Add suspend-related notifications for CPU hotplug
[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 void touch_all_softlockup_watchdogs(void)
54 {
55         int cpu;
56
57         /* Cause each CPU to re-update its timestamp rather than complain */
58         for_each_online_cpu(cpu)
59                 per_cpu(touch_timestamp, cpu) = 0;
60 }
61 EXPORT_SYMBOL(touch_all_softlockup_watchdogs);
62
63 /*
64  * This callback runs from the timer interrupt, and checks
65  * whether the watchdog thread has hung or not:
66  */
67 void softlockup_tick(void)
68 {
69         int this_cpu = smp_processor_id();
70         unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);
71         unsigned long print_timestamp;
72         unsigned long now;
73
74         if (touch_timestamp == 0) {
75                 touch_softlockup_watchdog();
76                 return;
77         }
78
79         print_timestamp = per_cpu(print_timestamp, this_cpu);
80
81         /* report at most once a second */
82         if (print_timestamp < (touch_timestamp + 1) ||
83                 did_panic ||
84                         !per_cpu(watchdog_task, this_cpu))
85                 return;
86
87         /* do not print during early bootup: */
88         if (unlikely(system_state != SYSTEM_RUNNING)) {
89                 touch_softlockup_watchdog();
90                 return;
91         }
92
93         now = get_timestamp();
94
95         /* Wake up the high-prio watchdog task every second: */
96         if (now > (touch_timestamp + 1))
97                 wake_up_process(per_cpu(watchdog_task, this_cpu));
98
99         /* Warn about unreasonable 10+ seconds delays: */
100         if (now > (touch_timestamp + 10)) {
101                 per_cpu(print_timestamp, this_cpu) = touch_timestamp;
102
103                 spin_lock(&print_lock);
104                 printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n",
105                         this_cpu);
106                 dump_stack();
107                 spin_unlock(&print_lock);
108         }
109 }
110
111 /*
112  * The watchdog thread - runs every second and touches the timestamp.
113  */
114 static int watchdog(void * __bind_cpu)
115 {
116         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
117
118         sched_setscheduler(current, SCHED_FIFO, &param);
119         current->flags |= PF_NOFREEZE;
120
121         /* initialize timestamp */
122         touch_softlockup_watchdog();
123
124         /*
125          * Run briefly once per second to reset the softlockup timestamp.
126          * If this gets delayed for more than 10 seconds then the
127          * debug-printout triggers in softlockup_tick().
128          */
129         while (!kthread_should_stop()) {
130                 set_current_state(TASK_INTERRUPTIBLE);
131                 touch_softlockup_watchdog();
132                 schedule();
133         }
134
135         return 0;
136 }
137
138 /*
139  * Create/destroy watchdog threads as CPUs come and go:
140  */
141 static int __cpuinit
142 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
143 {
144         int hotcpu = (unsigned long)hcpu;
145         struct task_struct *p;
146
147         switch (action) {
148         case CPU_UP_PREPARE:
149         case CPU_UP_PREPARE_FROZEN:
150                 BUG_ON(per_cpu(watchdog_task, hotcpu));
151                 p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
152                 if (IS_ERR(p)) {
153                         printk("watchdog for %i failed\n", hotcpu);
154                         return NOTIFY_BAD;
155                 }
156                 per_cpu(touch_timestamp, hotcpu) = 0;
157                 per_cpu(watchdog_task, hotcpu) = p;
158                 kthread_bind(p, hotcpu);
159                 break;
160         case CPU_ONLINE:
161         case CPU_ONLINE_FROZEN:
162                 wake_up_process(per_cpu(watchdog_task, hotcpu));
163                 break;
164 #ifdef CONFIG_HOTPLUG_CPU
165         case CPU_UP_CANCELED:
166         case CPU_UP_CANCELED_FROZEN:
167                 if (!per_cpu(watchdog_task, hotcpu))
168                         break;
169                 /* Unbind so it can run.  Fall thru. */
170                 kthread_bind(per_cpu(watchdog_task, hotcpu),
171                              any_online_cpu(cpu_online_map));
172         case CPU_DEAD:
173         case CPU_DEAD_FROZEN:
174                 p = per_cpu(watchdog_task, hotcpu);
175                 per_cpu(watchdog_task, hotcpu) = NULL;
176                 kthread_stop(p);
177                 break;
178 #endif /* CONFIG_HOTPLUG_CPU */
179         }
180         return NOTIFY_OK;
181 }
182
183 static struct notifier_block __cpuinitdata cpu_nfb = {
184         .notifier_call = cpu_callback
185 };
186
187 __init void spawn_softlockup_task(void)
188 {
189         void *cpu = (void *)(long)smp_processor_id();
190         int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
191
192         BUG_ON(err == NOTIFY_BAD);
193         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
194         register_cpu_notifier(&cpu_nfb);
195
196         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
197 }