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8446f1d3 IM |
1 | /* |
2 | * Detect Soft Lockups | |
3 | * | |
6687a97d | 4 | * started by Ingo Molnar, Copyright (C) 2005, 2006 Red Hat, Inc. |
8446f1d3 IM |
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 | */ | |
8446f1d3 IM |
9 | #include <linux/mm.h> |
10 | #include <linux/cpu.h> | |
11 | #include <linux/init.h> | |
12 | #include <linux/delay.h> | |
13 | #include <linux/kthread.h> | |
14 | #include <linux/notifier.h> | |
15 | #include <linux/module.h> | |
16 | ||
17 | static DEFINE_SPINLOCK(print_lock); | |
18 | ||
6687a97d IM |
19 | static DEFINE_PER_CPU(unsigned long, touch_timestamp); |
20 | static DEFINE_PER_CPU(unsigned long, print_timestamp); | |
8446f1d3 IM |
21 | static DEFINE_PER_CPU(struct task_struct *, watchdog_task); |
22 | ||
23 | static int did_panic = 0; | |
6687a97d IM |
24 | |
25 | static int | |
26 | softlock_panic(struct notifier_block *this, unsigned long event, void *ptr) | |
8446f1d3 IM |
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 | { | |
bfe5d834 | 39 | __raw_get_cpu_var(touch_timestamp) = jiffies; |
8446f1d3 IM |
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 | */ | |
6687a97d | 47 | void softlockup_tick(void) |
8446f1d3 IM |
48 | { |
49 | int this_cpu = smp_processor_id(); | |
6687a97d | 50 | unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu); |
8446f1d3 | 51 | |
6687a97d IM |
52 | /* prevent double reports: */ |
53 | if (per_cpu(print_timestamp, this_cpu) == touch_timestamp || | |
54 | did_panic || | |
55 | !per_cpu(watchdog_task, this_cpu)) | |
8446f1d3 IM |
56 | return; |
57 | ||
6687a97d IM |
58 | /* do not print during early bootup: */ |
59 | if (unlikely(system_state != SYSTEM_RUNNING)) { | |
60 | touch_softlockup_watchdog(); | |
8446f1d3 | 61 | return; |
6687a97d | 62 | } |
8446f1d3 | 63 | |
6687a97d IM |
64 | /* Wake up the high-prio watchdog task every second: */ |
65 | if (time_after(jiffies, touch_timestamp + HZ)) | |
66 | wake_up_process(per_cpu(watchdog_task, this_cpu)); | |
67 | ||
68 | /* Warn about unreasonable 10+ seconds delays: */ | |
69 | if (time_after(jiffies, touch_timestamp + 10*HZ)) { | |
70 | per_cpu(print_timestamp, this_cpu) = touch_timestamp; | |
8446f1d3 IM |
71 | |
72 | spin_lock(&print_lock); | |
73 | printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n", | |
74 | this_cpu); | |
6687a97d | 75 | dump_stack(); |
8446f1d3 IM |
76 | spin_unlock(&print_lock); |
77 | } | |
78 | } | |
79 | ||
80 | /* | |
81 | * The watchdog thread - runs every second and touches the timestamp. | |
82 | */ | |
83 | static int watchdog(void * __bind_cpu) | |
84 | { | |
02fb6149 | 85 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |
8446f1d3 IM |
86 | |
87 | sched_setscheduler(current, SCHED_FIFO, ¶m); | |
88 | current->flags |= PF_NOFREEZE; | |
89 | ||
8446f1d3 | 90 | /* |
6687a97d IM |
91 | * Run briefly once per second to reset the softlockup timestamp. |
92 | * If this gets delayed for more than 10 seconds then the | |
93 | * debug-printout triggers in softlockup_tick(). | |
8446f1d3 IM |
94 | */ |
95 | while (!kthread_should_stop()) { | |
6687a97d | 96 | set_current_state(TASK_INTERRUPTIBLE); |
8446f1d3 | 97 | touch_softlockup_watchdog(); |
6687a97d | 98 | schedule(); |
8446f1d3 | 99 | } |
8446f1d3 IM |
100 | |
101 | return 0; | |
102 | } | |
103 | ||
104 | /* | |
105 | * Create/destroy watchdog threads as CPUs come and go: | |
106 | */ | |
8c78f307 | 107 | static int __cpuinit |
8446f1d3 IM |
108 | cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) |
109 | { | |
110 | int hotcpu = (unsigned long)hcpu; | |
111 | struct task_struct *p; | |
112 | ||
113 | switch (action) { | |
114 | case CPU_UP_PREPARE: | |
115 | BUG_ON(per_cpu(watchdog_task, hotcpu)); | |
116 | p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); | |
117 | if (IS_ERR(p)) { | |
118 | printk("watchdog for %i failed\n", hotcpu); | |
119 | return NOTIFY_BAD; | |
120 | } | |
185ae6d7 | 121 | per_cpu(touch_timestamp, hotcpu) = jiffies; |
8446f1d3 IM |
122 | per_cpu(watchdog_task, hotcpu) = p; |
123 | kthread_bind(p, hotcpu); | |
124 | break; | |
125 | case CPU_ONLINE: | |
8446f1d3 IM |
126 | wake_up_process(per_cpu(watchdog_task, hotcpu)); |
127 | break; | |
128 | #ifdef CONFIG_HOTPLUG_CPU | |
129 | case CPU_UP_CANCELED: | |
fc75cdfa HC |
130 | if (!per_cpu(watchdog_task, hotcpu)) |
131 | break; | |
8446f1d3 | 132 | /* Unbind so it can run. Fall thru. */ |
a4c4af7c HC |
133 | kthread_bind(per_cpu(watchdog_task, hotcpu), |
134 | any_online_cpu(cpu_online_map)); | |
8446f1d3 IM |
135 | case CPU_DEAD: |
136 | p = per_cpu(watchdog_task, hotcpu); | |
137 | per_cpu(watchdog_task, hotcpu) = NULL; | |
138 | kthread_stop(p); | |
139 | break; | |
140 | #endif /* CONFIG_HOTPLUG_CPU */ | |
141 | } | |
142 | return NOTIFY_OK; | |
143 | } | |
144 | ||
8c78f307 | 145 | static struct notifier_block __cpuinitdata cpu_nfb = { |
8446f1d3 IM |
146 | .notifier_call = cpu_callback |
147 | }; | |
148 | ||
149 | __init void spawn_softlockup_task(void) | |
150 | { | |
151 | void *cpu = (void *)(long)smp_processor_id(); | |
07dccf33 | 152 | int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
8446f1d3 | 153 | |
07dccf33 | 154 | BUG_ON(err == NOTIFY_BAD); |
8446f1d3 IM |
155 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
156 | register_cpu_notifier(&cpu_nfb); | |
157 | ||
e041c683 | 158 | atomic_notifier_chain_register(&panic_notifier_list, &panic_block); |
8446f1d3 | 159 | } |