softlockup watchdog: style cleanups
[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/freezer.h>
14 #include <linux/kthread.h>
15 #include <linux/notifier.h>
16 #include <linux/module.h>
17
18 #include <asm/irq_regs.h>
19
20 static DEFINE_SPINLOCK(print_lock);
21
22 static DEFINE_PER_CPU(unsigned long, touch_timestamp);
23 static DEFINE_PER_CPU(unsigned long, print_timestamp);
24 static DEFINE_PER_CPU(struct task_struct *, watchdog_task);
25
26 static int did_panic;
27
28 static int
29 softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
30 {
31         did_panic = 1;
32
33         return NOTIFY_DONE;
34 }
35
36 static struct notifier_block panic_block = {
37         .notifier_call = softlock_panic,
38 };
39
40 /*
41  * Returns seconds, approximately.  We don't need nanosecond
42  * resolution, and we don't need to waste time with a big divide when
43  * 2^30ns == 1.074s.
44  */
45 static unsigned long get_timestamp(int this_cpu)
46 {
47         return cpu_clock(this_cpu) >> 30;  /* 2^30 ~= 10^9 */
48 }
49
50 void touch_softlockup_watchdog(void)
51 {
52         int this_cpu = raw_smp_processor_id();
53
54         __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu);
55 }
56 EXPORT_SYMBOL(touch_softlockup_watchdog);
57
58 void touch_all_softlockup_watchdogs(void)
59 {
60         int cpu;
61
62         /* Cause each CPU to re-update its timestamp rather than complain */
63         for_each_online_cpu(cpu)
64                 per_cpu(touch_timestamp, cpu) = 0;
65 }
66 EXPORT_SYMBOL(touch_all_softlockup_watchdogs);
67
68 /*
69  * This callback runs from the timer interrupt, and checks
70  * whether the watchdog thread has hung or not:
71  */
72 void softlockup_tick(void)
73 {
74         int this_cpu = smp_processor_id();
75         unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);
76         unsigned long print_timestamp;
77         struct pt_regs *regs = get_irq_regs();
78         unsigned long now;
79
80         if (touch_timestamp == 0) {
81                 touch_softlockup_watchdog();
82                 return;
83         }
84
85         print_timestamp = per_cpu(print_timestamp, this_cpu);
86
87         /* report at most once a second */
88         if ((print_timestamp >= touch_timestamp &&
89                         print_timestamp < (touch_timestamp + 1)) ||
90                         did_panic || !per_cpu(watchdog_task, this_cpu)) {
91                 return;
92         }
93
94         /* do not print during early bootup: */
95         if (unlikely(system_state != SYSTEM_RUNNING)) {
96                 touch_softlockup_watchdog();
97                 return;
98         }
99
100         now = get_timestamp(this_cpu);
101
102         /* Wake up the high-prio watchdog task every second: */
103         if (now > (touch_timestamp + 1))
104                 wake_up_process(per_cpu(watchdog_task, this_cpu));
105
106         /* Warn about unreasonable 10+ seconds delays: */
107         if (now <= (touch_timestamp + 10))
108                 return;
109
110         per_cpu(print_timestamp, this_cpu) = touch_timestamp;
111
112         spin_lock(&print_lock);
113         printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n", this_cpu);
114         if (regs)
115                 show_regs(regs);
116         else
117                 dump_stack();
118         spin_unlock(&print_lock);
119 }
120
121 /*
122  * The watchdog thread - runs every second and touches the timestamp.
123  */
124 static int watchdog(void *__bind_cpu)
125 {
126         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
127
128         sched_setscheduler(current, SCHED_FIFO, &param);
129
130         /* initialize timestamp */
131         touch_softlockup_watchdog();
132
133         /*
134          * Run briefly once per second to reset the softlockup timestamp.
135          * If this gets delayed for more than 10 seconds then the
136          * debug-printout triggers in softlockup_tick().
137          */
138         while (!kthread_should_stop()) {
139                 set_current_state(TASK_INTERRUPTIBLE);
140                 touch_softlockup_watchdog();
141                 schedule();
142         }
143
144         return 0;
145 }
146
147 /*
148  * Create/destroy watchdog threads as CPUs come and go:
149  */
150 static int __cpuinit
151 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
152 {
153         int hotcpu = (unsigned long)hcpu;
154         struct task_struct *p;
155
156         switch (action) {
157         case CPU_UP_PREPARE:
158         case CPU_UP_PREPARE_FROZEN:
159                 BUG_ON(per_cpu(watchdog_task, hotcpu));
160                 p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
161                 if (IS_ERR(p)) {
162                         printk(KERN_ERR "watchdog for %i failed\n", hotcpu);
163                         return NOTIFY_BAD;
164                 }
165                 per_cpu(touch_timestamp, hotcpu) = 0;
166                 per_cpu(watchdog_task, hotcpu) = p;
167                 kthread_bind(p, hotcpu);
168                 break;
169         case CPU_ONLINE:
170         case CPU_ONLINE_FROZEN:
171                 wake_up_process(per_cpu(watchdog_task, hotcpu));
172                 break;
173 #ifdef CONFIG_HOTPLUG_CPU
174         case CPU_UP_CANCELED:
175         case CPU_UP_CANCELED_FROZEN:
176                 if (!per_cpu(watchdog_task, hotcpu))
177                         break;
178                 /* Unbind so it can run.  Fall thru. */
179                 kthread_bind(per_cpu(watchdog_task, hotcpu),
180                              any_online_cpu(cpu_online_map));
181         case CPU_DEAD:
182         case CPU_DEAD_FROZEN:
183                 p = per_cpu(watchdog_task, hotcpu);
184                 per_cpu(watchdog_task, hotcpu) = NULL;
185                 kthread_stop(p);
186                 break;
187 #endif /* CONFIG_HOTPLUG_CPU */
188         }
189         return NOTIFY_OK;
190 }
191
192 static struct notifier_block __cpuinitdata cpu_nfb = {
193         .notifier_call = cpu_callback
194 };
195
196 __init void spawn_softlockup_task(void)
197 {
198         void *cpu = (void *)(long)smp_processor_id();
199         int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
200
201         BUG_ON(err == NOTIFY_BAD);
202         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
203         register_cpu_notifier(&cpu_nfb);
204
205         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
206 }