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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> | |
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 | 15 | #include <linux/kthread.h> |
8d5be7f4 | 16 | #include <linux/lockdep.h> |
8446f1d3 IM |
17 | #include <linux/notifier.h> |
18 | #include <linux/module.h> | |
19 | ||
43581a10 IM |
20 | #include <asm/irq_regs.h> |
21 | ||
8446f1d3 IM |
22 | static DEFINE_SPINLOCK(print_lock); |
23 | ||
6687a97d IM |
24 | static DEFINE_PER_CPU(unsigned long, touch_timestamp); |
25 | static DEFINE_PER_CPU(unsigned long, print_timestamp); | |
8446f1d3 IM |
26 | static DEFINE_PER_CPU(struct task_struct *, watchdog_task); |
27 | ||
90739081 | 28 | static int __read_mostly did_panic; |
9383d967 | 29 | int __read_mostly softlockup_thresh = 60; |
6687a97d | 30 | |
9c44bc03 IM |
31 | /* |
32 | * Should we panic (and reboot, if panic_timeout= is set) when a | |
33 | * soft-lockup occurs: | |
34 | */ | |
35 | unsigned int __read_mostly softlockup_panic = | |
36 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
37 | ||
38 | static int __init softlockup_panic_setup(char *str) | |
39 | { | |
40 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
41 | ||
42 | return 1; | |
43 | } | |
44 | __setup("softlockup_panic=", softlockup_panic_setup); | |
45 | ||
6687a97d IM |
46 | static int |
47 | softlock_panic(struct notifier_block *this, unsigned long event, void *ptr) | |
8446f1d3 IM |
48 | { |
49 | did_panic = 1; | |
50 | ||
51 | return NOTIFY_DONE; | |
52 | } | |
53 | ||
54 | static struct notifier_block panic_block = { | |
55 | .notifier_call = softlock_panic, | |
56 | }; | |
57 | ||
966812dc JF |
58 | /* |
59 | * Returns seconds, approximately. We don't need nanosecond | |
60 | * resolution, and we don't need to waste time with a big divide when | |
61 | * 2^30ns == 1.074s. | |
62 | */ | |
a3b13c23 | 63 | static unsigned long get_timestamp(int this_cpu) |
966812dc | 64 | { |
82a1fcb9 | 65 | return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ |
966812dc JF |
66 | } |
67 | ||
8c2238ea | 68 | static void __touch_softlockup_watchdog(void) |
8446f1d3 | 69 | { |
a3b13c23 IM |
70 | int this_cpu = raw_smp_processor_id(); |
71 | ||
72 | __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu); | |
8446f1d3 | 73 | } |
8c2238ea JW |
74 | |
75 | void touch_softlockup_watchdog(void) | |
76 | { | |
77 | __raw_get_cpu_var(touch_timestamp) = 0; | |
78 | } | |
8446f1d3 IM |
79 | EXPORT_SYMBOL(touch_softlockup_watchdog); |
80 | ||
04c9167f JF |
81 | void touch_all_softlockup_watchdogs(void) |
82 | { | |
83 | int cpu; | |
84 | ||
85 | /* Cause each CPU to re-update its timestamp rather than complain */ | |
86 | for_each_online_cpu(cpu) | |
87 | per_cpu(touch_timestamp, cpu) = 0; | |
88 | } | |
89 | EXPORT_SYMBOL(touch_all_softlockup_watchdogs); | |
90 | ||
8446f1d3 IM |
91 | /* |
92 | * This callback runs from the timer interrupt, and checks | |
93 | * whether the watchdog thread has hung or not: | |
94 | */ | |
6687a97d | 95 | void softlockup_tick(void) |
8446f1d3 IM |
96 | { |
97 | int this_cpu = smp_processor_id(); | |
6687a97d | 98 | unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu); |
966812dc | 99 | unsigned long print_timestamp; |
43581a10 | 100 | struct pt_regs *regs = get_irq_regs(); |
966812dc | 101 | unsigned long now; |
8446f1d3 | 102 | |
9383d967 DS |
103 | /* Is detection switched off? */ |
104 | if (!per_cpu(watchdog_task, this_cpu) || softlockup_thresh <= 0) { | |
105 | /* Be sure we don't false trigger if switched back on */ | |
106 | if (touch_timestamp) | |
107 | per_cpu(touch_timestamp, this_cpu) = 0; | |
108 | return; | |
109 | } | |
110 | ||
04c9167f | 111 | if (touch_timestamp == 0) { |
8c2238ea | 112 | __touch_softlockup_watchdog(); |
966812dc | 113 | return; |
04c9167f | 114 | } |
966812dc JF |
115 | |
116 | print_timestamp = per_cpu(print_timestamp, this_cpu); | |
117 | ||
118 | /* report at most once a second */ | |
a115d5ca IM |
119 | if ((print_timestamp >= touch_timestamp && |
120 | print_timestamp < (touch_timestamp + 1)) || | |
9383d967 | 121 | did_panic) { |
8446f1d3 | 122 | return; |
a115d5ca | 123 | } |
8446f1d3 | 124 | |
6687a97d IM |
125 | /* do not print during early bootup: */ |
126 | if (unlikely(system_state != SYSTEM_RUNNING)) { | |
8c2238ea | 127 | __touch_softlockup_watchdog(); |
8446f1d3 | 128 | return; |
6687a97d | 129 | } |
8446f1d3 | 130 | |
a3b13c23 | 131 | now = get_timestamp(this_cpu); |
966812dc | 132 | |
dd7a1e56 JW |
133 | /* |
134 | * Wake up the high-prio watchdog task twice per | |
135 | * threshold timespan. | |
136 | */ | |
137 | if (now > touch_timestamp + softlockup_thresh/2) | |
ed50d6cb PZ |
138 | wake_up_process(per_cpu(watchdog_task, this_cpu)); |
139 | ||
82a1fcb9 | 140 | /* Warn about unreasonable delays: */ |
c4f3b63f | 141 | if (now <= (touch_timestamp + softlockup_thresh)) |
43581a10 | 142 | return; |
8446f1d3 | 143 | |
43581a10 IM |
144 | per_cpu(print_timestamp, this_cpu) = touch_timestamp; |
145 | ||
146 | spin_lock(&print_lock); | |
c4f3b63f RT |
147 | printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n", |
148 | this_cpu, now - touch_timestamp, | |
ba25f9dc | 149 | current->comm, task_pid_nr(current)); |
688c9175 | 150 | print_modules(); |
8d5be7f4 | 151 | print_irqtrace_events(current); |
43581a10 IM |
152 | if (regs) |
153 | show_regs(regs); | |
154 | else | |
6687a97d | 155 | dump_stack(); |
43581a10 | 156 | spin_unlock(&print_lock); |
9c44bc03 IM |
157 | |
158 | if (softlockup_panic) | |
159 | panic("softlockup: hung tasks"); | |
8446f1d3 IM |
160 | } |
161 | ||
82a1fcb9 IM |
162 | /* |
163 | * Have a reasonable limit on the number of tasks checked: | |
164 | */ | |
90739081 | 165 | unsigned long __read_mostly sysctl_hung_task_check_count = 1024; |
82a1fcb9 IM |
166 | |
167 | /* | |
168 | * Zero means infinite timeout - no checking done: | |
169 | */ | |
90739081 | 170 | unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120; |
82a1fcb9 | 171 | |
90739081 | 172 | unsigned long __read_mostly sysctl_hung_task_warnings = 10; |
82a1fcb9 IM |
173 | |
174 | /* | |
175 | * Only do the hung-tasks check on one CPU: | |
176 | */ | |
177 | static int check_cpu __read_mostly = -1; | |
178 | ||
179 | static void check_hung_task(struct task_struct *t, unsigned long now) | |
180 | { | |
181 | unsigned long switch_count = t->nvcsw + t->nivcsw; | |
182 | ||
183 | if (t->flags & PF_FROZEN) | |
184 | return; | |
185 | ||
186 | if (switch_count != t->last_switch_count || !t->last_switch_timestamp) { | |
187 | t->last_switch_count = switch_count; | |
188 | t->last_switch_timestamp = now; | |
189 | return; | |
190 | } | |
191 | if ((long)(now - t->last_switch_timestamp) < | |
192 | sysctl_hung_task_timeout_secs) | |
193 | return; | |
194 | if (sysctl_hung_task_warnings < 0) | |
195 | return; | |
196 | sysctl_hung_task_warnings--; | |
197 | ||
198 | /* | |
199 | * Ok, the task did not get scheduled for more than 2 minutes, | |
200 | * complain: | |
201 | */ | |
202 | printk(KERN_ERR "INFO: task %s:%d blocked for more than " | |
203 | "%ld seconds.\n", t->comm, t->pid, | |
204 | sysctl_hung_task_timeout_secs); | |
205 | printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" | |
206 | " disables this message.\n"); | |
207 | sched_show_task(t); | |
208 | __debug_show_held_locks(t); | |
209 | ||
210 | t->last_switch_timestamp = now; | |
211 | touch_nmi_watchdog(); | |
9c44bc03 IM |
212 | |
213 | if (softlockup_panic) | |
214 | panic("softlockup: blocked tasks"); | |
82a1fcb9 IM |
215 | } |
216 | ||
217 | /* | |
218 | * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for | |
219 | * a really long time (120 seconds). If that happens, print out | |
220 | * a warning. | |
221 | */ | |
222 | static void check_hung_uninterruptible_tasks(int this_cpu) | |
223 | { | |
224 | int max_count = sysctl_hung_task_check_count; | |
225 | unsigned long now = get_timestamp(this_cpu); | |
226 | struct task_struct *g, *t; | |
227 | ||
228 | /* | |
229 | * If the system crashed already then all bets are off, | |
230 | * do not report extra hung tasks: | |
231 | */ | |
232 | if ((tainted & TAINT_DIE) || did_panic) | |
233 | return; | |
234 | ||
235 | read_lock(&tasklist_lock); | |
236 | do_each_thread(g, t) { | |
237 | if (!--max_count) | |
ed50d6cb | 238 | goto unlock; |
82a1fcb9 IM |
239 | if (t->state & TASK_UNINTERRUPTIBLE) |
240 | check_hung_task(t, now); | |
241 | } while_each_thread(g, t); | |
ed50d6cb | 242 | unlock: |
82a1fcb9 IM |
243 | read_unlock(&tasklist_lock); |
244 | } | |
245 | ||
8446f1d3 IM |
246 | /* |
247 | * The watchdog thread - runs every second and touches the timestamp. | |
248 | */ | |
a5f2ce3c | 249 | static int watchdog(void *__bind_cpu) |
8446f1d3 | 250 | { |
02fb6149 | 251 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |
82a1fcb9 | 252 | int this_cpu = (long)__bind_cpu; |
8446f1d3 IM |
253 | |
254 | sched_setscheduler(current, SCHED_FIFO, ¶m); | |
8446f1d3 | 255 | |
966812dc | 256 | /* initialize timestamp */ |
8c2238ea | 257 | __touch_softlockup_watchdog(); |
966812dc | 258 | |
7be2a03e | 259 | set_current_state(TASK_INTERRUPTIBLE); |
8446f1d3 | 260 | /* |
6687a97d | 261 | * Run briefly once per second to reset the softlockup timestamp. |
82a1fcb9 | 262 | * If this gets delayed for more than 60 seconds then the |
6687a97d | 263 | * debug-printout triggers in softlockup_tick(). |
8446f1d3 IM |
264 | */ |
265 | while (!kthread_should_stop()) { | |
8c2238ea | 266 | __touch_softlockup_watchdog(); |
ed50d6cb PZ |
267 | schedule(); |
268 | ||
269 | if (kthread_should_stop()) | |
270 | break; | |
82a1fcb9 | 271 | |
7be2a03e DA |
272 | if (this_cpu == check_cpu) { |
273 | if (sysctl_hung_task_timeout_secs) | |
274 | check_hung_uninterruptible_tasks(this_cpu); | |
275 | } | |
ed50d6cb | 276 | |
7be2a03e | 277 | set_current_state(TASK_INTERRUPTIBLE); |
8446f1d3 | 278 | } |
7be2a03e | 279 | __set_current_state(TASK_RUNNING); |
8446f1d3 IM |
280 | |
281 | return 0; | |
282 | } | |
283 | ||
284 | /* | |
285 | * Create/destroy watchdog threads as CPUs come and go: | |
286 | */ | |
8c78f307 | 287 | static int __cpuinit |
8446f1d3 IM |
288 | cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) |
289 | { | |
290 | int hotcpu = (unsigned long)hcpu; | |
291 | struct task_struct *p; | |
292 | ||
293 | switch (action) { | |
294 | case CPU_UP_PREPARE: | |
8bb78442 | 295 | case CPU_UP_PREPARE_FROZEN: |
8446f1d3 IM |
296 | BUG_ON(per_cpu(watchdog_task, hotcpu)); |
297 | p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); | |
298 | if (IS_ERR(p)) { | |
a5f2ce3c | 299 | printk(KERN_ERR "watchdog for %i failed\n", hotcpu); |
8446f1d3 IM |
300 | return NOTIFY_BAD; |
301 | } | |
a5f2ce3c IM |
302 | per_cpu(touch_timestamp, hotcpu) = 0; |
303 | per_cpu(watchdog_task, hotcpu) = p; | |
8446f1d3 | 304 | kthread_bind(p, hotcpu); |
a5f2ce3c | 305 | break; |
8446f1d3 | 306 | case CPU_ONLINE: |
8bb78442 | 307 | case CPU_ONLINE_FROZEN: |
82a1fcb9 | 308 | check_cpu = any_online_cpu(cpu_online_map); |
8446f1d3 IM |
309 | wake_up_process(per_cpu(watchdog_task, hotcpu)); |
310 | break; | |
311 | #ifdef CONFIG_HOTPLUG_CPU | |
82a1fcb9 IM |
312 | case CPU_DOWN_PREPARE: |
313 | case CPU_DOWN_PREPARE_FROZEN: | |
314 | if (hotcpu == check_cpu) { | |
315 | cpumask_t temp_cpu_online_map = cpu_online_map; | |
316 | ||
317 | cpu_clear(hotcpu, temp_cpu_online_map); | |
318 | check_cpu = any_online_cpu(temp_cpu_online_map); | |
319 | } | |
320 | break; | |
ed50d6cb PZ |
321 | |
322 | case CPU_UP_CANCELED: | |
323 | case CPU_UP_CANCELED_FROZEN: | |
324 | if (!per_cpu(watchdog_task, hotcpu)) | |
325 | break; | |
326 | /* Unbind so it can run. Fall thru. */ | |
327 | kthread_bind(per_cpu(watchdog_task, hotcpu), | |
328 | any_online_cpu(cpu_online_map)); | |
8446f1d3 | 329 | case CPU_DEAD: |
8bb78442 | 330 | case CPU_DEAD_FROZEN: |
8446f1d3 IM |
331 | p = per_cpu(watchdog_task, hotcpu); |
332 | per_cpu(watchdog_task, hotcpu) = NULL; | |
333 | kthread_stop(p); | |
334 | break; | |
335 | #endif /* CONFIG_HOTPLUG_CPU */ | |
a5f2ce3c | 336 | } |
8446f1d3 IM |
337 | return NOTIFY_OK; |
338 | } | |
339 | ||
8c78f307 | 340 | static struct notifier_block __cpuinitdata cpu_nfb = { |
8446f1d3 IM |
341 | .notifier_call = cpu_callback |
342 | }; | |
343 | ||
344 | __init void spawn_softlockup_task(void) | |
345 | { | |
346 | void *cpu = (void *)(long)smp_processor_id(); | |
07dccf33 | 347 | int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
8446f1d3 | 348 | |
07dccf33 | 349 | BUG_ON(err == NOTIFY_BAD); |
8446f1d3 IM |
350 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
351 | register_cpu_notifier(&cpu_nfb); | |
352 | ||
e041c683 | 353 | atomic_notifier_chain_register(&panic_notifier_list, &panic_block); |
8446f1d3 | 354 | } |