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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, softlockup_touch_ts); /* touch timestamp */ | |
26 | static DEFINE_PER_CPU(unsigned long, softlockup_print_ts); /* print timestamp */ | |
27 | static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); | |
28 | static DEFINE_PER_CPU(bool, softlock_touch_sync); | |
29 | ||
30 | static int __read_mostly did_panic; | |
31 | int __read_mostly softlockup_thresh = 60; | |
32 | ||
33 | /* | |
34 | * Should we panic (and reboot, if panic_timeout= is set) when a | |
35 | * soft-lockup occurs: | |
36 | */ | |
37 | unsigned int __read_mostly softlockup_panic = | |
38 | CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; | |
39 | ||
40 | static int __init softlockup_panic_setup(char *str) | |
41 | { | |
42 | softlockup_panic = simple_strtoul(str, NULL, 0); | |
43 | ||
44 | return 1; | |
45 | } | |
46 | __setup("softlockup_panic=", softlockup_panic_setup); | |
47 | ||
48 | static int | |
49 | softlock_panic(struct notifier_block *this, unsigned long event, void *ptr) | |
50 | { | |
51 | did_panic = 1; | |
52 | ||
53 | return NOTIFY_DONE; | |
54 | } | |
55 | ||
56 | static struct notifier_block panic_block = { | |
57 | .notifier_call = softlock_panic, | |
58 | }; | |
59 | ||
60 | /* | |
61 | * Returns seconds, approximately. We don't need nanosecond | |
62 | * resolution, and we don't need to waste time with a big divide when | |
63 | * 2^30ns == 1.074s. | |
64 | */ | |
65 | static unsigned long get_timestamp(int this_cpu) | |
66 | { | |
67 | return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ | |
68 | } | |
69 | ||
70 | static void __touch_softlockup_watchdog(void) | |
71 | { | |
72 | int this_cpu = raw_smp_processor_id(); | |
73 | ||
74 | __raw_get_cpu_var(softlockup_touch_ts) = get_timestamp(this_cpu); | |
75 | } | |
76 | ||
77 | void touch_softlockup_watchdog(void) | |
78 | { | |
79 | __raw_get_cpu_var(softlockup_touch_ts) = 0; | |
80 | } | |
81 | EXPORT_SYMBOL(touch_softlockup_watchdog); | |
82 | ||
83 | void touch_softlockup_watchdog_sync(void) | |
84 | { | |
85 | __raw_get_cpu_var(softlock_touch_sync) = true; | |
86 | __raw_get_cpu_var(softlockup_touch_ts) = 0; | |
87 | } | |
88 | ||
89 | void touch_all_softlockup_watchdogs(void) | |
90 | { | |
91 | int cpu; | |
92 | ||
93 | /* Cause each CPU to re-update its timestamp rather than complain */ | |
94 | for_each_online_cpu(cpu) | |
95 | per_cpu(softlockup_touch_ts, cpu) = 0; | |
96 | } | |
97 | EXPORT_SYMBOL(touch_all_softlockup_watchdogs); | |
98 | ||
99 | int proc_dosoftlockup_thresh(struct ctl_table *table, int write, | |
100 | void __user *buffer, | |
101 | size_t *lenp, loff_t *ppos) | |
102 | { | |
103 | touch_all_softlockup_watchdogs(); | |
104 | return proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
105 | } | |
106 | ||
107 | /* | |
108 | * This callback runs from the timer interrupt, and checks | |
109 | * whether the watchdog thread has hung or not: | |
110 | */ | |
111 | void softlockup_tick(void) | |
112 | { | |
113 | int this_cpu = smp_processor_id(); | |
114 | unsigned long touch_ts = per_cpu(softlockup_touch_ts, this_cpu); | |
115 | unsigned long print_ts; | |
116 | struct pt_regs *regs = get_irq_regs(); | |
117 | unsigned long now; | |
118 | ||
119 | /* Is detection switched off? */ | |
120 | if (!per_cpu(softlockup_watchdog, this_cpu) || softlockup_thresh <= 0) { | |
121 | /* Be sure we don't false trigger if switched back on */ | |
122 | if (touch_ts) | |
123 | per_cpu(softlockup_touch_ts, this_cpu) = 0; | |
124 | return; | |
125 | } | |
126 | ||
127 | if (touch_ts == 0) { | |
128 | if (unlikely(per_cpu(softlock_touch_sync, this_cpu))) { | |
129 | /* | |
130 | * If the time stamp was touched atomically | |
131 | * make sure the scheduler tick is up to date. | |
132 | */ | |
133 | per_cpu(softlock_touch_sync, this_cpu) = false; | |
134 | sched_clock_tick(); | |
135 | } | |
136 | __touch_softlockup_watchdog(); | |
137 | return; | |
138 | } | |
139 | ||
140 | print_ts = per_cpu(softlockup_print_ts, this_cpu); | |
141 | ||
142 | /* report at most once a second */ | |
143 | if (print_ts == touch_ts || did_panic) | |
144 | return; | |
145 | ||
146 | /* do not print during early bootup: */ | |
147 | if (unlikely(system_state != SYSTEM_RUNNING)) { | |
148 | __touch_softlockup_watchdog(); | |
149 | return; | |
150 | } | |
151 | ||
152 | now = get_timestamp(this_cpu); | |
153 | ||
154 | /* | |
155 | * Wake up the high-prio watchdog task twice per | |
156 | * threshold timespan. | |
157 | */ | |
158 | if (time_after(now - softlockup_thresh/2, touch_ts)) | |
159 | wake_up_process(per_cpu(softlockup_watchdog, this_cpu)); | |
160 | ||
161 | /* Warn about unreasonable delays: */ | |
162 | if (time_before_eq(now - softlockup_thresh, touch_ts)) | |
163 | return; | |
164 | ||
165 | per_cpu(softlockup_print_ts, this_cpu) = touch_ts; | |
166 | ||
167 | spin_lock(&print_lock); | |
168 | printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n", | |
169 | this_cpu, now - touch_ts, | |
170 | current->comm, task_pid_nr(current)); | |
171 | print_modules(); | |
172 | print_irqtrace_events(current); | |
173 | if (regs) | |
174 | show_regs(regs); | |
175 | else | |
176 | dump_stack(); | |
177 | spin_unlock(&print_lock); | |
178 | ||
179 | if (softlockup_panic) | |
180 | panic("softlockup: hung tasks"); | |
181 | } | |
182 | ||
183 | /* | |
184 | * The watchdog thread - runs every second and touches the timestamp. | |
185 | */ | |
186 | static int watchdog(void *__bind_cpu) | |
187 | { | |
188 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; | |
189 | ||
190 | sched_setscheduler(current, SCHED_FIFO, ¶m); | |
191 | ||
192 | /* initialize timestamp */ | |
193 | __touch_softlockup_watchdog(); | |
194 | ||
195 | set_current_state(TASK_INTERRUPTIBLE); | |
196 | /* | |
197 | * Run briefly once per second to reset the softlockup timestamp. | |
198 | * If this gets delayed for more than 60 seconds then the | |
199 | * debug-printout triggers in softlockup_tick(). | |
200 | */ | |
201 | while (!kthread_should_stop()) { | |
202 | __touch_softlockup_watchdog(); | |
203 | schedule(); | |
204 | ||
205 | if (kthread_should_stop()) | |
206 | break; | |
207 | ||
208 | set_current_state(TASK_INTERRUPTIBLE); | |
209 | } | |
210 | __set_current_state(TASK_RUNNING); | |
211 | ||
212 | return 0; | |
213 | } | |
214 | ||
215 | /* | |
216 | * Create/destroy watchdog threads as CPUs come and go: | |
217 | */ | |
218 | static int __cpuinit | |
219 | cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) | |
220 | { | |
221 | int hotcpu = (unsigned long)hcpu; | |
222 | struct task_struct *p; | |
223 | ||
224 | switch (action) { | |
225 | case CPU_UP_PREPARE: | |
226 | case CPU_UP_PREPARE_FROZEN: | |
227 | BUG_ON(per_cpu(softlockup_watchdog, hotcpu)); | |
228 | p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); | |
229 | if (IS_ERR(p)) { | |
230 | printk(KERN_ERR "watchdog for %i failed\n", hotcpu); | |
231 | return NOTIFY_BAD; | |
232 | } | |
233 | per_cpu(softlockup_touch_ts, hotcpu) = 0; | |
234 | per_cpu(softlockup_watchdog, hotcpu) = p; | |
235 | kthread_bind(p, hotcpu); | |
236 | break; | |
237 | case CPU_ONLINE: | |
238 | case CPU_ONLINE_FROZEN: | |
239 | wake_up_process(per_cpu(softlockup_watchdog, hotcpu)); | |
240 | break; | |
241 | #ifdef CONFIG_HOTPLUG_CPU | |
242 | case CPU_UP_CANCELED: | |
243 | case CPU_UP_CANCELED_FROZEN: | |
244 | if (!per_cpu(softlockup_watchdog, hotcpu)) | |
245 | break; | |
246 | /* Unbind so it can run. Fall thru. */ | |
247 | kthread_bind(per_cpu(softlockup_watchdog, hotcpu), | |
248 | cpumask_any(cpu_online_mask)); | |
249 | case CPU_DEAD: | |
250 | case CPU_DEAD_FROZEN: | |
251 | p = per_cpu(softlockup_watchdog, hotcpu); | |
252 | per_cpu(softlockup_watchdog, hotcpu) = NULL; | |
253 | kthread_stop(p); | |
254 | break; | |
255 | #endif /* CONFIG_HOTPLUG_CPU */ | |
256 | } | |
257 | return NOTIFY_OK; | |
258 | } | |
259 | ||
260 | static struct notifier_block __cpuinitdata cpu_nfb = { | |
261 | .notifier_call = cpu_callback | |
262 | }; | |
263 | ||
264 | static int __initdata nosoftlockup; | |
265 | ||
266 | static int __init nosoftlockup_setup(char *str) | |
267 | { | |
268 | nosoftlockup = 1; | |
269 | return 1; | |
270 | } | |
271 | __setup("nosoftlockup", nosoftlockup_setup); | |
272 | ||
273 | static int __init spawn_softlockup_task(void) | |
274 | { | |
275 | void *cpu = (void *)(long)smp_processor_id(); | |
276 | int err; | |
277 | ||
278 | if (nosoftlockup) | |
279 | return 0; | |
280 | ||
281 | err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); | |
282 | if (err == NOTIFY_BAD) { | |
283 | BUG(); | |
284 | return 1; | |
285 | } | |
286 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); | |
287 | register_cpu_notifier(&cpu_nfb); | |
288 | ||
289 | atomic_notifier_chain_register(&panic_notifier_list, &panic_block); | |
290 | ||
291 | return 0; | |
292 | } | |
293 | early_initcall(spawn_softlockup_task); |