Ignore stolen time in the softlockup watchdog
[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/init.h>
12 #include <linux/delay.h>
13 #include <linux/kthread.h>
14 #include <linux/notifier.h>
15 #include <linux/module.h>
16
17 static DEFINE_SPINLOCK(print_lock);
18
19 static DEFINE_PER_CPU(unsigned long, touch_timestamp);
20 static DEFINE_PER_CPU(unsigned long, print_timestamp);
21 static DEFINE_PER_CPU(struct task_struct *, watchdog_task);
22
23 static int did_panic = 0;
24
25 static int
26 softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
27 {
28         did_panic = 1;
29
30         return NOTIFY_DONE;
31 }
32
33 static struct notifier_block panic_block = {
34         .notifier_call = softlock_panic,
35 };
36
37 /*
38  * Returns seconds, approximately.  We don't need nanosecond
39  * resolution, and we don't need to waste time with a big divide when
40  * 2^30ns == 1.074s.
41  */
42 static unsigned long get_timestamp(void)
43 {
44         return sched_clock() >> 30;  /* 2^30 ~= 10^9 */
45 }
46
47 void touch_softlockup_watchdog(void)
48 {
49         __raw_get_cpu_var(touch_timestamp) = get_timestamp();
50 }
51 EXPORT_SYMBOL(touch_softlockup_watchdog);
52
53 /*
54  * This callback runs from the timer interrupt, and checks
55  * whether the watchdog thread has hung or not:
56  */
57 void softlockup_tick(void)
58 {
59         int this_cpu = smp_processor_id();
60         unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);
61         unsigned long print_timestamp;
62         unsigned long now;
63
64         /* watchdog task hasn't updated timestamp yet */
65         if (touch_timestamp == 0)
66                 return;
67
68         print_timestamp = per_cpu(print_timestamp, this_cpu);
69
70         /* report at most once a second */
71         if (print_timestamp < (touch_timestamp + 1) ||
72                 did_panic ||
73                         !per_cpu(watchdog_task, this_cpu))
74                 return;
75
76         /* do not print during early bootup: */
77         if (unlikely(system_state != SYSTEM_RUNNING)) {
78                 touch_softlockup_watchdog();
79                 return;
80         }
81
82         now = get_timestamp();
83
84         /* Wake up the high-prio watchdog task every second: */
85         if (now > (touch_timestamp + 1))
86                 wake_up_process(per_cpu(watchdog_task, this_cpu));
87
88         /* Warn about unreasonable 10+ seconds delays: */
89         if (now > (touch_timestamp + 10)) {
90                 per_cpu(print_timestamp, this_cpu) = touch_timestamp;
91
92                 spin_lock(&print_lock);
93                 printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n",
94                         this_cpu);
95                 dump_stack();
96                 spin_unlock(&print_lock);
97         }
98 }
99
100 /*
101  * The watchdog thread - runs every second and touches the timestamp.
102  */
103 static int watchdog(void * __bind_cpu)
104 {
105         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
106
107         sched_setscheduler(current, SCHED_FIFO, &param);
108         current->flags |= PF_NOFREEZE;
109
110         /* initialize timestamp */
111         touch_softlockup_watchdog();
112
113         /*
114          * Run briefly once per second to reset the softlockup timestamp.
115          * If this gets delayed for more than 10 seconds then the
116          * debug-printout triggers in softlockup_tick().
117          */
118         while (!kthread_should_stop()) {
119                 set_current_state(TASK_INTERRUPTIBLE);
120                 touch_softlockup_watchdog();
121                 schedule();
122         }
123
124         return 0;
125 }
126
127 /*
128  * Create/destroy watchdog threads as CPUs come and go:
129  */
130 static int __cpuinit
131 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
132 {
133         int hotcpu = (unsigned long)hcpu;
134         struct task_struct *p;
135
136         switch (action) {
137         case CPU_UP_PREPARE:
138                 BUG_ON(per_cpu(watchdog_task, hotcpu));
139                 p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
140                 if (IS_ERR(p)) {
141                         printk("watchdog for %i failed\n", hotcpu);
142                         return NOTIFY_BAD;
143                 }
144                 per_cpu(touch_timestamp, hotcpu) = 0;
145                 per_cpu(watchdog_task, hotcpu) = p;
146                 kthread_bind(p, hotcpu);
147                 break;
148         case CPU_ONLINE:
149                 wake_up_process(per_cpu(watchdog_task, hotcpu));
150                 break;
151 #ifdef CONFIG_HOTPLUG_CPU
152         case CPU_UP_CANCELED:
153                 if (!per_cpu(watchdog_task, hotcpu))
154                         break;
155                 /* Unbind so it can run.  Fall thru. */
156                 kthread_bind(per_cpu(watchdog_task, hotcpu),
157                              any_online_cpu(cpu_online_map));
158         case CPU_DEAD:
159                 p = per_cpu(watchdog_task, hotcpu);
160                 per_cpu(watchdog_task, hotcpu) = NULL;
161                 kthread_stop(p);
162                 break;
163 #endif /* CONFIG_HOTPLUG_CPU */
164         }
165         return NOTIFY_OK;
166 }
167
168 static struct notifier_block __cpuinitdata cpu_nfb = {
169         .notifier_call = cpu_callback
170 };
171
172 __init void spawn_softlockup_task(void)
173 {
174         void *cpu = (void *)(long)smp_processor_id();
175         int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
176
177         BUG_ON(err == NOTIFY_BAD);
178         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
179         register_cpu_notifier(&cpu_nfb);
180
181         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
182 }