LCOV - code coverage report
Current view: top level - lib - nmi_backtrace.c (source / functions) Hit Total Coverage
Test: gcov_data_raspi2_real_modules_combined.info Lines: 0 26 0.0 %
Date: 2020-09-30 20:25:40 Functions: 0 2 0.0 %
Branches: 0 20 0.0 %

           Branch data     Line data    Source code
       1                 :            : // SPDX-License-Identifier: GPL-2.0
       2                 :            : /*
       3                 :            :  *  NMI backtrace support
       4                 :            :  *
       5                 :            :  * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
       6                 :            :  * with the following header:
       7                 :            :  *
       8                 :            :  *  HW NMI watchdog support
       9                 :            :  *
      10                 :            :  *  started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
      11                 :            :  *
      12                 :            :  *  Arch specific calls to support NMI watchdog
      13                 :            :  *
      14                 :            :  *  Bits copied from original nmi.c file
      15                 :            :  */
      16                 :            : #include <linux/cpumask.h>
      17                 :            : #include <linux/delay.h>
      18                 :            : #include <linux/kprobes.h>
      19                 :            : #include <linux/nmi.h>
      20                 :            : #include <linux/cpu.h>
      21                 :            : #include <linux/sched/debug.h>
      22                 :            : 
      23                 :            : #ifdef arch_trigger_cpumask_backtrace
      24                 :            : /* For reliability, we're prepared to waste bits here. */
      25                 :            : static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
      26                 :            : 
      27                 :            : /* "in progress" flag of arch_trigger_cpumask_backtrace */
      28                 :            : static unsigned long backtrace_flag;
      29                 :            : 
      30                 :            : /*
      31                 :            :  * When raise() is called it will be passed a pointer to the
      32                 :            :  * backtrace_mask. Architectures that call nmi_cpu_backtrace()
      33                 :            :  * directly from their raise() functions may rely on the mask
      34                 :            :  * they are passed being updated as a side effect of this call.
      35                 :            :  */
      36                 :          0 : void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
      37                 :            :                                    bool exclude_self,
      38                 :            :                                    void (*raise)(cpumask_t *mask))
      39                 :            : {
      40                 :          0 :         int i, this_cpu = get_cpu();
      41                 :            : 
      42         [ #  # ]:          0 :         if (test_and_set_bit(0, &backtrace_flag)) {
      43                 :            :                 /*
      44                 :            :                  * If there is already a trigger_all_cpu_backtrace() in progress
      45                 :            :                  * (backtrace_flag == 1), don't output double cpu dump infos.
      46                 :            :                  */
      47                 :          0 :                 put_cpu();
      48                 :          0 :                 return;
      49                 :            :         }
      50                 :            : 
      51                 :            :         cpumask_copy(to_cpumask(backtrace_mask), mask);
      52         [ #  # ]:          0 :         if (exclude_self)
      53                 :            :                 cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
      54                 :            : 
      55                 :            :         /*
      56                 :            :          * Don't try to send an NMI to this cpu; it may work on some
      57                 :            :          * architectures, but on others it may not, and we'll get
      58                 :            :          * information at least as useful just by doing a dump_stack() here.
      59                 :            :          * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
      60                 :            :          */
      61         [ #  # ]:          0 :         if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
      62                 :          0 :                 nmi_cpu_backtrace(NULL);
      63                 :            : 
      64         [ #  # ]:          0 :         if (!cpumask_empty(to_cpumask(backtrace_mask))) {
      65                 :          0 :                 pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
      66                 :            :                         this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
      67                 :          0 :                 raise(to_cpumask(backtrace_mask));
      68                 :            :         }
      69                 :            : 
      70                 :            :         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
      71         [ #  # ]:          0 :         for (i = 0; i < 10 * 1000; i++) {
      72         [ #  # ]:          0 :                 if (cpumask_empty(to_cpumask(backtrace_mask)))
      73                 :            :                         break;
      74                 :          0 :                 mdelay(1);
      75                 :            :                 touch_softlockup_watchdog();
      76                 :            :         }
      77                 :            : 
      78                 :            :         /*
      79                 :            :          * Force flush any remote buffers that might be stuck in IRQ context
      80                 :            :          * and therefore could not run their irq_work.
      81                 :            :          */
      82                 :          0 :         printk_safe_flush();
      83                 :            : 
      84                 :          0 :         clear_bit_unlock(0, &backtrace_flag);
      85                 :          0 :         put_cpu();
      86                 :            : }
      87                 :            : 
      88                 :          0 : bool nmi_cpu_backtrace(struct pt_regs *regs)
      89                 :            : {
      90                 :            :         int cpu = smp_processor_id();
      91                 :            : 
      92         [ #  # ]:          0 :         if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
      93   [ #  #  #  # ]:          0 :                 if (regs && cpu_in_idle(instruction_pointer(regs))) {
      94                 :          0 :                         pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
      95                 :            :                                 cpu, (void *)instruction_pointer(regs));
      96                 :            :                 } else {
      97                 :          0 :                         pr_warn("NMI backtrace for cpu %d\n", cpu);
      98         [ #  # ]:          0 :                         if (regs)
      99                 :          0 :                                 show_regs(regs);
     100                 :            :                         else
     101                 :          0 :                                 dump_stack();
     102                 :            :                 }
     103                 :            :                 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
     104                 :          0 :                 return true;
     105                 :            :         }
     106                 :            : 
     107                 :            :         return false;
     108                 :            : }
     109                 :            : NOKPROBE_SYMBOL(nmi_cpu_backtrace);
     110                 :            : #endif

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