completion of the timer's
    1330                 :            :  * handler. The timer's handler must not call add_timer_on(). Upon exit the
    1331                 :            :  * timer is not queued and the handler is not running on any CPU.
    1332                 :            :  *
    1333                 :            :  * Note: For !irqsafe timers, you must not hold locks that are held in
    1334                 :            :  *   interrupt context while calling this function. Even if the lock has
    1335                 :            :  *   nothing to do with the timer in question.  Here's why::
    1336                 :            :  *
    1337                 :            :  *    CPU0                             CPU1
    1338                 :            :  *    ----                             ----
    1339                 :            :  *                                     <SOFTIRQ>
    1340                 :            :  *                                       call_timer_fn();
    1341                 :            :  *                                       base->running_timer = mytimer;
    1342                 :            :  *    spin_lock_irq(somelock);
    1343                 :            :  *                                     <IRQ>
    1344                 :            :  *                                        spin_lock(somelock);
    1345                 :            :  *    del_timer_sync(mytimer);
    1346                 :            :  *    while (base->running_timer == mytimer);
    1347                 :            :  *
    1348                 :            :  * Now del_timer_sync() will never return and never release somelock.
    1349                 :            :  * The interrupt on the other CPU is waiting to grab somelock but
    1350                 :            :  * it has interrupted the softirq that CPU0 is waiting to finish.
    1351                 :            :  *
    1352                 :            :  * The function returns whether it has deactivated a pending timer or not.
    1353                 :            :  */
    1354                 :          3 : int del_timer_sync(struct timer_list *timer)
    1355                 :            : {
    1356                 :            :         int ret;
    1357                 :            : 
    1358                 :            : #ifdef CONFIG_LOCKDEP
    1359                 :            :         unsigned long flags;
    1360                 :            : 
    1361                 :            :         /*
    1362                 :            :          * If lockdep gives a backtrace here, please reference
    1363                 :            :          * the synchronization rules above.
    1364                 :            :          */
    1365                 :            :         local_irq_save(flags);
    1366                 :            :         lock_map_acquire(&timer->lockdep_map);
    1367                 :            :         lock_map_release(&timer->lockdep_map);
    1368                 :            :         local_irq_restore(flags);
    1369                 :            : #endif
    1370                 :            :         /*
    1371                 :            :          * don't use it in hardirq context, because it
    1372                 :            :          * could lead to deadlock.
    1373                 :            :          */
    1374                 :          3 :         WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
    1375                 :            : 
    1376                 :            :         do {
    1377                 :          3 :                 ret = try_to_del_timer_sync(timer);
    1378                 :            : 
    1379                 :          3 :                 if (unlikely(ret < 0)) {
    1380                 :            :                         del_timer_wait_running(timer);
    1381                 :          3 :                         cpu_relax();
    1382                 :            :                 }
    1383                 :          3 :         } while (ret < 0);
    1384                 :            : 
    1385                 :          3 :         return ret;
    1386                 :            : }
    1387                 :            : EXPORT_SYMBOL(del_timer_sync);
    1388                 :            : #endif
    1389                 :            : 
    1390                 :          3 : static void call_timer_fn(struct timer_list *timer,
    1391                 :            :                           void (*fn)(struct timer_list *),
    1392                 :            :                           unsigned long baseclk)
    1393                 :            : {
    1394                 :            :         int count = preempt_count();
    1395                 :            : 
    1396                 :            : #ifdef CONFIG_LOCKDEP
    1397                 :            :         /*
    1398                 :            :          * It is permissible to free the timer from inside the
    1399                 :            :          * function that is called from it, this we need to take into
    1400                 :            :          * account for lockdep too. To avoid bogus "held lock freed"
    1401                 :            :          * warnings as well as problems when looking into
    1402                 :            :          * timer->lockdep_map, make a copy and use that here.
    1403                 :            :          */
    1404                 :            :         struct lockdep_map lockdep_map;
    1405                 :            : 
    1406                 :            :         lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
    1407                 :            : #endif
    1408                 :            :         /*
    1409                 :            :          * Couple the lock chain with the lock chain at
    1410                 :            :          * del_timer_sync() by acquiring the lock_map around the fn()
    1411                 :            :          * call here and in del_timer_sync().
    1412                 :            :          */
    1413                 :            :         lock_map_acquire(&lockdep_map);
    1414                 :            : 
    1415                 :          3 :         trace_timer_expire_entry(timer, baseclk);
    1416                 :          3 :         fn(timer);
    1417                 :          3 :         trace_timer_expire_exit(timer);
    1418                 :            : 
    1419                 :            :         lock_map_release(&lockdep_map);
    1420                 :            : 
    1421                 :          3 :         if (count != preempt_count()) {
    1422                 :          0 :                 WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
    1423                 :            :                           fn, count, preempt_count());
    1424                 :            :                 /*
    1425                 :            :                  * Restore the preempt count. That gives us a decent
    1426                 :            :                  * chance to survive and extract information. If the
    1427                 :            :                  * callback kept a lock held, bad luck, but not worse
    1428                 :            :                  * than the BUG() we had.
    1429                 :            :                  */
    1430                 :            :                 preempt_count_set(count);
    1431                 :            :         }
    1432                 :          3 : }
    1433                 :            : 
    1434                 :          3 : static void expire_timers(struct timer_base *base, struct hlist_head *head)
    1435                 :            : {
    1436                 :            :         /*
    1437                 :            :          * This value is required only for tracing. base->clk was
    1438                 :            :          * incremented directly before expire_timers was called. But expiry
    1439                 :            :          * is related to the old base->clk value.
    1440                 :            :          */
    1441                 :          3 :         unsigned long baseclk = base->clk - 1;
    1442                 :            : 
    1443                 :          3 :         while (!hlist_empty(head)) {
    1444                 :            :                 struct timer_list *timer;
    1445                 :            :                 void (*fn)(struct timer_list *);
    1446                 :            : 
    1447                 :          3 :                 timer = hlist_entry(head->first, struct timer_list, entry);
    1448                 :            : 
    1449                 :          3 :                 base->running_timer = timer;
    1450                 :          3 :                 detach_timer(timer, true);
    1451                 :            : 
    1452                 :          3 :                 fn = timer->function;
    1453                 :            : 
    1454                 :          3 :                 if (timer->flags & TIMER_IRQSAFE) {
    1455                 :            :                         raw_spin_unlock(&base->lock);
    1456                 :          3 :                         call_timer_fn(timer, fn, baseclk);
    1457                 :          3 :                         base->running_timer = NULL;
    1458                 :          3 :                         raw_spin_lock(&base->lock);
    1459                 :            :                 } else {
    1460                 :          3 :                         raw_spin_unlock_irq(&base->lock);
    1461                 :          3 :                         call_timer_fn(timer, fn, baseclk);
    1462                 :          3 :                         base->running_timer = NULL;
    1463                 :            :                         timer_sync_wait_running(base);
    1464                 :          3 :                         raw_spin_lock_irq(&base->lock);
    1465                 :            :                 }
    1466                 :            :         }
    1467                 :          3 : }
    1468                 :            : 
    1469                 :          3 : static int __collect_expired_timers(struct timer_base *base,
    1470                 :            :                                     struct hlist_head *heads)
    1471                 :            : {
    1472                 :          3 :         unsigned long clk = base->clk;
    1473                 :            :         struct hlist_head *vec;
    1474                 :            :         int i, levels = 0;
    1475                 :            :         unsigned int idx;
    1476                 :            : 
    1477                 :          3 :         for (i = 0; i < LVL_DEPTH; i++) {
    1478                 :          3 :                 idx = (clk & LVL_MASK) + i * LVL_SIZE;
    1479                 :            : 
    1480                 :          3 :                 if (__test_and_clear_bit(idx, base->pending_map)) {
    1481                 :            :                         vec = base->vectors + idx;
    1482                 :          3 :                         hlist_move_list(vec, heads++);
    1483                 :          3 :                         levels++;
    1484                 :            :                 }
    1485                 :            :                 /* Is it time to look at the next level? */
    1486                 :          3 :                 if (clk & LVL_CLK_MASK)
    1487                 :            :                         break;
    1488                 :            :                 /* Shift clock for the next level granularity */
    1489                 :          3 :                 clk >>= LVL_CLK_SHIFT;
    1490                 :            :         }
    1491                 :          3 :         return levels;
    1492                 :            : }
    1493                 :            : 
    1494                 :            : #ifdef CONFIG_NO_HZ_COMMON
    1495                 :            : /*
    1496                 :            :  * Find the next pending bucket of a level. Search from level start (@offset)
    1497                 :            :  * + @clk upwards and if nothing there, search from start of the level
    1498                 :            :  * (@offset) up to @offset + clk.
    1499                 :            :  */
    1500                 :          3 : static int next_pending_bucket(struct timer_base *base, unsigned offset,
    1501                 :            :                                unsigned clk)
    1502                 :            : {
    1503                 :          3 :         unsigned pos, start = offset + clk;
    1504                 :          3 :         unsigned end = offset + LVL_SIZE;
    1505                 :            : 
    1506                 :          3 :         pos = find_next_bit(base->pending_map, end, start);
    1507                 :          3 :         if (pos < end)
    1508                 :          3 :                 return pos - start;
    1509                 :            : 
    1510                 :          3 :         pos = find_next_bit(base->pending_map, start, offset);
    1511                 :          3 :         return pos < start ? pos + LVL_SIZE - start : -1;
    1512                 :            : }
    1513                 :            : 
    1514                 :            : /*
    1515                 :            :  * Search the first expiring timer in the various clock levels. Caller must
    1516                 :            :  * hold base->lock.
    1517                 :            :  */
    1518                 :          3 : static unsigned long __next_timer_interrupt(struct timer_base *base)
    1519                 :            : {
    1520                 :            :         unsigned long clk, next, adj;
    1521                 :            :         unsigned lvl, offset = 0;
    1522                 :            : 
    1523                 :          3 :         next = base->clk + NEXT_TIMER_MAX_DELTA;
    1524                 :            :         clk = base->clk;
    1525                 :          3 :         for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
    1526                 :          3 :                 int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
    1527                 :            : 
    1528                 :          3 :                 if (pos >= 0) {
    1529                 :          3 :                         unsigned long tmp = clk + (unsigned long) pos;
    1530                 :            : 
    1531                 :          3 :                         tmp <<= LVL_SHIFT(lvl);
    1532                 :          3 :                         if (time_before(tmp, next))
    1533                 :            :                                 next = tmp;
    1534                 :            :                 }
    1535                 :            :                 /*
    1536                 :            :                  * Clock for the next level. If the current level clock lower
    1537                 :            :                  * bits are zero, we look at the next level as is. If not we
    1538                 :            :                  * need to advance it by one because that's going to be the
    1539                 :            :                  * next expiring bucket in that level. base->clk is the next
    1540                 :            :                  * expiring jiffie. So in case of:
    1541                 :            :                  *
    1542                 :            :                  * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
    1543                 :            :                  *  0    0    0    0    0    0
    1544                 :            :                  *
    1545                 :            :                  * we have to look at all levels @index 0. With
    1546                 :            :                  *
    1547                 :            :                  * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
    1548                 :            :                  *  0    0    0    0    0    2
    1549                 :            :                  *
    1550                 :            :                  * LVL0 has the next expiring bucket @index 2. The upper
    1551                 :            :                  * levels have the next expiring bucket @index 1.
    1552                 :            :                  *
    1553                 :            :                  * In case that the propagation wraps the next level the same
    1554                 :            :                  * rules apply:
    1555                 :            :                  *
    1556                 :            :                  * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
    1557                 :            :                  *  0    0    0    0    F    2
    1558                 :            :                  *
    1559                 :            :                  * So after looking at LVL0 we get:
    1560                 :            :                  *
    1561                 :            :                  * LVL5 LVL4 LVL3 LVL2 LVL1
    1562                 :            :                  *  0    0    0    1    0
    1563                 :            :                  *
    1564                 :            :                  * So no propagation from LVL1 to LVL2 because that happened
    1565                 :            :                  * with the add already, but then we need to propagate further
    1566                 :            :                  * from LVL2 to LVL3.
    1567                 :            :                  *
    1568                 :            :                  * So the simple check whether the lower bits of the current
    1569                 :            :                  * level are 0 or not is sufficient for all cases.
    1570                 :            :                  */
    1571                 :          3 :                 adj = clk & LVL_CLK_MASK ? 1 : 0;
    1572                 :          3 :                 clk >>= LVL_CLK_SHIFT;
    1573                 :          3 :                 clk += adj;
    1574                 :            :         }
    1575                 :          3 :         return next;
    1576                 :            : }
    1577                 :            : 
    1578                 :            : /*
    1579                 :            :  * Check, if the next hrtimer event is before the next timer wheel
    1580                 :            :  * event:
    1581                 :            :  */
    1582                 :          3 : static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
    1583                 :            : {
    1584                 :          3 :         u64 nextevt = hrtimer_get_next_event();
    1585                 :            : 
    1586                 :            :         /*
    1587                 :            :          * If high resolution timers are enabled
    1588                 :            :          * hrtimer_get_next_event() returns KTIME_MAX.
    1589                 :            :          */
    1590                 :          3 :         if (expires <= nextevt)
    1591                 :            :                 return expires;
    1592                 :            : 
    1593                 :            :         /*
    1594                 :            :          * If the next timer is already expired, return the tick base
    1595                 :            :          * time so the tick is fired immediately.
    1596                 :            :          */
    1597                 :          0 :         if (nextevt <= basem)
    1598                 :            :                 return basem;
    1599                 :            : 
    1600                 :            :         /*
    1601                 :            :          * Round up to the next jiffie. High resolution timers are
    1602                 :            :          * off, so the hrtimers are expired in the tick and we need to
    1603                 :            :          * make sure that this tick really expires the timer to avoid
    1604                 :            :          * a ping pong of the nohz stop code.
    1605                 :            :          *
    1606                 :            :          * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
    1607                 :            :          */
    1608                 :          0 :         return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
    1609                 :            : }
    1610                 :            : 
    1611                 :            : /**
    1612                 :            :  * get_next_timer_interrupt - return the time (clock mono) of the next timer
    1613                 :            :  * @basej:      base time jiffies
    1614                 :            :  * @basem:      base time clock monotonic
    1615                 :            :  *
    1616                 :            :  * Returns the tick aligned clock monotonic time of the next pending
    1617                 :            :  * timer or KTIME_MAX if no timer is pending.
    1618                 :            :  */
    1619                 :          3 : u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
    1620                 :            : {
    1621                 :          3 :         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
    1622                 :            :         u64 expires = KTIME_MAX;
    1623                 :            :         unsigned long nextevt;
    1624                 :            :         bool is_max_delta;
    1625                 :            : 
    1626                 :            :         /*
    1627                 :            :          * Pretend that there is no timer pending if the cpu is offline.
    1628                 :            :          * Possible pending timers will be migrated later to an active cpu.
    1629                 :            :          */
    1630                 :          3 :         if (cpu_is_offline(smp_processor_id()))
    1631                 :            :                 return expires;
    1632                 :            : 
    1633                 :          3 :         raw_spin_lock(&base->lock);
    1634                 :          3 :         nextevt = __next_timer_interrupt(base);
    1635                 :          3 :         is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA);
    1636                 :          3 :         base->next_expiry = nextevt;
    1637                 :            :         /*
    1638                 :            :          * We have a fresh next event. Check whether we can forward the
    1639                 :            :          * base. We can only do that when @basej is past base->clk
    1640                 :            :          * otherwise we might rewind base->clk.
    1641                 :            :          */
    1642                 :          3 :         if (time_after(basej, base->clk)) {
    1643                 :          3 :                 if (time_after(nextevt, basej))
    1644                 :          3 :                         base->clk = basej;
    1645                 :          3 :                 else if (time_after(nextevt, base->clk))
    1646                 :          3 :                         base->clk = nextevt;
    1647                 :            :         }
    1648                 :            : 
    1649                 :          3 :         if (time_before_eq(nextevt, basej)) {
    1650                 :            :                 expires = basem;
    1651                 :          3 :                 base->is_idle = false;
    1652                 :            :         } else {
    1653                 :          3 :                 if (!is_max_delta)
    1654                 :          3 :                         expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
    1655                 :            :                 /*
    1656                 :            :                  * If we expect to sleep more than a tick, mark the base idle.
    1657                 :            :                  * Also the tick is stopped so any added timer must forward
    1658                 :            :                  * the base clk itself to keep granularity small. This idle
    1659                 :            :                  * logic is only maintained for the BASE_STD base, deferrable
    1660                 :            :                  * timers may still see large granularity skew (by design).
    1661                 :            :                  */
    1662                 :          3 :                 if ((expires - basem) > TICK_NSEC) {
    1663                 :          3 :                         base->must_forward_clk = true;
    1664                 :          3 :                         base->is_idle = true;
    1665                 :            :                 }
    1666                 :            :         }
    1667                 :            :         raw_spin_unlock(&base->lock);
    1668                 :            : 
    1669                 :          3 :         return cmp_next_hrtimer_event(basem, expires);
    1670                 :            : }
    1671                 :            : 
    1672                 :            : /**
    1673                 :            :  * timer_clear_idle - Clear the idle state of the timer base
    1674                 :            :  *
    1675                 :            :  * Called with interrupts disabled
    1676                 :            :  */
    1677                 :          3 : void timer_clear_idle(void)
    1678                 :            : {
    1679                 :          3 :         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
    1680                 :            : 
    1681                 :            :         /*
    1682                 :            :          * We do this unlocked. The worst outcome is a remote enqueue sending
    1683                 :            :          * a pointless IPI, but taking the lock would just make the window for
    1684                 :            :          * sending the IPI a few instructions smaller for the cost of taking
    1685                 :            :          * the lock in the exit from idle path.
    1686                 :            :          */
    1687                 :          3 :         base->is_idle = false;
    1688                 :          3 : }
    1689                 :            : 
    1690                 :          3 : static int collect_expired_timers(struct timer_base *base,
    1691                 :            :                                   struct hlist_head *heads)
    1692                 :            : {
    1693                 :          3 :         unsigned long now = READ_ONCE(jiffies);
    1694                 :            : 
    1695                 :            :         /*
    1696                 :            :          * NOHZ optimization. After a long idle sleep we need to forward the
    1697                 :            :          * base to current jiffies. Avoid a loop by searching the bitfield for
    1698                 :            :          * the next expiring timer.
    1699                 :            :          */
    1700                 :          3 :         if ((long)(now - base->clk) > 2) {
    1701                 :          3 :                 unsigned long next = __next_timer_interrupt(base);
    1702                 :            : 
    1703                 :            :                 /*
    1704                 :            :                  * If the next timer is ahead of time forward to current
    1705                 :            :                  * jiffies, otherwise forward to the next expiry time:
    1706                 :            :                  */
    1707                 :          3 :                 if (time_after(next, now)) {
    1708                 :            :                         /*
    1709                 :            :                          * The call site will increment base->clk and then
    1710                 :            :                          * terminate the expiry loop immediately.
    1711                 :            :                          */
    1712                 :          3 :                         base->clk = now;
    1713                 :          3 :                         return 0;
    1714                 :            :                 }
    1715                 :          3 :                 base->clk = next;
    1716                 :            :         }
    1717                 :          3 :         return __collect_expired_timers(base, heads);
    1718                 :            : }
    1719                 :            : #else
    1720                 :            : static inline int collect_expired_timers(struct timer_base *base,
    1721                 :            :                                          struct hlist_head *heads)
    1722                 :            : {
    1723                 :            :         return __collect_expired_timers(base, heads);
    1724                 :            : }
    1725                 :            : #endif
    1726                 :            : 
    1727                 :            : /*
    1728                 :            :  * Called from the timer interrupt handler to charge one tick to the current
    1729                 :            :  * process.  user_tick is 1 if the tick is user time, 0 for system.
    1730                 :            :  */
    1731                 :          3 : void update_process_times(int user_tick)
    1732                 :            : {
    1733                 :          3 :         struct task_struct *p = current;
    1734                 :            : 
    1735                 :            :         /* Note: this timer irq context must be accounted for as well. */
    1736                 :          3 :         account_process_tick(p, user_tick);
    1737                 :          3 :         run_local_timers();
    1738                 :          3 :         rcu_sched_clock_irq(user_tick);
    1739                 :            : #ifdef CONFIG_IRQ_WORK
    1740                 :          3 :         if (in_irq())
    1741                 :          3 :                 irq_work_tick();
    1742                 :            : #endif
    1743                 :          3 :         scheduler_tick();
    1744                 :            :         if (IS_ENABLED(CONFIG_POSIX_TIMERS))
    1745                 :          3 :                 run_posix_cpu_timers();
    1746                 :            : 
    1747                 :            :         /* The current CPU might make use of net randoms without receiving IRQs
    1748                 :            :          * to renew them often enough. Let's update the net_rand_state from a
    1749                 :            :          * non-constant value that's not affine to the number of calls to make
    1750                 :            :          * sure it's updated when there's some activity (we don't care in idle).
    1751                 :            :          */
    1752                 :          3 :         this_cpu_add(net_rand_state.s1, rol32(jiffies, 24) + user_tick);
    1753                 :          3 : }
    1754                 :            : 
    1755                 :            : /**
    1756                 :            :  * __run_timers - run all expired timers (if any) on this CPU.
    1757                 :            :  * @base: the timer vector to be processed.
    1758                 :            :  */
    1759                 :          3 : static inline void __run_timers(struct timer_base *base)
    1760                 :            : {
    1761                 :            :         struct hlist_head heads[LVL_DEPTH];
    1762                 :            :         int levels;
    1763                 :            : 
    1764                 :          3 :         if (!time_after_eq(jiffies, base->clk))
    1765                 :          3 :                 return;
    1766                 :            : 
    1767                 :            :         timer_base_lock_expiry(base);
    1768                 :          3 :         raw_spin_lock_irq(&base->lock);
    1769                 :            : 
    1770                 :            :         /*
    1771                 :            :          * timer_base::must_forward_clk must be cleared before running
    1772                 :            :          * timers so that any timer functions that call mod_timer() will
    1773                 :            :          * not try to forward the base. Idle tracking / clock forwarding
    1774                 :            :          * logic is only used with BASE_STD timers.
    1775                 :            :          *
    1776                 :            :          * The must_forward_clk flag is cleared unconditionally also for
    1777                 :            :          * the deferrable base. The deferrable base is not affected by idle
    1778                 :            :          * tracking and never forwarded, so clearing the flag is a NOOP.
    1779                 :            :          *
    1780                 :            :          * The fact that the deferrable base is never forwarded can cause
    1781                 :            :          * large variations in granularity for deferrable timers, but they
    1782                 :            :          * can be deferred for long periods due to idle anyway.
    1783                 :            :          */
    1784                 :          3 :         base->must_forward_clk = false;
    1785                 :            : 
    1786                 :          3 :         while (time_after_eq(jiffies, base->clk)) {
    1787                 :            : 
    1788                 :          3 :                 levels = collect_expired_timers(base, heads);
    1789                 :          3 :                 base->clk++;
    1790                 :            : 
    1791                 :          3 :                 while (levels--)
    1792                 :          3 :                         expire_timers(base, heads + levels);
    1793                 :            :         }
    1794                 :          3 :         raw_spin_unlock_irq(&base->lock);
    1795                 :            :         timer_base_unlock_expiry(base);
    1796                 :            : }
    1797                 :            : 
    1798                 :            : /*
    1799                 :            :  * This function runs timers and the timer-tq in bottom half context.
    1800                 :            :  */
    1801                 :          3 : static __latent_entropy void run_timer_softirq(struct softirq_action *h)
    1802                 :            : {
    1803                 :          3 :         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
    1804                 :            : 
    1805                 :          3 :         __run_timers(base);
    1806                 :            :         if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
    1807                 :          3 :                 __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
    1808                 :          3 : }
    1809                 :            : 
    1810                 :            : /*
    1811                 :            :  * Called by the local, per-CPU timer interrupt on SMP.
    1812                 :            :  */
    1813                 :          3 : void run_local_timers(void)
    1814                 :            : {
    1815                 :          3 :         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
    1816                 :            : 
    1817                 :          3 :         hrtimer_run_queues();
    1818                 :            :         /* Raise the softirq only if required. */
    1819                 :          3 :         if (time_before(jiffies, base->clk)) {
    1820                 :            :                 if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
    1821                 :            :                         return;
    1822                 :            :                 /* CPU is awake, so check the deferrable base. */
    1823                 :            :                 base++;
    1824                 :          3 :                 if (time_before(jiffies, base->clk))
    1825                 :            :                         return;
    1826                 :            :         }
    1827                 :          3 :         raise_softirq(TIMER_SOFTIRQ);
    1828                 :            : }
    1829                 :            : 
    1830                 :            : /*
    1831                 :            :  * Since schedule_timeout()'s timer is defined on the stack, it must store
    1832                 :            :  * the target task on the stack as well.
    1833                 :            :  */
    1834                 :            : struct process_timer {
    1835                 :            :         struct timer_list timer;
    1836                 :            :         struct task_struct *task;
    1837                 :            : };
    1838                 :            : 
    1839                 :          3 : static void process_timeout(struct timer_list *t)
    1840                 :            : {
    1841                 :            :         struct process_timer *timeout = from_timer(timeout, t, timer);
    1842                 :            : 
    1843                 :          3 :         wake_up_process(timeout->task);
    1844                 :          3 : }
    1845                 :            : 
    1846                 :            : /**
    1847                 :            :  * schedule_timeout - sleep until timeout
    1848                 :            :  * @timeout: timeout value in jiffies
    1849                 :            :  *
    1850                 :            :  * Make the current task sleep until @timeout jiffies have
    1851                 :            :  * elapsed. The routine will return immediately unless
    1852                 :            :  * the current task state has been set (see set_current_state()).
    1853                 :            :  *
    1854                 :            :  * You can set the task state as follows -
    1855                 :            :  *
    1856                 :            :  * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
    1857                 :            :  * pass before the routine returns unless the current task is explicitly
    1858                 :            :  * woken up, (e.g. by wake_up_process())".
    1859                 :            :  *
    1860                 :            :  * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
    1861                 :            :  * delivered to the current task or the current task is explicitly woken
    1862                 :            :  * up.
    1863                 :            :  *
    1864                 :            :  * The current task state is guaranteed to be TASK_RUNNING when this
    1865                 :            :  * routine returns.
    1866                 :            :  *
    1867                 :            :  * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
    1868                 :            :  * the CPU away without a bound on the timeout. In this case the return
    1869                 :            :  * value will be %MAX_SCHEDULE_TIMEOUT.
    1870                 :            :  *
    1871                 :            :  * Returns 0 when the timer has expired otherwise the remaining time in
    1872                 :            :  * jiffies will be returned.  In all cases the return value is guaranteed
    1873                 :            :  * to be non-negative.
    1874                 :            :  */
    1875                 :          3 : signed long __sched schedule_timeout(signed long timeout)
    1876                 :            : {
    1877                 :            :         struct process_timer timer;
    1878                 :            :         unsigned long expire;
    1879                 :            : 
    1880                 :          3 :         switch (timeout)
    1881                 :            :         {
    1882                 :            :         case MAX_SCHEDULE_TIMEOUT:
    1883                 :            :                 /*
    1884                 :            :                  * These two special cases are useful to be comfortable
    1885                 :            :                  * in the caller. Nothing more. We could take
    1886                 :            :                  * MAX_SCHEDULE_TIMEOUT from one of the negative value
    1887                 :            :                  * but I' d like to return a valid offset (>=0) to allow
    1888                 :            :                  * the caller to do everything it want with the retval.
    1889                 :            :                  */
    1890                 :          3 :                 schedule();
    1891                 :          3 :                 goto out;
    1892                 :            :         default:
    1893                 :            :                 /*
    1894                 :            :                  * Another bit of PARANOID. Note that the retval will be
    1895                 :            :                  * 0 since no piece of kernel is supposed to do a check
    1896                 :            :                  * for a negative retval of schedule_timeout() (since it
    1897                 :            :                  * should never happens anyway). You just have the printk()
    1898                 :            :                  * that will tell you if something is gone wrong and where.
    1899                 :            :                  */
    1900                 :          3 :                 if (timeout < 0) {
    1901                 :          0 :                         printk(KERN_ERR "schedule_timeout: wrong timeout "
    1902                 :            :                                 "value %lx\n", timeout);
    1903                 :          0 :                         dump_stack();
    1904                 :          0 :                         current->state = TASK_RUNNING;
    1905                 :          0 :                         goto out;
    1906                 :            :                 }
    1907                 :            :         }
    1908                 :            : 
    1909                 :          3 :         expire = timeout + jiffies;
    1910                 :            : 
    1911                 :          3 :         timer.task = current;
    1912                 :            :         timer_setup_on_stack(&timer.timer, process_timeout, 0);
    1913                 :          3 :         __mod_timer(&timer.timer, expire, 0);
    1914                 :          3 :         schedule();
    1915                 :          3 :         del_singleshot_timer_sync(&timer.timer);
    1916                 :            : 
    1917                 :            :         /* Remove the timer from the object tracker */
    1918                 :            :         destroy_timer_on_stack(&timer.timer);
    1919                 :            : 
    1920                 :          3 :         timeout = expire - jiffies;
    1921                 :            : 
    1922                 :            :  out:
    1923                 :          3 :         return timeout < 0 ? 0 : timeout;
    1924                 :            : }
    1925                 :            : EXPORT_SYMBOL(schedule_timeout);
    1926                 :            : 
    1927                 :            : /*
    1928                 :            :  * We can use __set_current_state() here because schedule_timeout() calls
    1929                 :            :  * schedule() unconditionally.
    1930                 :            :  */
    1931                 :          3 : signed long __sched schedule_timeout_interruptible(signed long timeout)
    1932                 :            : {
    1933                 :          3 :         __set_current_state(TASK_INTERRUPTIBLE);
    1934                 :          3 :         return schedule_timeout(timeout);
    1935                 :            : }
    1936                 :            : EXPORT_SYMBOL(schedule_timeout_interruptible);
    1937                 :            : 
    1938                 :          0 : signed long __sched schedule_timeout_killable(signed long timeout)
    1939                 :            : {
    1940                 :          0 :         __set_current_state(TASK_KILLABLE);
    1941                 :          0 :         return schedule_timeout(timeout);
    1942                 :            : }
    1943                 :            : EXPORT_SYMBOL(schedule_timeout_killable);
    1944                 :            : 
    1945                 :          0 : signed long __sched schedule_timeout_uninterruptible(signed long timeout)
    1946                 :            : {
    1947                 :          3 :         __set_current_state(TASK_UNINTERRUPTIBLE);
    1948                 :          3 :         return schedule_timeout(timeout);
    1949                 :            : }
    1950                 :            : EXPORT_SYMBOL(schedule_timeout_uninterruptible);
    1951                 :            : 
    1952                 :            : /*
    1953                 :            :  * Like schedule_timeout_uninterruptible(), except this task will not contribute
    1954                 :            :  * to load average.
    1955                 :            :  */
    1956                 :          0 : signed long __sched schedule_timeout_idle(signed long timeout)
    1957                 :            : {
    1958                 :          0 :         __set_current_state(TASK_IDLE);
    1959                 :          0 :         return schedule_timeout(timeout);
    1960                 :            : }
    1961                 :            : EXPORT_SYMBOL(schedule_timeout_idle);
    1962                 :            : 
    1963                 :            : #ifdef CONFIG_HOTPLUG_CPU
    1964                 :            : static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
    1965                 :            : {
    1966                 :            :         struct timer_list *timer;
    1967                 :            :         int cpu = new_base->cpu;
    1968                 :            : 
    1969                 :            :         while (!hlist_empty(head)) {
    1970                 :            :                 timer = hlist_entry(head->first, struct timer_list, entry);
    1971                 :            :                 detach_timer(timer, false);
    1972                 :            :                 timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
    1973                 :            :                 internal_add_timer(new_base, timer);
    1974                 :            :         }
    1975                 :            : }
    1976                 :            : 
    1977                 :            : int timers_prepare_cpu(unsigned int cpu)
    1978                 :            : {
    1979                 :            :         struct timer_base *base;
    1980                 :            :         int b;
    1981                 :            : 
    1982                 :            :         for (b = 0; b < NR_BASES; b++) {
    1983                 :            :                 base = per_cpu_ptr(&timer_bases[b], cpu);
    1984                 :            :                 base->clk = jiffies;
    1985                 :            :                 base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
    1986                 :            :                 base->is_idle = false;
    1987                 :            :                 base->must_forward_clk = true;
    1988                 :            :         }
    1989                 :            :         return 0;
    1990                 :            : }
    1991                 :            : 
    1992                 :            : int timers_dead_cpu(unsigned int cpu)
    1993                 :            : {
    1994                 :            :         struct timer_base *old_base;
    1995                 :            :         struct timer_base *new_base;
    1996                 :            :         int b, i;
    1997                 :            : 
    1998                 :            :         BUG_ON(cpu_online(cpu));
    1999                 :            : 
    2000                 :            :         for (b = 0; b < NR_BASES; b++) {
    2001                 :            :                 old_base = per_cpu_ptr(&timer_bases[b], cpu);
    2002                 :            :                 new_base = get_cpu_ptr(&timer_bases[b]);
    2003                 :            :                 /*
    2004                 :            :                  * The caller is globally serialized and nobody else
    2005                 :            :                  * takes two locks at once, deadlock is not possible.
    2006                 :            :                  */
    2007                 :            :                 raw_spin_lock_irq(&new_base->lock);
    2008                 :            :                 raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
    2009                 :            : 
    2010                 :            :                 /*
    2011                 :            :                  * The current CPUs base clock might be stale. Update it
    2012                 :            :                  * before moving the timers over.
    2013                 :            :                  */
    2014                 :            :                 forward_timer_base(new_base);
    2015                 :            : 
    2016                 :            :                 BUG_ON(old_base->running_timer);
    2017                 :            : 
    2018                 :            :                 for (i = 0; i < WHEEL_SIZE; i++)
    2019                 :            :                         migrate_timer_list(new_base, old_base->vectors + i);
    2020                 :            : 
    2021                 :            :                 raw_spin_unlock(&old_base->lock);
    2022                 :            :                 raw_spin_unlock_irq(&new_base->lock);
    2023                 :            :                 put_cpu_ptr(&timer_bases);
    2024                 :            :         }
    2025                 :            :         return 0;
    2026                 :            : }
    2027                 :            : 
    2028                 :            : #endif /* CONFIG_HOTPLUG_CPU */
    2029                 :            : 
    2030                 :          3 : static void __init init_timer_cpu(int cpu)
    2031                 :            : {
    2032                 :            :         struct timer_base *base;
    2033                 :            :         int i;
    2034                 :            : 
    2035                 :          3 :         for (i = 0; i < NR_BASES; i++) {
    2036                 :          3 :                 base = per_cpu_ptr(&timer_bases[i], cpu);
    2037                 :          3 :                 base->cpu = cpu;
    2038                 :          3 :                 raw_spin_lock_init(&base->lock);
    2039                 :          3 :                 base->clk = jiffies;
    2040                 :            :                 timer_base_init_expiry_lock(base);
    2041                 :            :         }
    2042                 :          3 : }
    2043                 :            : 
    2044                 :          3 : static void __init init_timer_cpus(void)
    2045                 :            : {
    2046                 :            :         int cpu;
    2047                 :            : 
    2048                 :          3 :         for_each_possible_cpu(cpu)
    2049                 :          3 :                 init_timer_cpu(cpu);
    2050                 :          3 : }
    2051                 :            : 
    2052                 :          3 : void __init init_timers(void)
    2053                 :            : {
    2054                 :          3 :         init_timer_cpus();
    2055                 :          3 :         open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
    2056                 :          3 : }
    2057                 :            : 
    2058                 :            : /**
    2059                 :            :  * msleep - sleep safely even with waitqueue interruptions
    2060                 :            :  * @msecs: Time in milliseconds to sleep for
    2061                 :            :  */
    2062                 :          3 : void msleep(unsigned int msecs)
    2063                 :            : {
    2064                 :          3 :         unsigned long timeout = msecs_to_jiffies(msecs) + 1;
    2065                 :            : 
    2066                 :          3 :         while (timeout)
    2067                 :          3 :                 timeout = schedule_timeout_uninterruptible(timeout);
    2068                 :          3 : }
    2069                 :            : 
    2070                 :            : EXPORT_SYMBOL(msleep);
    2071                 :            : 
    2072                 :            : /**
    2073                 :            :  * msleep_interruptible - sleep waiting for signals
    2074                 :            :  * @msecs: Time in milliseconds to sleep for
    2075                 :            :  */
    2076                 :          2 : unsigned long msleep_interruptible(unsigned int msecs)
    2077                 :            : {
    2078                 :          2 :         unsigned long timeout = msecs_to_jiffies(msecs) + 1;
    2079                 :            : 
    2080                 :          2 :         while (timeout && !signal_pending(current))
    2081                 :          2 :                 timeout = schedule_timeout_interruptible(timeout);
    2082                 :          2 :         return jiffies_to_msecs(timeout);
    2083                 :            : }
    2084                 :            : 
    2085                 :            : EXPORT_SYMBOL(msleep_interruptible);
    2086                 :            : 
    2087                 :            : /**
    2088                 :            :  * usleep_range - Sleep for an approximate time
    2089                 :            :  * @min: Minimum time in usecs to sleep
    2090                 :            :  * @max: Maximum time in usecs to sleep
    2091                 :            :  *
    2092                 :            :  * In non-atomic context where the exact wakeup time is flexible, use
    2093                 :            :  * usleep_range() instead of udelay().  The sleep improves responsiveness
    2094                 :            :  * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
    2095                 :            :  * power usage by allowing hrtimers to take advantage of an already-
    2096                 :            :  * scheduled interrupt instead of scheduling a new one just for this sleep.
    2097                 :            :  */
    2098                 :          3 : void __sched usleep_range(unsigned long min, unsigned long max)
    2099                 :            : {
    2100                 :          3 :         ktime_t exp = ktime_add_us(ktime_get(), min);
    2101                 :          3 :         u64 delta = (u64)(max - min) * NSEC_PER_USEC;
    2102                 :            : 
    2103                 :            :         for (;;) {
    2104                 :          3 :                 __set_current_state(TASK_UNINTERRUPTIBLE);
    2105                 :            :                 /* Do not return before the requested sleep time has elapsed */
    2106                 :          3 :                 if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
    2107                 :            :                         break;
    2108                 :            :         }
    2109                 :          3 : }
    2110                 :            : EXPORT_SYMBOL(usleep_range);
    

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