Ingo Molnar | 8446f1d | 2005-09-06 15:16:27 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Detect Soft Lockups |
| 3 | * |
| 4 | * started by Ingo Molnar, (C) 2005, Red Hat |
| 5 | * |
| 6 | * this code detects soft lockups: incidents in where on a CPU |
| 7 | * the kernel does not reschedule for 10 seconds or more. |
| 8 | */ |
| 9 | |
| 10 | #include <linux/mm.h> |
| 11 | #include <linux/cpu.h> |
| 12 | #include <linux/init.h> |
| 13 | #include <linux/delay.h> |
| 14 | #include <linux/kthread.h> |
| 15 | #include <linux/notifier.h> |
| 16 | #include <linux/module.h> |
| 17 | |
| 18 | static DEFINE_SPINLOCK(print_lock); |
| 19 | |
| 20 | static DEFINE_PER_CPU(unsigned long, timestamp) = 0; |
| 21 | static DEFINE_PER_CPU(unsigned long, print_timestamp) = 0; |
| 22 | static DEFINE_PER_CPU(struct task_struct *, watchdog_task); |
| 23 | |
| 24 | static int did_panic = 0; |
| 25 | static int softlock_panic(struct notifier_block *this, unsigned long event, |
| 26 | void *ptr) |
| 27 | { |
| 28 | did_panic = 1; |
| 29 | |
| 30 | return NOTIFY_DONE; |
| 31 | } |
| 32 | |
| 33 | static struct notifier_block panic_block = { |
| 34 | .notifier_call = softlock_panic, |
| 35 | }; |
| 36 | |
| 37 | void touch_softlockup_watchdog(void) |
| 38 | { |
| 39 | per_cpu(timestamp, raw_smp_processor_id()) = jiffies; |
| 40 | } |
| 41 | EXPORT_SYMBOL(touch_softlockup_watchdog); |
| 42 | |
| 43 | /* |
| 44 | * This callback runs from the timer interrupt, and checks |
| 45 | * whether the watchdog thread has hung or not: |
| 46 | */ |
| 47 | void softlockup_tick(struct pt_regs *regs) |
| 48 | { |
| 49 | int this_cpu = smp_processor_id(); |
| 50 | unsigned long timestamp = per_cpu(timestamp, this_cpu); |
| 51 | |
| 52 | if (per_cpu(print_timestamp, this_cpu) == timestamp) |
| 53 | return; |
| 54 | |
| 55 | /* Do not cause a second panic when there already was one */ |
| 56 | if (did_panic) |
| 57 | return; |
| 58 | |
| 59 | if (time_after(jiffies, timestamp + 10*HZ)) { |
| 60 | per_cpu(print_timestamp, this_cpu) = timestamp; |
| 61 | |
| 62 | spin_lock(&print_lock); |
| 63 | printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n", |
| 64 | this_cpu); |
| 65 | show_regs(regs); |
| 66 | spin_unlock(&print_lock); |
| 67 | } |
| 68 | } |
| 69 | |
| 70 | /* |
| 71 | * The watchdog thread - runs every second and touches the timestamp. |
| 72 | */ |
| 73 | static int watchdog(void * __bind_cpu) |
| 74 | { |
| 75 | struct sched_param param = { .sched_priority = 99 }; |
| 76 | int this_cpu = (long) __bind_cpu; |
| 77 | |
| 78 | printk("softlockup thread %d started up.\n", this_cpu); |
| 79 | |
| 80 | sched_setscheduler(current, SCHED_FIFO, ¶m); |
| 81 | current->flags |= PF_NOFREEZE; |
| 82 | |
| 83 | set_current_state(TASK_INTERRUPTIBLE); |
| 84 | |
| 85 | /* |
| 86 | * Run briefly once per second - if this gets delayed for |
| 87 | * more than 10 seconds then the debug-printout triggers |
| 88 | * in softlockup_tick(): |
| 89 | */ |
| 90 | while (!kthread_should_stop()) { |
| 91 | msleep_interruptible(1000); |
| 92 | touch_softlockup_watchdog(); |
| 93 | } |
| 94 | __set_current_state(TASK_RUNNING); |
| 95 | |
| 96 | return 0; |
| 97 | } |
| 98 | |
| 99 | /* |
| 100 | * Create/destroy watchdog threads as CPUs come and go: |
| 101 | */ |
| 102 | static int __devinit |
| 103 | cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) |
| 104 | { |
| 105 | int hotcpu = (unsigned long)hcpu; |
| 106 | struct task_struct *p; |
| 107 | |
| 108 | switch (action) { |
| 109 | case CPU_UP_PREPARE: |
| 110 | BUG_ON(per_cpu(watchdog_task, hotcpu)); |
| 111 | p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); |
| 112 | if (IS_ERR(p)) { |
| 113 | printk("watchdog for %i failed\n", hotcpu); |
| 114 | return NOTIFY_BAD; |
| 115 | } |
| 116 | per_cpu(watchdog_task, hotcpu) = p; |
| 117 | kthread_bind(p, hotcpu); |
| 118 | break; |
| 119 | case CPU_ONLINE: |
| 120 | |
| 121 | wake_up_process(per_cpu(watchdog_task, hotcpu)); |
| 122 | break; |
| 123 | #ifdef CONFIG_HOTPLUG_CPU |
| 124 | case CPU_UP_CANCELED: |
| 125 | /* Unbind so it can run. Fall thru. */ |
| 126 | kthread_bind(per_cpu(watchdog_task, hotcpu), smp_processor_id()); |
| 127 | case CPU_DEAD: |
| 128 | p = per_cpu(watchdog_task, hotcpu); |
| 129 | per_cpu(watchdog_task, hotcpu) = NULL; |
| 130 | kthread_stop(p); |
| 131 | break; |
| 132 | #endif /* CONFIG_HOTPLUG_CPU */ |
| 133 | } |
| 134 | return NOTIFY_OK; |
| 135 | } |
| 136 | |
| 137 | static struct notifier_block __devinitdata cpu_nfb = { |
| 138 | .notifier_call = cpu_callback |
| 139 | }; |
| 140 | |
| 141 | __init void spawn_softlockup_task(void) |
| 142 | { |
| 143 | void *cpu = (void *)(long)smp_processor_id(); |
| 144 | |
| 145 | cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
| 146 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
| 147 | register_cpu_notifier(&cpu_nfb); |
| 148 | |
| 149 | notifier_chain_register(&panic_notifier_list, &panic_block); |
| 150 | } |
| 151 | |