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> | |
82a1fcb9 | 11 | #include <linux/nmi.h> |
8446f1d3 IM |
12 | #include <linux/init.h> |
13 | #include <linux/delay.h> | |
83144186 | 14 | #include <linux/freezer.h> |
8446f1d3 IM |
15 | #include <linux/kthread.h> |
16 | #include <linux/notifier.h> | |
17 | #include <linux/module.h> | |
18 | ||
43581a10 IM |
19 | #include <asm/irq_regs.h> |
20 | ||
8446f1d3 IM |
21 | static DEFINE_SPINLOCK(print_lock); |
22 | ||
6687a97d IM |
23 | static DEFINE_PER_CPU(unsigned long, touch_timestamp); |
24 | static DEFINE_PER_CPU(unsigned long, print_timestamp); | |
8446f1d3 IM |
25 | static DEFINE_PER_CPU(struct task_struct *, watchdog_task); |
26 | ||
90739081 IM |
27 | static int __read_mostly did_panic; |
28 | unsigned long __read_mostly softlockup_thresh = 60; | |
6687a97d IM |
29 | |
30 | static int | |
31 | softlock_panic(struct notifier_block *this, unsigned long event, void *ptr) | |
8446f1d3 IM |
32 | { |
33 | did_panic = 1; | |
34 | ||
35 | return NOTIFY_DONE; | |
36 | } | |
37 | ||
38 | static struct notifier_block panic_block = { | |
39 | .notifier_call = softlock_panic, | |
40 | }; | |
41 | ||
966812dc JF |
42 | /* |
43 | * Returns seconds, approximately. We don't need nanosecond | |
44 | * resolution, and we don't need to waste time with a big divide when | |
45 | * 2^30ns == 1.074s. | |
46 | */ | |
a3b13c23 | 47 | static unsigned long get_timestamp(int this_cpu) |
966812dc | 48 | { |
82a1fcb9 | 49 | return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ |
966812dc JF |
50 | } |
51 | ||
9c106c11 | 52 | static void __touch_softlockup_watchdog(void) |
8446f1d3 | 53 | { |
a3b13c23 IM |
54 | int this_cpu = raw_smp_processor_id(); |
55 | ||
56 | __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu); | |
8446f1d3 | 57 | } |
9c106c11 JW |
58 | |
59 | void touch_softlockup_watchdog(void) | |
60 | { | |
61 | __raw_get_cpu_var(touch_timestamp) = 0; | |
62 | } | |
8446f1d3 IM |
63 | EXPORT_SYMBOL(touch_softlockup_watchdog); |
64 | ||
04c9167f JF |
65 | void touch_all_softlockup_watchdogs(void) |
66 | { | |
67 | int cpu; | |
68 | ||
69 | /* Cause each CPU to re-update its timestamp rather than complain */ | |
70 | for_each_online_cpu(cpu) | |
71 | per_cpu(touch_timestamp, cpu) = 0; | |
72 | } | |
73 | EXPORT_SYMBOL(touch_all_softlockup_watchdogs); | |
74 | ||
8446f1d3 IM |
75 | /* |
76 | * This callback runs from the timer interrupt, and checks | |
77 | * whether the watchdog thread has hung or not: | |
78 | */ | |
6687a97d | 79 | void softlockup_tick(void) |
8446f1d3 IM |
80 | { |
81 | int this_cpu = smp_processor_id(); | |
6687a97d | 82 | unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu); |
966812dc | 83 | unsigned long print_timestamp; |
43581a10 | 84 | struct pt_regs *regs = get_irq_regs(); |
966812dc | 85 | unsigned long now; |
8446f1d3 | 86 | |
04c9167f | 87 | if (touch_timestamp == 0) { |
9c106c11 | 88 | __touch_softlockup_watchdog(); |
966812dc | 89 | return; |
04c9167f | 90 | } |
966812dc JF |
91 | |
92 | print_timestamp = per_cpu(print_timestamp, this_cpu); | |
93 | ||
94 | /* report at most once a second */ | |
a115d5ca IM |
95 | if ((print_timestamp >= touch_timestamp && |
96 | print_timestamp < (touch_timestamp + 1)) || | |
97 | did_panic || !per_cpu(watchdog_task, this_cpu)) { | |
8446f1d3 | 98 | return; |
a115d5ca | 99 | } |
8446f1d3 | 100 | |
6687a97d IM |
101 | /* do not print during early bootup: */ |
102 | if (unlikely(system_state != SYSTEM_RUNNING)) { | |
9c106c11 | 103 | __touch_softlockup_watchdog(); |
8446f1d3 | 104 | return; |
6687a97d | 105 | } |
8446f1d3 | 106 | |
a3b13c23 | 107 | now = get_timestamp(this_cpu); |
966812dc | 108 | |
ed50d6cb PZ |
109 | /* Wake up the high-prio watchdog task every second: */ |
110 | if (now > (touch_timestamp + 1)) | |
111 | wake_up_process(per_cpu(watchdog_task, this_cpu)); | |
112 | ||
82a1fcb9 | 113 | /* Warn about unreasonable delays: */ |
c4f3b63f | 114 | if (now <= (touch_timestamp + softlockup_thresh)) |
43581a10 | 115 | return; |
8446f1d3 | 116 | |
43581a10 IM |
117 | per_cpu(print_timestamp, this_cpu) = touch_timestamp; |
118 | ||
119 | spin_lock(&print_lock); | |
c4f3b63f RT |
120 | printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n", |
121 | this_cpu, now - touch_timestamp, | |
ba25f9dc | 122 | current->comm, task_pid_nr(current)); |
43581a10 IM |
123 | if (regs) |
124 | show_regs(regs); | |
125 | else | |
6687a97d | 126 | dump_stack(); |
43581a10 | 127 | spin_unlock(&print_lock); |
8446f1d3 IM |
128 | } |
129 | ||
82a1fcb9 IM |
130 | /* |
131 | * Have a reasonable limit on the number of tasks checked: | |
132 | */ | |
90739081 | 133 | unsigned long __read_mostly sysctl_hung_task_check_count = 1024; |
82a1fcb9 IM |
134 | |
135 | /* | |
136 | * Zero means infinite timeout - no checking done: | |
137 | */ | |
90739081 | 138 | unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120; |
82a1fcb9 | 139 | |
90739081 | 140 | unsigned long __read_mostly sysctl_hung_task_warnings = 10; |
82a1fcb9 IM |
141 | |
142 | /* | |
143 | * Only do the hung-tasks check on one CPU: | |
144 | */ | |
145 | static int check_cpu __read_mostly = -1; | |
146 | ||
147 | static void check_hung_task(struct task_struct *t, unsigned long now) | |
148 | { | |
149 | unsigned long switch_count = t->nvcsw + t->nivcsw; | |
150 | ||
151 | if (t->flags & PF_FROZEN) | |
152 | return; | |
153 | ||
154 | if (switch_count != t->last_switch_count || !t->last_switch_timestamp) { | |
155 | t->last_switch_count = switch_count; | |
156 | t->last_switch_timestamp = now; | |
157 | return; | |
158 | } | |
159 | if ((long)(now - t->last_switch_timestamp) < | |
160 | sysctl_hung_task_timeout_secs) | |
161 | return; | |
162 | if (sysctl_hung_task_warnings < 0) | |
163 | return; | |
164 | sysctl_hung_task_warnings--; | |
165 | ||
166 | /* | |
167 | * Ok, the task did not get scheduled for more than 2 minutes, | |
168 | * complain: | |
169 | */ | |
170 | printk(KERN_ERR "INFO: task %s:%d blocked for more than " | |
171 | "%ld seconds.\n", t->comm, t->pid, | |
172 | sysctl_hung_task_timeout_secs); | |
173 | printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" | |
174 | " disables this message.\n"); | |
175 | sched_show_task(t); | |
176 | __debug_show_held_locks(t); | |
177 | ||
178 | t->last_switch_timestamp = now; | |
179 | touch_nmi_watchdog(); | |
180 | } | |
181 | ||
182 | /* | |
183 | * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for | |
184 | * a really long time (120 seconds). If that happens, print out | |
185 | * a warning. | |
186 | */ | |
187 | static void check_hung_uninterruptible_tasks(int this_cpu) | |
188 | { | |
189 | int max_count = sysctl_hung_task_check_count; | |
190 | unsigned long now = get_timestamp(this_cpu); | |
191 | struct task_struct *g, *t; | |
192 | ||
193 | /* | |
194 | * If the system crashed already then all bets are off, | |
195 | * do not report extra hung tasks: | |
196 | */ | |
197 | if ((tainted & TAINT_DIE) || did_panic) | |
198 | return; | |
199 | ||
200 | read_lock(&tasklist_lock); | |
201 | do_each_thread(g, t) { | |
202 | if (!--max_count) | |
ed50d6cb | 203 | goto unlock; |
82a1fcb9 IM |
204 | if (t->state & TASK_UNINTERRUPTIBLE) |
205 | check_hung_task(t, now); | |
206 | } while_each_thread(g, t); | |
ed50d6cb | 207 | unlock: |
82a1fcb9 IM |
208 | read_unlock(&tasklist_lock); |
209 | } | |
210 | ||
8446f1d3 IM |
211 | /* |
212 | * The watchdog thread - runs every second and touches the timestamp. | |
213 | */ | |
a5f2ce3c | 214 | static int watchdog(void *__bind_cpu) |
8446f1d3 | 215 | { |
02fb6149 | 216 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |
82a1fcb9 | 217 | int this_cpu = (long)__bind_cpu; |
8446f1d3 IM |
218 | |
219 | sched_setscheduler(current, SCHED_FIFO, ¶m); | |
8446f1d3 | 220 | |
966812dc | 221 | /* initialize timestamp */ |
9c106c11 | 222 | __touch_softlockup_watchdog(); |
966812dc | 223 | |
7be2a03e | 224 | set_current_state(TASK_INTERRUPTIBLE); |
8446f1d3 | 225 | /* |
6687a97d | 226 | * Run briefly once per second to reset the softlockup timestamp. |
82a1fcb9 | 227 | * If this gets delayed for more than 60 seconds then the |
6687a97d | 228 | * debug-printout triggers in softlockup_tick(). |
8446f1d3 IM |
229 | */ |
230 | while (!kthread_should_stop()) { | |
9c106c11 | 231 | __touch_softlockup_watchdog(); |
ed50d6cb PZ |
232 | schedule(); |
233 | ||
234 | if (kthread_should_stop()) | |
235 | break; | |
82a1fcb9 | 236 | |
7be2a03e DA |
237 | if (this_cpu == check_cpu) { |
238 | if (sysctl_hung_task_timeout_secs) | |
239 | check_hung_uninterruptible_tasks(this_cpu); | |
240 | } | |
ed50d6cb | 241 | |
7be2a03e | 242 | set_current_state(TASK_INTERRUPTIBLE); |
8446f1d3 | 243 | } |
7be2a03e | 244 | __set_current_state(TASK_RUNNING); |
8446f1d3 IM |
245 | |
246 | return 0; | |
247 | } | |
248 | ||
249 | /* | |
250 | * Create/destroy watchdog threads as CPUs come and go: | |
251 | */ | |
8c78f307 | 252 | static int __cpuinit |
8446f1d3 IM |
253 | cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) |
254 | { | |
255 | int hotcpu = (unsigned long)hcpu; | |
256 | struct task_struct *p; | |
257 | ||
258 | switch (action) { | |
259 | case CPU_UP_PREPARE: | |
8bb78442 | 260 | case CPU_UP_PREPARE_FROZEN: |
8446f1d3 IM |
261 | BUG_ON(per_cpu(watchdog_task, hotcpu)); |
262 | p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); | |
263 | if (IS_ERR(p)) { | |
a5f2ce3c | 264 | printk(KERN_ERR "watchdog for %i failed\n", hotcpu); |
8446f1d3 IM |
265 | return NOTIFY_BAD; |
266 | } | |
a5f2ce3c IM |
267 | per_cpu(touch_timestamp, hotcpu) = 0; |
268 | per_cpu(watchdog_task, hotcpu) = p; | |
8446f1d3 | 269 | kthread_bind(p, hotcpu); |
a5f2ce3c | 270 | break; |
8446f1d3 | 271 | case CPU_ONLINE: |
8bb78442 | 272 | case CPU_ONLINE_FROZEN: |
82a1fcb9 | 273 | check_cpu = any_online_cpu(cpu_online_map); |
8446f1d3 IM |
274 | wake_up_process(per_cpu(watchdog_task, hotcpu)); |
275 | break; | |
276 | #ifdef CONFIG_HOTPLUG_CPU | |
82a1fcb9 IM |
277 | case CPU_DOWN_PREPARE: |
278 | case CPU_DOWN_PREPARE_FROZEN: | |
279 | if (hotcpu == check_cpu) { | |
280 | cpumask_t temp_cpu_online_map = cpu_online_map; | |
281 | ||
282 | cpu_clear(hotcpu, temp_cpu_online_map); | |
283 | check_cpu = any_online_cpu(temp_cpu_online_map); | |
284 | } | |
285 | break; | |
ed50d6cb PZ |
286 | |
287 | case CPU_UP_CANCELED: | |
288 | case CPU_UP_CANCELED_FROZEN: | |
289 | if (!per_cpu(watchdog_task, hotcpu)) | |
290 | break; | |
291 | /* Unbind so it can run. Fall thru. */ | |
292 | kthread_bind(per_cpu(watchdog_task, hotcpu), | |
293 | any_online_cpu(cpu_online_map)); | |
8446f1d3 | 294 | case CPU_DEAD: |
8bb78442 | 295 | case CPU_DEAD_FROZEN: |
8446f1d3 IM |
296 | p = per_cpu(watchdog_task, hotcpu); |
297 | per_cpu(watchdog_task, hotcpu) = NULL; | |
298 | kthread_stop(p); | |
299 | break; | |
300 | #endif /* CONFIG_HOTPLUG_CPU */ | |
a5f2ce3c | 301 | } |
8446f1d3 IM |
302 | return NOTIFY_OK; |
303 | } | |
304 | ||
8c78f307 | 305 | static struct notifier_block __cpuinitdata cpu_nfb = { |
8446f1d3 IM |
306 | .notifier_call = cpu_callback |
307 | }; | |
308 | ||
309 | __init void spawn_softlockup_task(void) | |
310 | { | |
311 | void *cpu = (void *)(long)smp_processor_id(); | |
07dccf33 | 312 | int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
8446f1d3 | 313 | |
07dccf33 | 314 | BUG_ON(err == NOTIFY_BAD); |
8446f1d3 IM |
315 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
316 | register_cpu_notifier(&cpu_nfb); | |
317 | ||
e041c683 | 318 | atomic_notifier_chain_register(&panic_notifier_list, &panic_block); |
8446f1d3 | 319 | } |