softlockup: fix watchdog task wakeup frequency
[linux-2.6.git] / kernel / softlockup.c
1 /*
2  * Detect Soft Lockups
3  *
4  * started by Ingo Molnar, Copyright (C) 2005, 2006 Red Hat, Inc.
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  */
9 #include <linux/mm.h>
10 #include <linux/cpu.h>
11 #include <linux/nmi.h>
12 #include <linux/init.h>
13 #include <linux/delay.h>
14 #include <linux/freezer.h>
15 #include <linux/kthread.h>
16 #include <linux/lockdep.h>
17 #include <linux/notifier.h>
18 #include <linux/module.h>
19
20 #include <asm/irq_regs.h>
21
22 static DEFINE_SPINLOCK(print_lock);
23
24 static DEFINE_PER_CPU(unsigned long, touch_timestamp);
25 static DEFINE_PER_CPU(unsigned long, print_timestamp);
26 static DEFINE_PER_CPU(struct task_struct *, watchdog_task);
27
28 static int __read_mostly did_panic;
29 int __read_mostly softlockup_thresh = 60;
30
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
46 static int
47 softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
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
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  */
63 static unsigned long get_timestamp(int this_cpu)
64 {
65         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
66 }
67
68 static void __touch_softlockup_watchdog(void)
69 {
70         int this_cpu = raw_smp_processor_id();
71
72         __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu);
73 }
74
75 void touch_softlockup_watchdog(void)
76 {
77         __raw_get_cpu_var(touch_timestamp) = 0;
78 }
79 EXPORT_SYMBOL(touch_softlockup_watchdog);
80
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
91 /*
92  * This callback runs from the timer interrupt, and checks
93  * whether the watchdog thread has hung or not:
94  */
95 void softlockup_tick(void)
96 {
97         int this_cpu = smp_processor_id();
98         unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);
99         unsigned long print_timestamp;
100         struct pt_regs *regs = get_irq_regs();
101         unsigned long now;
102
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
111         if (touch_timestamp == 0) {
112                 __touch_softlockup_watchdog();
113                 return;
114         }
115
116         print_timestamp = per_cpu(print_timestamp, this_cpu);
117
118         /* report at most once a second */
119         if (print_timestamp == touch_timestamp || did_panic)
120                 return;
121
122         /* do not print during early bootup: */
123         if (unlikely(system_state != SYSTEM_RUNNING)) {
124                 __touch_softlockup_watchdog();
125                 return;
126         }
127
128         now = get_timestamp(this_cpu);
129
130         /*
131          * Wake up the high-prio watchdog task twice per
132          * threshold timespan.
133          */
134         if (now > touch_timestamp + softlockup_thresh/2)
135                 wake_up_process(per_cpu(watchdog_task, this_cpu));
136
137         /* Warn about unreasonable delays: */
138         if (now <= (touch_timestamp + softlockup_thresh))
139                 return;
140
141         per_cpu(print_timestamp, this_cpu) = touch_timestamp;
142
143         spin_lock(&print_lock);
144         printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",
145                         this_cpu, now - touch_timestamp,
146                         current->comm, task_pid_nr(current));
147         print_modules();
148         print_irqtrace_events(current);
149         if (regs)
150                 show_regs(regs);
151         else
152                 dump_stack();
153         spin_unlock(&print_lock);
154
155         if (softlockup_panic)
156                 panic("softlockup: hung tasks");
157 }
158
159 /*
160  * Have a reasonable limit on the number of tasks checked:
161  */
162 unsigned long __read_mostly sysctl_hung_task_check_count = 1024;
163
164 /*
165  * Zero means infinite timeout - no checking done:
166  */
167 unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120;
168
169 unsigned long __read_mostly sysctl_hung_task_warnings = 10;
170
171 /*
172  * Only do the hung-tasks check on one CPU:
173  */
174 static int check_cpu __read_mostly = -1;
175
176 static void check_hung_task(struct task_struct *t, unsigned long now)
177 {
178         unsigned long switch_count = t->nvcsw + t->nivcsw;
179
180         if (t->flags & PF_FROZEN)
181                 return;
182
183         if (switch_count != t->last_switch_count || !t->last_switch_timestamp) {
184                 t->last_switch_count = switch_count;
185                 t->last_switch_timestamp = now;
186                 return;
187         }
188         if ((long)(now - t->last_switch_timestamp) <
189                                         sysctl_hung_task_timeout_secs)
190                 return;
191         if (sysctl_hung_task_warnings < 0)
192                 return;
193         sysctl_hung_task_warnings--;
194
195         /*
196          * Ok, the task did not get scheduled for more than 2 minutes,
197          * complain:
198          */
199         printk(KERN_ERR "INFO: task %s:%d blocked for more than "
200                         "%ld seconds.\n", t->comm, t->pid,
201                         sysctl_hung_task_timeout_secs);
202         printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
203                         " disables this message.\n");
204         sched_show_task(t);
205         __debug_show_held_locks(t);
206
207         t->last_switch_timestamp = now;
208         touch_nmi_watchdog();
209
210         if (softlockup_panic)
211                 panic("softlockup: blocked tasks");
212 }
213
214 /*
215  * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for
216  * a really long time (120 seconds). If that happens, print out
217  * a warning.
218  */
219 static void check_hung_uninterruptible_tasks(int this_cpu)
220 {
221         int max_count = sysctl_hung_task_check_count;
222         unsigned long now = get_timestamp(this_cpu);
223         struct task_struct *g, *t;
224
225         /*
226          * If the system crashed already then all bets are off,
227          * do not report extra hung tasks:
228          */
229         if ((tainted & TAINT_DIE) || did_panic)
230                 return;
231
232         read_lock(&tasklist_lock);
233         do_each_thread(g, t) {
234                 if (!--max_count)
235                         goto unlock;
236                 if (t->state & TASK_UNINTERRUPTIBLE)
237                         check_hung_task(t, now);
238         } while_each_thread(g, t);
239  unlock:
240         read_unlock(&tasklist_lock);
241 }
242
243 /*
244  * The watchdog thread - runs every second and touches the timestamp.
245  */
246 static int watchdog(void *__bind_cpu)
247 {
248         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
249         int this_cpu = (long)__bind_cpu;
250
251         sched_setscheduler(current, SCHED_FIFO, &param);
252
253         /* initialize timestamp */
254         __touch_softlockup_watchdog();
255
256         set_current_state(TASK_INTERRUPTIBLE);
257         /*
258          * Run briefly once per second to reset the softlockup timestamp.
259          * If this gets delayed for more than 60 seconds then the
260          * debug-printout triggers in softlockup_tick().
261          */
262         while (!kthread_should_stop()) {
263                 __touch_softlockup_watchdog();
264                 schedule();
265
266                 if (kthread_should_stop())
267                         break;
268
269                 if (this_cpu == check_cpu) {
270                         if (sysctl_hung_task_timeout_secs)
271                                 check_hung_uninterruptible_tasks(this_cpu);
272                 }
273
274                 set_current_state(TASK_INTERRUPTIBLE);
275         }
276         __set_current_state(TASK_RUNNING);
277
278         return 0;
279 }
280
281 /*
282  * Create/destroy watchdog threads as CPUs come and go:
283  */
284 static int __cpuinit
285 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
286 {
287         int hotcpu = (unsigned long)hcpu;
288         struct task_struct *p;
289
290         switch (action) {
291         case CPU_UP_PREPARE:
292         case CPU_UP_PREPARE_FROZEN:
293                 BUG_ON(per_cpu(watchdog_task, hotcpu));
294                 p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
295                 if (IS_ERR(p)) {
296                         printk(KERN_ERR "watchdog for %i failed\n", hotcpu);
297                         return NOTIFY_BAD;
298                 }
299                 per_cpu(touch_timestamp, hotcpu) = 0;
300                 per_cpu(watchdog_task, hotcpu) = p;
301                 kthread_bind(p, hotcpu);
302                 break;
303         case CPU_ONLINE:
304         case CPU_ONLINE_FROZEN:
305                 check_cpu = any_online_cpu(cpu_online_map);
306                 wake_up_process(per_cpu(watchdog_task, hotcpu));
307                 break;
308 #ifdef CONFIG_HOTPLUG_CPU
309         case CPU_DOWN_PREPARE:
310         case CPU_DOWN_PREPARE_FROZEN:
311                 if (hotcpu == check_cpu) {
312                         cpumask_t temp_cpu_online_map = cpu_online_map;
313
314                         cpu_clear(hotcpu, temp_cpu_online_map);
315                         check_cpu = any_online_cpu(temp_cpu_online_map);
316                 }
317                 break;
318
319         case CPU_UP_CANCELED:
320         case CPU_UP_CANCELED_FROZEN:
321                 if (!per_cpu(watchdog_task, hotcpu))
322                         break;
323                 /* Unbind so it can run.  Fall thru. */
324                 kthread_bind(per_cpu(watchdog_task, hotcpu),
325                              any_online_cpu(cpu_online_map));
326         case CPU_DEAD:
327         case CPU_DEAD_FROZEN:
328                 p = per_cpu(watchdog_task, hotcpu);
329                 per_cpu(watchdog_task, hotcpu) = NULL;
330                 kthread_stop(p);
331                 break;
332 #endif /* CONFIG_HOTPLUG_CPU */
333         }
334         return NOTIFY_OK;
335 }
336
337 static struct notifier_block __cpuinitdata cpu_nfb = {
338         .notifier_call = cpu_callback
339 };
340
341 __init void spawn_softlockup_task(void)
342 {
343         void *cpu = (void *)(long)smp_processor_id();
344         int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
345
346         BUG_ON(err == NOTIFY_BAD);
347         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
348         register_cpu_notifier(&cpu_nfb);
349
350         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
351 }