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 void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, 37 bool exclude_self, 38 void (*raise)(cpumask_t *mask)) 39 { 40 int i, this_cpu = get_cpu(); 41 42 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 put_cpu(); 48 return; 49 } 50 51 cpumask_copy(to_cpumask(backtrace_mask), mask); 52 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 if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask))) 62 nmi_cpu_backtrace(NULL); 63 64 if (!cpumask_empty(to_cpumask(backtrace_mask))) { 65 pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n", 66 this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask)); 67 raise(to_cpumask(backtrace_mask)); 68 } 69 70 /* Wait for up to 10 seconds for all CPUs to do the backtrace */ 71 for (i = 0; i < 10 * 1000; i++) { 72 if (cpumask_empty(to_cpumask(backtrace_mask))) 73 break; 74 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 printk_safe_flush(); 83 84 clear_bit_unlock(0, &backtrace_flag); 85 put_cpu(); 86 } 87 88 // Dump stacks even for idle CPUs. 89 static bool backtrace_idle; 90 module_param(backtrace_idle, bool, 0644); 91 92 bool nmi_cpu_backtrace(struct pt_regs *regs) 93 { 94 int cpu = smp_processor_id(); 95 96 if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { 97 if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) { 98 pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n", 99 cpu, (void *)instruction_pointer(regs)); 100 } else { 101 pr_warn("NMI backtrace for cpu %d\n", cpu); 102 if (regs) 103 show_regs(regs); 104 else 105 dump_stack(); 106 } 107 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask)); 108 return true; 109 } 110 111 return false; 112 } 113 NOKPROBE_SYMBOL(nmi_cpu_backtrace); 114 #endif 115