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