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 #include <linux/sched/debug.h> 21 22 #ifdef arch_trigger_cpumask_backtrace 23 /* For reliability, we're prepared to waste bits here. */ 24 static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; 25 26 /* "in progress" flag of arch_trigger_cpumask_backtrace */ 27 static unsigned long backtrace_flag; 28 29 /* 30 * When raise() is called it will be passed a pointer to the 31 * backtrace_mask. Architectures that call nmi_cpu_backtrace() 32 * directly from their raise() functions may rely on the mask 33 * they are passed being updated as a side effect of this call. 34 */ 35 void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, 36 bool exclude_self, 37 void (*raise)(cpumask_t *mask)) 38 { 39 int i, this_cpu = get_cpu(); 40 41 if (test_and_set_bit(0, &backtrace_flag)) { 42 /* 43 * If there is already a trigger_all_cpu_backtrace() in progress 44 * (backtrace_flag == 1), don't output double cpu dump infos. 45 */ 46 put_cpu(); 47 return; 48 } 49 50 cpumask_copy(to_cpumask(backtrace_mask), mask); 51 if (exclude_self) 52 cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask)); 53 54 /* 55 * Don't try to send an NMI to this cpu; it may work on some 56 * architectures, but on others it may not, and we'll get 57 * information at least as useful just by doing a dump_stack() here. 58 * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit. 59 */ 60 if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask))) 61 nmi_cpu_backtrace(NULL); 62 63 if (!cpumask_empty(to_cpumask(backtrace_mask))) { 64 pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n", 65 this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask)); 66 raise(to_cpumask(backtrace_mask)); 67 } 68 69 /* Wait for up to 10 seconds for all CPUs to do the backtrace */ 70 for (i = 0; i < 10 * 1000; i++) { 71 if (cpumask_empty(to_cpumask(backtrace_mask))) 72 break; 73 mdelay(1); 74 touch_softlockup_watchdog(); 75 } 76 77 /* 78 * Force flush any remote buffers that might be stuck in IRQ context 79 * and therefore could not run their irq_work. 80 */ 81 printk_safe_flush(); 82 83 clear_bit_unlock(0, &backtrace_flag); 84 put_cpu(); 85 } 86 87 bool nmi_cpu_backtrace(struct pt_regs *regs) 88 { 89 static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED; 90 int cpu = smp_processor_id(); 91 92 if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { 93 arch_spin_lock(&lock); 94 if (regs && cpu_in_idle(instruction_pointer(regs))) { 95 pr_warn("NMI backtrace for cpu %d skipped: idling at pc %#lx\n", 96 cpu, instruction_pointer(regs)); 97 } else { 98 pr_warn("NMI backtrace for cpu %d\n", cpu); 99 if (regs) 100 show_regs(regs); 101 else 102 dump_stack(); 103 } 104 arch_spin_unlock(&lock); 105 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask)); 106 return true; 107 } 108 109 return false; 110 } 111 NOKPROBE_SYMBOL(nmi_cpu_backtrace); 112 #endif 113