projects/linux·blob v2.6.21 · refs

159 lines · 4.0 KiB

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