softlockup: decouple hung tasks check from softlockup detection
[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/lockdep.h>
17 #include <linux/notifier.h>
18 #include <linux/module.h>
19 #include <linux/sysctl.h>
20
21 #include <asm/irq_regs.h>
22
23 static DEFINE_SPINLOCK(print_lock);
24
25 static DEFINE_PER_CPU(unsigned long, touch_timestamp);
26 static DEFINE_PER_CPU(unsigned long, print_timestamp);
27 static DEFINE_PER_CPU(struct task_struct *, watchdog_task);
28
29 static int __read_mostly did_panic;
30 int __read_mostly softlockup_thresh = 60;
31
32 /*
33  * Should we panic (and reboot, if panic_timeout= is set) when a
34  * soft-lockup occurs:
35  */
36 unsigned int __read_mostly softlockup_panic =
37                                 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
38
39 static int __init softlockup_panic_setup(char *str)
40 {
41         softlockup_panic = simple_strtoul(str, NULL, 0);
42
43         return 1;
44 }
45 __setup("softlockup_panic=", softlockup_panic_setup);
46
47 static int
48 softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
49 {
50         did_panic = 1;
51
52         return NOTIFY_DONE;
53 }
54
55 static struct notifier_block panic_block = {
56         .notifier_call = softlock_panic,
57 };
58
59 /*
60  * Returns seconds, approximately.  We don't need nanosecond
61  * resolution, and we don't need to waste time with a big divide when
62  * 2^30ns == 1.074s.
63  */
64 static unsigned long get_timestamp(int this_cpu)
65 {
66         return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
67 }
68
69 static void __touch_softlockup_watchdog(void)
70 {
71         int this_cpu = raw_smp_processor_id();
72
73         __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu);
74 }
75
76 void touch_softlockup_watchdog(void)
77 {
78         __raw_get_cpu_var(touch_timestamp) = 0;
79 }
80 EXPORT_SYMBOL(touch_softlockup_watchdog);
81
82 void touch_all_softlockup_watchdogs(void)
83 {
84         int cpu;
85
86         /* Cause each CPU to re-update its timestamp rather than complain */
87         for_each_online_cpu(cpu)
88                 per_cpu(touch_timestamp, cpu) = 0;
89 }
90 EXPORT_SYMBOL(touch_all_softlockup_watchdogs);
91
92 int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
93                              struct file *filp, void __user *buffer,
94                              size_t *lenp, loff_t *ppos)
95 {
96         touch_all_softlockup_watchdogs();
97         return proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
98 }
99
100 /*
101  * This callback runs from the timer interrupt, and checks
102  * whether the watchdog thread has hung or not:
103  */
104 void softlockup_tick(void)
105 {
106         int this_cpu = smp_processor_id();
107         unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);
108         unsigned long print_timestamp;
109         struct pt_regs *regs = get_irq_regs();
110         unsigned long now;
111
112         /* Is detection switched off? */
113         if (!per_cpu(watchdog_task, this_cpu) || softlockup_thresh <= 0) {
114                 /* Be sure we don't false trigger if switched back on */
115                 if (touch_timestamp)
116                         per_cpu(touch_timestamp, this_cpu) = 0;
117                 return;
118         }
119
120         if (touch_timestamp == 0) {
121                 __touch_softlockup_watchdog();
122                 return;
123         }
124
125         print_timestamp = per_cpu(print_timestamp, this_cpu);
126
127         /* report at most once a second */
128         if (print_timestamp == touch_timestamp || did_panic)
129                 return;
130
131         /* do not print during early bootup: */
132         if (unlikely(system_state != SYSTEM_RUNNING)) {
133                 __touch_softlockup_watchdog();
134                 return;
135         }
136
137         now = get_timestamp(this_cpu);
138
139         /*
140          * Wake up the high-prio watchdog task twice per
141          * threshold timespan.
142          */
143         if (now > touch_timestamp + softlockup_thresh/2)
144                 wake_up_process(per_cpu(watchdog_task, this_cpu));
145
146         /* Warn about unreasonable delays: */
147         if (now <= (touch_timestamp + softlockup_thresh))
148                 return;
149
150         per_cpu(print_timestamp, this_cpu) = touch_timestamp;
151
152         spin_lock(&print_lock);
153         printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",
154                         this_cpu, now - touch_timestamp,
155                         current->comm, task_pid_nr(current));
156         print_modules();
157         print_irqtrace_events(current);
158         if (regs)
159                 show_regs(regs);
160         else
161                 dump_stack();
162         spin_unlock(&print_lock);
163
164         if (softlockup_panic)
165                 panic("softlockup: hung tasks");
166 }
167
168 /*
169  * The watchdog thread - runs every second and touches the timestamp.
170  */
171 static int watchdog(void *__bind_cpu)
172 {
173         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
174
175         sched_setscheduler(current, SCHED_FIFO, &param);
176
177         /* initialize timestamp */
178         __touch_softlockup_watchdog();
179
180         set_current_state(TASK_INTERRUPTIBLE);
181         /*
182          * Run briefly once per second to reset the softlockup timestamp.
183          * If this gets delayed for more than 60 seconds then the
184          * debug-printout triggers in softlockup_tick().
185          */
186         while (!kthread_should_stop()) {
187                 __touch_softlockup_watchdog();
188                 schedule();
189
190                 if (kthread_should_stop())
191                         break;
192
193                 set_current_state(TASK_INTERRUPTIBLE);
194         }
195         __set_current_state(TASK_RUNNING);
196
197         return 0;
198 }
199
200 /*
201  * Create/destroy watchdog threads as CPUs come and go:
202  */
203 static int __cpuinit
204 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
205 {
206         int hotcpu = (unsigned long)hcpu;
207         struct task_struct *p;
208
209         switch (action) {
210         case CPU_UP_PREPARE:
211         case CPU_UP_PREPARE_FROZEN:
212                 BUG_ON(per_cpu(watchdog_task, hotcpu));
213                 p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
214                 if (IS_ERR(p)) {
215                         printk(KERN_ERR "watchdog for %i failed\n", hotcpu);
216                         return NOTIFY_BAD;
217                 }
218                 per_cpu(touch_timestamp, hotcpu) = 0;
219                 per_cpu(watchdog_task, hotcpu) = p;
220                 kthread_bind(p, hotcpu);
221                 break;
222         case CPU_ONLINE:
223         case CPU_ONLINE_FROZEN:
224                 wake_up_process(per_cpu(watchdog_task, hotcpu));
225                 break;
226 #ifdef CONFIG_HOTPLUG_CPU
227         case CPU_UP_CANCELED:
228         case CPU_UP_CANCELED_FROZEN:
229                 if (!per_cpu(watchdog_task, hotcpu))
230                         break;
231                 /* Unbind so it can run.  Fall thru. */
232                 kthread_bind(per_cpu(watchdog_task, hotcpu),
233                              cpumask_any(cpu_online_mask));
234         case CPU_DEAD:
235         case CPU_DEAD_FROZEN:
236                 p = per_cpu(watchdog_task, hotcpu);
237                 per_cpu(watchdog_task, hotcpu) = NULL;
238                 kthread_stop(p);
239                 break;
240 #endif /* CONFIG_HOTPLUG_CPU */
241         }
242         return NOTIFY_OK;
243 }
244
245 static struct notifier_block __cpuinitdata cpu_nfb = {
246         .notifier_call = cpu_callback
247 };
248
249 static int __initdata nosoftlockup;
250
251 static int __init nosoftlockup_setup(char *str)
252 {
253         nosoftlockup = 1;
254         return 1;
255 }
256 __setup("nosoftlockup", nosoftlockup_setup);
257
258 static int __init spawn_softlockup_task(void)
259 {
260         void *cpu = (void *)(long)smp_processor_id();
261         int err;
262
263         if (nosoftlockup)
264                 return 0;
265
266         err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
267         if (err == NOTIFY_BAD) {
268                 BUG();
269                 return 1;
270         }
271         cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
272         register_cpu_notifier(&cpu_nfb);
273
274         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
275
276         return 0;
277 }
278 early_initcall(spawn_softlockup_task);