Commit | Line | Data |
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8446f1d3 IM |
1 | /* |
2 | * Detect Soft Lockups | |
3 | * | |
6687a97d | 4 | * started by Ingo Molnar, Copyright (C) 2005, 2006 Red Hat, Inc. |
8446f1d3 IM |
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 | */ | |
8446f1d3 IM |
9 | #include <linux/mm.h> |
10 | #include <linux/cpu.h> | |
82a1fcb9 | 11 | #include <linux/nmi.h> |
8446f1d3 IM |
12 | #include <linux/init.h> |
13 | #include <linux/delay.h> | |
83144186 | 14 | #include <linux/freezer.h> |
8446f1d3 IM |
15 | #include <linux/kthread.h> |
16 | #include <linux/notifier.h> | |
17 | #include <linux/module.h> | |
18 | ||
43581a10 IM |
19 | #include <asm/irq_regs.h> |
20 | ||
8446f1d3 IM |
21 | static DEFINE_SPINLOCK(print_lock); |
22 | ||
6687a97d IM |
23 | static DEFINE_PER_CPU(unsigned long, touch_timestamp); |
24 | static DEFINE_PER_CPU(unsigned long, print_timestamp); | |
8446f1d3 IM |
25 | static DEFINE_PER_CPU(struct task_struct *, watchdog_task); |
26 | ||
90739081 IM |
27 | static int __read_mostly did_panic; |
28 | unsigned long __read_mostly softlockup_thresh = 60; | |
6687a97d IM |
29 | |
30 | static int | |
31 | softlock_panic(struct notifier_block *this, unsigned long event, void *ptr) | |
8446f1d3 IM |
32 | { |
33 | did_panic = 1; | |
34 | ||
35 | return NOTIFY_DONE; | |
36 | } | |
37 | ||
38 | static struct notifier_block panic_block = { | |
39 | .notifier_call = softlock_panic, | |
40 | }; | |
41 | ||
966812dc JF |
42 | /* |
43 | * Returns seconds, approximately. We don't need nanosecond | |
44 | * resolution, and we don't need to waste time with a big divide when | |
45 | * 2^30ns == 1.074s. | |
46 | */ | |
a3b13c23 | 47 | static unsigned long get_timestamp(int this_cpu) |
966812dc | 48 | { |
82a1fcb9 | 49 | return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ |
966812dc JF |
50 | } |
51 | ||
8446f1d3 IM |
52 | void touch_softlockup_watchdog(void) |
53 | { | |
a3b13c23 IM |
54 | int this_cpu = raw_smp_processor_id(); |
55 | ||
56 | __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu); | |
8446f1d3 IM |
57 | } |
58 | EXPORT_SYMBOL(touch_softlockup_watchdog); | |
59 | ||
04c9167f JF |
60 | void touch_all_softlockup_watchdogs(void) |
61 | { | |
62 | int cpu; | |
63 | ||
64 | /* Cause each CPU to re-update its timestamp rather than complain */ | |
65 | for_each_online_cpu(cpu) | |
66 | per_cpu(touch_timestamp, cpu) = 0; | |
67 | } | |
68 | EXPORT_SYMBOL(touch_all_softlockup_watchdogs); | |
69 | ||
8446f1d3 IM |
70 | /* |
71 | * This callback runs from the timer interrupt, and checks | |
72 | * whether the watchdog thread has hung or not: | |
73 | */ | |
6687a97d | 74 | void softlockup_tick(void) |
8446f1d3 IM |
75 | { |
76 | int this_cpu = smp_processor_id(); | |
6687a97d | 77 | unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu); |
966812dc | 78 | unsigned long print_timestamp; |
43581a10 | 79 | struct pt_regs *regs = get_irq_regs(); |
966812dc | 80 | unsigned long now; |
8446f1d3 | 81 | |
04c9167f JF |
82 | if (touch_timestamp == 0) { |
83 | touch_softlockup_watchdog(); | |
966812dc | 84 | return; |
04c9167f | 85 | } |
966812dc JF |
86 | |
87 | print_timestamp = per_cpu(print_timestamp, this_cpu); | |
88 | ||
89 | /* report at most once a second */ | |
a115d5ca IM |
90 | if ((print_timestamp >= touch_timestamp && |
91 | print_timestamp < (touch_timestamp + 1)) || | |
92 | did_panic || !per_cpu(watchdog_task, this_cpu)) { | |
8446f1d3 | 93 | return; |
a115d5ca | 94 | } |
8446f1d3 | 95 | |
6687a97d IM |
96 | /* do not print during early bootup: */ |
97 | if (unlikely(system_state != SYSTEM_RUNNING)) { | |
98 | touch_softlockup_watchdog(); | |
8446f1d3 | 99 | return; |
6687a97d | 100 | } |
8446f1d3 | 101 | |
a3b13c23 | 102 | now = get_timestamp(this_cpu); |
966812dc | 103 | |
82a1fcb9 | 104 | /* Warn about unreasonable delays: */ |
c4f3b63f | 105 | if (now <= (touch_timestamp + softlockup_thresh)) |
43581a10 | 106 | return; |
8446f1d3 | 107 | |
43581a10 IM |
108 | per_cpu(print_timestamp, this_cpu) = touch_timestamp; |
109 | ||
110 | spin_lock(&print_lock); | |
c4f3b63f RT |
111 | printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n", |
112 | this_cpu, now - touch_timestamp, | |
ba25f9dc | 113 | current->comm, task_pid_nr(current)); |
43581a10 IM |
114 | if (regs) |
115 | show_regs(regs); | |
116 | else | |
6687a97d | 117 | dump_stack(); |
43581a10 | 118 | spin_unlock(&print_lock); |
8446f1d3 IM |
119 | } |
120 | ||
82a1fcb9 IM |
121 | /* |
122 | * Have a reasonable limit on the number of tasks checked: | |
123 | */ | |
90739081 | 124 | unsigned long __read_mostly sysctl_hung_task_check_count = 1024; |
82a1fcb9 IM |
125 | |
126 | /* | |
127 | * Zero means infinite timeout - no checking done: | |
128 | */ | |
90739081 | 129 | unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120; |
82a1fcb9 | 130 | |
90739081 | 131 | unsigned long __read_mostly sysctl_hung_task_warnings = 10; |
82a1fcb9 IM |
132 | |
133 | /* | |
134 | * Only do the hung-tasks check on one CPU: | |
135 | */ | |
136 | static int check_cpu __read_mostly = -1; | |
137 | ||
138 | static void check_hung_task(struct task_struct *t, unsigned long now) | |
139 | { | |
140 | unsigned long switch_count = t->nvcsw + t->nivcsw; | |
141 | ||
142 | if (t->flags & PF_FROZEN) | |
143 | return; | |
144 | ||
145 | if (switch_count != t->last_switch_count || !t->last_switch_timestamp) { | |
146 | t->last_switch_count = switch_count; | |
147 | t->last_switch_timestamp = now; | |
148 | return; | |
149 | } | |
150 | if ((long)(now - t->last_switch_timestamp) < | |
151 | sysctl_hung_task_timeout_secs) | |
152 | return; | |
153 | if (sysctl_hung_task_warnings < 0) | |
154 | return; | |
155 | sysctl_hung_task_warnings--; | |
156 | ||
157 | /* | |
158 | * Ok, the task did not get scheduled for more than 2 minutes, | |
159 | * complain: | |
160 | */ | |
161 | printk(KERN_ERR "INFO: task %s:%d blocked for more than " | |
162 | "%ld seconds.\n", t->comm, t->pid, | |
163 | sysctl_hung_task_timeout_secs); | |
164 | printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" | |
165 | " disables this message.\n"); | |
166 | sched_show_task(t); | |
167 | __debug_show_held_locks(t); | |
168 | ||
169 | t->last_switch_timestamp = now; | |
170 | touch_nmi_watchdog(); | |
171 | } | |
172 | ||
173 | /* | |
174 | * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for | |
175 | * a really long time (120 seconds). If that happens, print out | |
176 | * a warning. | |
177 | */ | |
178 | static void check_hung_uninterruptible_tasks(int this_cpu) | |
179 | { | |
180 | int max_count = sysctl_hung_task_check_count; | |
181 | unsigned long now = get_timestamp(this_cpu); | |
182 | struct task_struct *g, *t; | |
183 | ||
184 | /* | |
185 | * If the system crashed already then all bets are off, | |
186 | * do not report extra hung tasks: | |
187 | */ | |
188 | if ((tainted & TAINT_DIE) || did_panic) | |
189 | return; | |
190 | ||
191 | read_lock(&tasklist_lock); | |
192 | do_each_thread(g, t) { | |
193 | if (!--max_count) | |
194 | break; | |
195 | if (t->state & TASK_UNINTERRUPTIBLE) | |
196 | check_hung_task(t, now); | |
197 | } while_each_thread(g, t); | |
198 | ||
199 | read_unlock(&tasklist_lock); | |
200 | } | |
201 | ||
8446f1d3 IM |
202 | /* |
203 | * The watchdog thread - runs every second and touches the timestamp. | |
204 | */ | |
a5f2ce3c | 205 | static int watchdog(void *__bind_cpu) |
8446f1d3 | 206 | { |
02fb6149 | 207 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |
82a1fcb9 | 208 | int this_cpu = (long)__bind_cpu; |
8446f1d3 IM |
209 | |
210 | sched_setscheduler(current, SCHED_FIFO, ¶m); | |
8446f1d3 | 211 | |
966812dc JF |
212 | /* initialize timestamp */ |
213 | touch_softlockup_watchdog(); | |
214 | ||
8446f1d3 | 215 | /* |
6687a97d | 216 | * Run briefly once per second to reset the softlockup timestamp. |
82a1fcb9 | 217 | * If this gets delayed for more than 60 seconds then the |
6687a97d | 218 | * debug-printout triggers in softlockup_tick(). |
8446f1d3 IM |
219 | */ |
220 | while (!kthread_should_stop()) { | |
8446f1d3 | 221 | touch_softlockup_watchdog(); |
82a1fcb9 IM |
222 | msleep_interruptible(10000); |
223 | ||
224 | if (this_cpu != check_cpu) | |
225 | continue; | |
226 | ||
227 | if (sysctl_hung_task_timeout_secs) | |
228 | check_hung_uninterruptible_tasks(this_cpu); | |
8446f1d3 | 229 | } |
8446f1d3 IM |
230 | |
231 | return 0; | |
232 | } | |
233 | ||
234 | /* | |
235 | * Create/destroy watchdog threads as CPUs come and go: | |
236 | */ | |
8c78f307 | 237 | static int __cpuinit |
8446f1d3 IM |
238 | cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) |
239 | { | |
240 | int hotcpu = (unsigned long)hcpu; | |
241 | struct task_struct *p; | |
242 | ||
243 | switch (action) { | |
244 | case CPU_UP_PREPARE: | |
8bb78442 | 245 | case CPU_UP_PREPARE_FROZEN: |
8446f1d3 IM |
246 | BUG_ON(per_cpu(watchdog_task, hotcpu)); |
247 | p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); | |
248 | if (IS_ERR(p)) { | |
a5f2ce3c | 249 | printk(KERN_ERR "watchdog for %i failed\n", hotcpu); |
8446f1d3 IM |
250 | return NOTIFY_BAD; |
251 | } | |
a5f2ce3c IM |
252 | per_cpu(touch_timestamp, hotcpu) = 0; |
253 | per_cpu(watchdog_task, hotcpu) = p; | |
8446f1d3 | 254 | kthread_bind(p, hotcpu); |
a5f2ce3c | 255 | break; |
8446f1d3 | 256 | case CPU_ONLINE: |
8bb78442 | 257 | case CPU_ONLINE_FROZEN: |
82a1fcb9 | 258 | check_cpu = any_online_cpu(cpu_online_map); |
8446f1d3 IM |
259 | wake_up_process(per_cpu(watchdog_task, hotcpu)); |
260 | break; | |
261 | #ifdef CONFIG_HOTPLUG_CPU | |
262 | case CPU_UP_CANCELED: | |
8bb78442 | 263 | case CPU_UP_CANCELED_FROZEN: |
fc75cdfa HC |
264 | if (!per_cpu(watchdog_task, hotcpu)) |
265 | break; | |
8446f1d3 | 266 | /* Unbind so it can run. Fall thru. */ |
a4c4af7c HC |
267 | kthread_bind(per_cpu(watchdog_task, hotcpu), |
268 | any_online_cpu(cpu_online_map)); | |
82a1fcb9 IM |
269 | case CPU_DOWN_PREPARE: |
270 | case CPU_DOWN_PREPARE_FROZEN: | |
271 | if (hotcpu == check_cpu) { | |
272 | cpumask_t temp_cpu_online_map = cpu_online_map; | |
273 | ||
274 | cpu_clear(hotcpu, temp_cpu_online_map); | |
275 | check_cpu = any_online_cpu(temp_cpu_online_map); | |
276 | } | |
277 | break; | |
8446f1d3 | 278 | case CPU_DEAD: |
8bb78442 | 279 | case CPU_DEAD_FROZEN: |
8446f1d3 IM |
280 | p = per_cpu(watchdog_task, hotcpu); |
281 | per_cpu(watchdog_task, hotcpu) = NULL; | |
282 | kthread_stop(p); | |
283 | break; | |
284 | #endif /* CONFIG_HOTPLUG_CPU */ | |
a5f2ce3c | 285 | } |
8446f1d3 IM |
286 | return NOTIFY_OK; |
287 | } | |
288 | ||
8c78f307 | 289 | static struct notifier_block __cpuinitdata cpu_nfb = { |
8446f1d3 IM |
290 | .notifier_call = cpu_callback |
291 | }; | |
292 | ||
293 | __init void spawn_softlockup_task(void) | |
294 | { | |
295 | void *cpu = (void *)(long)smp_processor_id(); | |
07dccf33 | 296 | int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); |
8446f1d3 | 297 | |
07dccf33 | 298 | BUG_ON(err == NOTIFY_BAD); |
8446f1d3 IM |
299 | cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); |
300 | register_cpu_notifier(&cpu_nfb); | |
301 | ||
e041c683 | 302 | atomic_notifier_chain_register(&panic_notifier_list, &panic_block); |
8446f1d3 | 303 | } |