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       1                 :            : /* SPDX-License-Identifier: GPL-2.0+ */
       2                 :            : /*
       3                 :            :  * Sleepable Read-Copy Update mechanism for mutual exclusion
       4                 :            :  *
       5                 :            :  * Copyright (C) IBM Corporation, 2006
       6                 :            :  * Copyright (C) Fujitsu, 2012
       7                 :            :  *
       8                 :            :  * Author: Paul McKenney <paulmck@linux.ibm.com>
       9                 :            :  *         Lai Jiangshan <laijs@cn.fujitsu.com>
      10                 :            :  *
      11                 :            :  * For detailed explanation of Read-Copy Update mechanism see -
      12                 :            :  *              Documentation/RCU/ *.txt
      13                 :            :  *
      14                 :            :  */
      15                 :            : 
      16                 :            : #ifndef _LINUX_SRCU_H
      17                 :            : #define _LINUX_SRCU_H
      18                 :            : 
      19                 :            : #include <linux/mutex.h>
      20                 :            : #include <linux/rcupdate.h>
      21                 :            : #include <linux/workqueue.h>
      22                 :            : #include <linux/rcu_segcblist.h>
      23                 :            : 
      24                 :            : struct srcu_struct;
      25                 :            : 
      26                 :            : #ifdef CONFIG_DEBUG_LOCK_ALLOC
      27                 :            : 
      28                 :            : int __init_srcu_struct(struct srcu_struct *ssp, const char *name,
      29                 :            :                        struct lock_class_key *key);
      30                 :            : 
      31                 :            : #define init_srcu_struct(ssp) \
      32                 :            : ({ \
      33                 :            :         static struct lock_class_key __srcu_key; \
      34                 :            :         \
      35                 :            :         __init_srcu_struct((ssp), #ssp, &__srcu_key); \
      36                 :            : })
      37                 :            : 
      38                 :            : #define __SRCU_DEP_MAP_INIT(srcu_name)  .dep_map = { .name = #srcu_name },
      39                 :            : #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
      40                 :            : 
      41                 :            : int init_srcu_struct(struct srcu_struct *ssp);
      42                 :            : 
      43                 :            : #define __SRCU_DEP_MAP_INIT(srcu_name)
      44                 :            : #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
      45                 :            : 
      46                 :            : #ifdef CONFIG_TINY_SRCU
      47                 :            : #include <linux/srcutiny.h>
      48                 :            : #elif defined(CONFIG_TREE_SRCU)
      49                 :            : #include <linux/srcutree.h>
      50                 :            : #elif defined(CONFIG_SRCU)
      51                 :            : #error "Unknown SRCU implementation specified to kernel configuration"
      52                 :            : #else
      53                 :            : /* Dummy definition for things like notifiers.  Actual use gets link error. */
      54                 :            : struct srcu_struct { };
      55                 :            : #endif
      56                 :            : 
      57                 :            : void call_srcu(struct srcu_struct *ssp, struct rcu_head *head,
      58                 :            :                 void (*func)(struct rcu_head *head));
      59                 :            : void cleanup_srcu_struct(struct srcu_struct *ssp);
      60                 :            : int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp);
      61                 :            : void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
      62                 :            : void synchronize_srcu(struct srcu_struct *ssp);
      63                 :            : 
      64                 :            : #ifdef CONFIG_DEBUG_LOCK_ALLOC
      65                 :            : 
      66                 :            : /**
      67                 :            :  * srcu_read_lock_held - might we be in SRCU read-side critical section?
      68                 :            :  * @ssp: The srcu_struct structure to check
      69                 :            :  *
      70                 :            :  * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
      71                 :            :  * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
      72                 :            :  * this assumes we are in an SRCU read-side critical section unless it can
      73                 :            :  * prove otherwise.
      74                 :            :  *
      75                 :            :  * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
      76                 :            :  * and while lockdep is disabled.
      77                 :            :  *
      78                 :            :  * Note that SRCU is based on its own statemachine and it doesn't
      79                 :            :  * relies on normal RCU, it can be called from the CPU which
      80                 :            :  * is in the idle loop from an RCU point of view or offline.
      81                 :            :  */
      82                 :            : static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
      83                 :            : {
      84                 :            :         if (!debug_lockdep_rcu_enabled())
      85                 :            :                 return 1;
      86                 :            :         return lock_is_held(&ssp->dep_map);
      87                 :            : }
      88                 :            : 
      89                 :            : #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
      90                 :            : 
      91                 :        221 : static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
      92                 :            : {
      93                 :        221 :         return 1;
      94                 :            : }
      95                 :            : 
      96                 :            : #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
      97                 :            : 
      98                 :            : /**
      99                 :            :  * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
     100                 :            :  * @p: the pointer to fetch and protect for later dereferencing
     101                 :            :  * @ssp: pointer to the srcu_struct, which is used to check that we
     102                 :            :  *      really are in an SRCU read-side critical section.
     103                 :            :  * @c: condition to check for update-side use
     104                 :            :  *
     105                 :            :  * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
     106                 :            :  * critical section will result in an RCU-lockdep splat, unless @c evaluates
     107                 :            :  * to 1.  The @c argument will normally be a logical expression containing
     108                 :            :  * lockdep_is_held() calls.
     109                 :            :  */
     110                 :            : #define srcu_dereference_check(p, ssp, c) \
     111                 :            :         __rcu_dereference_check((p), (c) || srcu_read_lock_held(ssp), __rcu)
     112                 :            : 
     113                 :            : /**
     114                 :            :  * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
     115                 :            :  * @p: the pointer to fetch and protect for later dereferencing
     116                 :            :  * @ssp: pointer to the srcu_struct, which is used to check that we
     117                 :            :  *      really are in an SRCU read-side critical section.
     118                 :            :  *
     119                 :            :  * Makes rcu_dereference_check() do the dirty work.  If PROVE_RCU
     120                 :            :  * is enabled, invoking this outside of an RCU read-side critical
     121                 :            :  * section will result in an RCU-lockdep splat.
     122                 :            :  */
     123                 :            : #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0)
     124                 :            : 
     125                 :            : /**
     126                 :            :  * srcu_dereference_notrace - no tracing and no lockdep calls from here
     127                 :            :  * @p: the pointer to fetch and protect for later dereferencing
     128                 :            :  * @ssp: pointer to the srcu_struct, which is used to check that we
     129                 :            :  *      really are in an SRCU read-side critical section.
     130                 :            :  */
     131                 :            : #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1)
     132                 :            : 
     133                 :            : /**
     134                 :            :  * srcu_read_lock - register a new reader for an SRCU-protected structure.
     135                 :            :  * @ssp: srcu_struct in which to register the new reader.
     136                 :            :  *
     137                 :            :  * Enter an SRCU read-side critical section.  Note that SRCU read-side
     138                 :            :  * critical sections may be nested.  However, it is illegal to
     139                 :            :  * call anything that waits on an SRCU grace period for the same
     140                 :            :  * srcu_struct, whether directly or indirectly.  Please note that
     141                 :            :  * one way to indirectly wait on an SRCU grace period is to acquire
     142                 :            :  * a mutex that is held elsewhere while calling synchronize_srcu() or
     143                 :            :  * synchronize_srcu_expedited().
     144                 :            :  *
     145                 :            :  * Note that srcu_read_lock() and the matching srcu_read_unlock() must
     146                 :            :  * occur in the same context, for example, it is illegal to invoke
     147                 :            :  * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
     148                 :            :  * was invoked in process context.
     149                 :            :  */
     150                 :     103979 : static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
     151                 :            : {
     152                 :     103979 :         int retval;
     153                 :            : 
     154                 :     103979 :         retval = __srcu_read_lock(ssp);
     155                 :     103979 :         rcu_lock_acquire(&(ssp)->dep_map);
     156   [ +  +  #  #  :     103160 :         return retval;
          #  #  #  #  #  
          #  #  #  #  #  
             #  #  #  # ]
     157                 :            : }
     158                 :            : 
     159                 :            : /* Used by tracing, cannot be traced and cannot invoke lockdep. */
     160                 :            : static inline notrace int
     161                 :          0 : srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
     162                 :            : {
     163                 :          0 :         int retval;
     164                 :            : 
     165                 :          0 :         retval = __srcu_read_lock(ssp);
     166                 :          0 :         return retval;
     167                 :            : }
     168                 :            : 
     169                 :            : /**
     170                 :            :  * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
     171                 :            :  * @ssp: srcu_struct in which to unregister the old reader.
     172                 :            :  * @idx: return value from corresponding srcu_read_lock().
     173                 :            :  *
     174                 :            :  * Exit an SRCU read-side critical section.
     175                 :            :  */
     176                 :     103979 : static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
     177                 :            :         __releases(ssp)
     178                 :            : {
     179         [ -  + ]:     103979 :         WARN_ON_ONCE(idx & ~0x1);
     180                 :     103979 :         rcu_lock_release(&(ssp)->dep_map);
     181                 :     103979 :         __srcu_read_unlock(ssp, idx);
     182                 :     103506 : }
     183                 :            : 
     184                 :            : /* Used by tracing, cannot be traced and cannot call lockdep. */
     185                 :            : static inline notrace void
     186                 :          0 : srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
     187                 :            : {
     188                 :          0 :         __srcu_read_unlock(ssp, idx);
     189                 :            : }
     190                 :            : 
     191                 :            : /**
     192                 :            :  * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
     193                 :            :  *
     194                 :            :  * Converts the preceding srcu_read_unlock into a two-way memory barrier.
     195                 :            :  *
     196                 :            :  * Call this after srcu_read_unlock, to guarantee that all memory operations
     197                 :            :  * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
     198                 :            :  * the preceding srcu_read_unlock.
     199                 :            :  */
     200                 :            : static inline void smp_mb__after_srcu_read_unlock(void)
     201                 :            : {
     202                 :            :         /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
     203                 :            : }
     204                 :            : 
     205                 :            : #endif