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Commit | Line | Data |
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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> | |
83144186 | 13 | #include <linux/freezer.h> |
8446f1d3 IM |
14 | #include <linux/kthread.h> |
15 | #include <linux/notifier.h> | |
16 | #include <linux/module.h> | |
17 | ||
43581a10 IM |
18 | #include <asm/irq_regs.h> |
19 | ||
8446f1d3 IM |
20 | static DEFINE_SPINLOCK(print_lock); |
21 | ||
6687a97d IM |
22 | static DEFINE_PER_CPU(unsigned long, touch_timestamp); |
23 | static DEFINE_PER_CPU(unsigned long, print_timestamp); | |
8446f1d3 IM |
24 | static DEFINE_PER_CPU(struct task_struct *, watchdog_task); |
25 | ||
a5f2ce3c | 26 | static int did_panic; |
c4f3b63f | 27 | int softlockup_thresh = 10; |
6687a97d IM |
28 | |
29 | static int | |
30 | softlock_panic(struct notifier_block *this, unsigned long event, void *ptr) | |
8446f1d3 IM |
31 | { |
32 | did_panic = 1; | |
33 | ||
34 | return NOTIFY_DONE; | |
35 | } | |
36 | ||
37 | static struct notifier_block panic_block = { | |
38 | .notifier_call = softlock_panic, | |
39 | }; | |
40 | ||
966812dc JF |
41 | /* |
42 | * Returns seconds, approximately. We don't need nanosecond | |
43 | * resolution, and we don't need to waste time with a big divide when | |
44 | * 2^30ns == 1.074s. | |
45 | */ | |
a3b13c23 | 46 | static unsigned long get_timestamp(int this_cpu) |
966812dc | 47 | { |
a3b13c23 | 48 | return cpu_clock(this_cpu) >> 30; /* 2^30 ~= 10^9 */ |
966812dc JF |
49 | } |
50 | ||
8446f1d3 IM |
51 | void touch_softlockup_watchdog(void) |
52 | { | |
a3b13c23 IM |
53 | int this_cpu = raw_smp_processor_id(); |
54 | ||
55 | __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu); | |
8446f1d3 IM |
56 | } |
57 | EXPORT_SYMBOL(touch_softlockup_watchdog); | |
58 | ||
04c9167f JF |
59 | void touch_all_softlockup_watchdogs(void) |
60 | { | |
61 | int cpu; | |
62 | ||
63 | /* Cause each CPU to re-update its timestamp rather than complain */ | |
64 | for_each_online_cpu(cpu) | |
65 | per_cpu(touch_timestamp, cpu) = 0; | |
66 | } | |
67 | EXPORT_SYMBOL(touch_all_softlockup_watchdogs); | |
68 | ||
8446f1d3 IM |
69 | /* |
70 | * This callback runs from the timer interrupt, and checks | |
71 | * whether the watchdog thread has hung or not: | |
72 | */ | |
6687a97d | 73 | void softlockup_tick(void) |
8446f1d3 IM |
74 | { |
75 | int this_cpu = smp_processor_id(); | |
6687a97d | 76 | unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu); |
966812dc | 77 | unsigned long print_timestamp; |
43581a10 | 78 | struct pt_regs *regs = get_irq_regs(); |
966812dc | 79 | unsigned long now; |
8446f1d3 | 80 | |
04c9167f JF |
81 | if (touch_timestamp == 0) { |
82 | touch_softlockup_watchdog(); | |
966812dc | 83 | return; |
04c9167f | 84 | } |
966812dc JF |
85 | |
86 | print_timestamp = per_cpu(print_timestamp, this_cpu); | |
87 | ||
88 | /* report at most once a second */ | |
a115d5ca IM |
89 | if ((print_timestamp >= touch_timestamp && |
90 | print_timestamp < (touch_timestamp + 1)) || | |
91 | did_panic || !per_cpu(watchdog_task, this_cpu)) { | |
8446f1d3 | 92 | return; |
a115d5ca | 93 | } |
8446f1d3 | 94 | |
6687a97d IM |
95 | /* do not print during early bootup: */ |
96 | if (unlikely(system_state != SYSTEM_RUNNING)) { | |
97 | touch_softlockup_watchdog(); | |
8446f1d3 | 98 | return; |
6687a97d | 99 | } |
8446f1d3 | 100 | |
a3b13c23 | 101 | now = get_timestamp(this_cpu); |
966812dc | 102 | |
6687a97d | 103 | /* Wake up the high-prio watchdog task every second: */ |
966812dc | 104 | if (now > (touch_timestamp + 1)) |
6687a97d IM |
105 | wake_up_process(per_cpu(watchdog_task, this_cpu)); |
106 | ||
107 | /* Warn about unreasonable 10+ seconds delays: */ | |
c4f3b63f | 108 | if (now <= (touch_timestamp + softlockup_thresh)) |
43581a10 | 109 | return; |
8446f1d3 | 110 | |
43581a10 IM |
111 | per_cpu(print_timestamp, this_cpu) = touch_timestamp; |
112 | ||
113 | spin_lock(&print_lock); | |
c4f3b63f RT |
114 | printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n", |
115 | this_cpu, now - touch_timestamp, | |
ba25f9dc | 116 | current->comm, task_pid_nr(current)); |
43581a10 IM |
117 | if (regs) |
118 | show_regs(regs); | |
119 | else | |
6687a97d | 120 | dump_stack(); |
43581a10 | 121 | spin_unlock(&print_lock); |
8446f1d3 IM |
122 | } |
123 | ||
124 | /* | |
125 | * The watchdog thread - runs every second and touches the timestamp. | |
126 | */ | |
a5f2ce3c | 127 | static int watchdog(void *__bind_cpu) |
8446f1d3 | 128 | { |
02fb6149 | 129 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |
8446f1d3 IM |
130 | |
131 | sched_setscheduler(current, SCHED_FIFO, ¶m); | |
8446f1d3 | 132 | |
966812dc JF |
133 | /* initialize timestamp */ |
134 | touch_softlockup_watchdog(); | |
135 | ||
8446f1d3 | 136 | /* |
6687a97d IM |
137 | * Run briefly once per second to reset the softlockup timestamp. |
138 | * If this gets delayed for more than 10 seconds then the | |
139 | * debug-printout triggers in softlockup_tick(). | |
8446f1d3 IM |
140 | */ |
141 | while (!kthread_should_stop()) { | |
6687a97d | 142 | set_current_state(TASK_INTERRUPTIBLE); |
8446f1d3 | 143 | touch_softlockup_watchdog(); |
6687a97d | 144 | schedule(); |
8446f1d3 | 145 | } |
8446f1d3 IM |
146 | |
147 | return 0; | |
148 | } | |
149 | ||
150 | /* | |
151 | * Create/destroy watchdog threads as CPUs come and go: | |
152 | */ | |
8c78f307 | 153 | static int __cpuinit |
8446f1d3 IM |
154 | cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) |
155 | { | |
156 | int hotcpu = (unsigned long)hcpu; | |
157 | struct task_struct *p; | |
158 | ||
159 | switch (action) { | |
160 | case CPU_UP_PREPARE: | |
8bb78442 | 161 | case CPU_UP_PREPARE_FROZEN: |
8446f1d3 IM |
162 | BUG_ON(per_cpu(watchdog_task, hotcpu)); |
163 | p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); | |
164 | if (IS_ERR(p)) { | |
a5f2ce3c | 165 | printk(KERN_ERR "watchdog for %i failed\n", hotcpu); |
8446f1d3 IM |
166 | return NOTIFY_BAD; |
167 | } | |
a5f2ce3c IM |
168 | per_cpu(touch_timestamp, hotcpu) = 0; |
169 | per_cpu(watchdog_task, hotcpu) = p; | |
8446f1d3 | 170 | kthread_bind(p, hotcpu); |
a5f2ce3c | 171 | break; |
8446f1d3 | 172 | case CPU_ONLINE: |
8bb78442 | 173 | case CPU_ONLINE_FROZEN: |
8446f1d3 IM |
174 | wake_up_process(per_cpu(watchdog_task, hotcpu)); |
175 | break; | |
176 | #ifdef CONFIG_HOTPLUG_CPU | |
177 | case CPU_UP_CANCELED: | |
8bb78442 | 178 | case CPU_UP_CANCELED_FROZEN: |
fc75cdfa HC |
179 | if (!per_cpu(watchdog_task, hotcpu)) |
180 | break; | |
8446f1d3 | 181 | /* Unbind so it can run. Fall thru. */ |
a4c4af7c HC |
182 | kthread_bind(per_cpu(watchdog_task, hotcpu), |
183 | any_online_cpu(cpu_online_map)); | |
8446f1d3 | 184 | case CPU_DEAD: |
8bb78442 | 185 | case CPU_DEAD_FROZEN: |
8446f1d3 IM |
186 | p = per_cpu(watchdog_task, hotcpu); |
187 | per_cpu(watchdog_task, hotcpu) = NULL; | |
188 | kthread_stop(p); | |
189 | break; | |
190 | #endif /* CONFIG_HOTPLUG_CPU */ | |
a5f2ce3c | 191 | } |
8446f1d3 IM |
192 | return NOTIFY_OK; |
193 | } | |
194 | ||
8c78f307 | 195 | static struct notifier_block __cpuinitdata cpu_nfb = { |
8446f1d3 IM |
196 | .notifier_call = cpu_callback |
197 | }; | |
198 | ||
199 | __init void spawn_softlockup_task(void) | |
200 | { | |
201 | void *cpu = (void *)(long)smp_processor_id(); | |
07dccf33 | 202 | int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
8446f1d3 | 203 | |
07dccf33 | 204 | BUG_ON(err == NOTIFY_BAD); |
8446f1d3 IM |
205 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
206 | register_cpu_notifier(&cpu_nfb); | |
207 | ||
e041c683 | 208 | atomic_notifier_chain_register(&panic_notifier_list, &panic_block); |
8446f1d3 | 209 | } |