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Linux/lib/nmi_backtrace.c

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

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