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