01b6522fd92bc0b28f7df00eb66876a389b34908
[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/notifier.h>
17 #include <linux/module.h>
18
19 #include <asm/irq_regs.h>
20
21 static DEFINE_SPINLOCK(print_lock);
22
23 static DEFINE_PER_CPU(unsigned long, touch_timestamp);
24 static DEFINE_PER_CPU(unsigned long, print_timestamp);
25 static DEFINE_PER_CPU(struct task_struct *, watchdog_task);
26
27 static int __read_mostly did_panic;
28 unsigned long __read_mostly softlockup_thresh = 60;
29
30 static int
31 softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
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
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  */
47 static unsigned long get_timestamp(int this_cpu)
48 {
49         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
50 }
51
52 void touch_softlockup_watchdog(void)
53 {
54         int this_cpu = raw_smp_processor_id();
55
56         __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu);
57 }
58 EXPORT_SYMBOL(touch_softlockup_watchdog);
59
60 void touch_all_softlockup_watchdogs(void)
61 {
62         int cpu;
63
64         /* Cause each CPU to re-update its timestamp rather than complain */
65         for_each_online_cpu(cpu)
66                 per_cpu(touch_timestamp, cpu) = 0;
67 }
68 EXPORT_SYMBOL(touch_all_softlockup_watchdogs);
69
70 /*
71  * This callback runs from the timer interrupt, and checks
72  * whether the watchdog thread has hung or not:
73  */
74 void softlockup_tick(void)
75 {
76         int this_cpu = smp_processor_id();
77         unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);
78         unsigned long print_timestamp;
79         struct pt_regs *regs = get_irq_regs();
80         unsigned long now;
81
82         if (touch_timestamp == 0) {
83                 touch_softlockup_watchdog();
84                 return;
85         }
86
87         print_timestamp = per_cpu(print_timestamp, this_cpu);
88
89         /* report at most once a second */
90         if ((print_timestamp >= touch_timestamp &&
91                         print_timestamp < (touch_timestamp + 1)) ||
92                         did_panic || !per_cpu(watchdog_task, this_cpu)) {
93                 return;
94         }
95
96         /* do not print during early bootup: */
97         if (unlikely(system_state != SYSTEM_RUNNING)) {
98                 touch_softlockup_watchdog();
99                 return;
100         }
101
102         now = get_timestamp(this_cpu);
103
104         /* Wake up the high-prio watchdog task every second: */
105         if (now > (touch_timestamp + 1))
106                 wake_up_process(per_cpu(watchdog_task, this_cpu));
107
108         /* Warn about unreasonable delays: */
109         if (now <= (touch_timestamp + softlockup_thresh))
110                 return;
111
112         per_cpu(print_timestamp, this_cpu) = touch_timestamp;
113
114         spin_lock(&print_lock);
115         printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",
116                         this_cpu, now - touch_timestamp,
117                         current->comm, task_pid_nr(current));
118         if (regs)
119                 show_regs(regs);
120         else
121                 dump_stack();
122         spin_unlock(&print_lock);
123 }
124
125 /*
126  * Have a reasonable limit on the number of tasks checked:
127  */
128 unsigned long __read_mostly sysctl_hung_task_check_count = 1024;
129
130 /*
131  * Zero means infinite timeout - no checking done:
132  */
133 unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120;
134
135 unsigned long __read_mostly sysctl_hung_task_warnings = 10;
136
137 /*
138  * Only do the hung-tasks check on one CPU:
139  */
140 static int check_cpu __read_mostly = -1;
141
142 static void check_hung_task(struct task_struct *t, unsigned long now)
143 {
144         unsigned long switch_count = t->nvcsw + t->nivcsw;
145
146         if (t->flags & PF_FROZEN)
147                 return;
148
149         if (switch_count != t->last_switch_count || !t->last_switch_timestamp) {
150                 t->last_switch_count = switch_count;
151                 t->last_switch_timestamp = now;
152                 return;
153         }
154         if ((long)(now - t->last_switch_timestamp) <
155                                         sysctl_hung_task_timeout_secs)
156                 return;
157         if (sysctl_hung_task_warnings < 0)
158                 return;
159         sysctl_hung_task_warnings--;
160
161         /*
162          * Ok, the task did not get scheduled for more than 2 minutes,
163          * complain:
164          */
165         printk(KERN_ERR "INFO: task %s:%d blocked for more than "
166                         "%ld seconds.\n", t->comm, t->pid,
167                         sysctl_hung_task_timeout_secs);
168         printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
169                         " disables this message.\n");
170         sched_show_task(t);
171         __debug_show_held_locks(t);
172
173         t->last_switch_timestamp = now;
174         touch_nmi_watchdog();
175 }
176
177 /*
178  * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for
179  * a really long time (120 seconds). If that happens, print out
180  * a warning.
181  */
182 static void check_hung_uninterruptible_tasks(int this_cpu)
183 {
184         int max_count = sysctl_hung_task_check_count;
185         unsigned long now = get_timestamp(this_cpu);
186         struct task_struct *g, *t;
187
188         /*
189          * If the system crashed already then all bets are off,
190          * do not report extra hung tasks:
191          */
192         if ((tainted & TAINT_DIE) || did_panic)
193                 return;
194
195         read_lock(&tasklist_lock);
196         do_each_thread(g, t) {
197                 if (!--max_count)
198                         goto unlock;
199                 if (t->state & TASK_UNINTERRUPTIBLE)
200                         check_hung_task(t, now);
201         } while_each_thread(g, t);
202  unlock:
203         read_unlock(&tasklist_lock);
204 }
205
206 /*
207  * The watchdog thread - runs every second and touches the timestamp.
208  */
209 static int watchdog(void *__bind_cpu)
210 {
211         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
212         int this_cpu = (long)__bind_cpu;
213
214         sched_setscheduler(current, SCHED_FIFO, &param);
215
216         /* initialize timestamp */
217         touch_softlockup_watchdog();
218
219         set_current_state(TASK_INTERRUPTIBLE);
220         /*
221          * Run briefly once per second to reset the softlockup timestamp.
222          * If this gets delayed for more than 60 seconds then the
223          * debug-printout triggers in softlockup_tick().
224          */
225         while (!kthread_should_stop()) {
226                 touch_softlockup_watchdog();
227                 schedule();
228
229                 if (kthread_should_stop())
230                         break;
231
232                 if (this_cpu == check_cpu) {
233                         if (sysctl_hung_task_timeout_secs)
234                                 check_hung_uninterruptible_tasks(this_cpu);
235                 }
236
237                 set_current_state(TASK_INTERRUPTIBLE);
238         }
239         __set_current_state(TASK_RUNNING);
240
241         return 0;
242 }
243
244 /*
245  * Create/destroy watchdog threads as CPUs come and go:
246  */
247 static int __cpuinit
248 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
249 {
250         int hotcpu = (unsigned long)hcpu;
251         struct task_struct *p;
252
253         switch (action) {
254         case CPU_UP_PREPARE:
255         case CPU_UP_PREPARE_FROZEN:
256                 BUG_ON(per_cpu(watchdog_task, hotcpu));
257                 p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
258                 if (IS_ERR(p)) {
259                         printk(KERN_ERR "watchdog for %i failed\n", hotcpu);
260                         return NOTIFY_BAD;
261                 }
262                 per_cpu(touch_timestamp, hotcpu) = 0;
263                 per_cpu(watchdog_task, hotcpu) = p;
264                 kthread_bind(p, hotcpu);
265                 break;
266         case CPU_ONLINE:
267         case CPU_ONLINE_FROZEN:
268                 check_cpu = any_online_cpu(cpu_online_map);
269                 wake_up_process(per_cpu(watchdog_task, hotcpu));
270                 break;
271 #ifdef CONFIG_HOTPLUG_CPU
272         case CPU_DOWN_PREPARE:
273         case CPU_DOWN_PREPARE_FROZEN:
274                 if (hotcpu == check_cpu) {
275                         cpumask_t temp_cpu_online_map = cpu_online_map;
276
277                         cpu_clear(hotcpu, temp_cpu_online_map);
278                         check_cpu = any_online_cpu(temp_cpu_online_map);
279                 }
280                 break;
281
282         case CPU_UP_CANCELED:
283         case CPU_UP_CANCELED_FROZEN:
284                 if (!per_cpu(watchdog_task, hotcpu))
285                         break;
286                 /* Unbind so it can run.  Fall thru. */
287                 kthread_bind(per_cpu(watchdog_task, hotcpu),
288                              any_online_cpu(cpu_online_map));
289         case CPU_DEAD:
290         case CPU_DEAD_FROZEN:
291                 p = per_cpu(watchdog_task, hotcpu);
292                 per_cpu(watchdog_task, hotcpu) = NULL;
293                 kthread_stop(p);
294                 break;
295 #endif /* CONFIG_HOTPLUG_CPU */
296         }
297         return NOTIFY_OK;
298 }
299
300 static struct notifier_block __cpuinitdata cpu_nfb = {
301         .notifier_call = cpu_callback
302 };
303
304 __init void spawn_softlockup_task(void)
305 {
306         void *cpu = (void *)(long)smp_processor_id();
307         int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
308
309         BUG_ON(err == NOTIFY_BAD);
310         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
311         register_cpu_notifier(&cpu_nfb);
312
313         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
314 }