packaging: Add spec file for VisionFive
[platform/kernel/linux-starfive.git] / kernel / hung_task.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Detect Hung Task
4  *
5  * kernel/hung_task.c - kernel thread for detecting tasks stuck in D state
6  *
7  */
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/export.h>
18 #include <linux/panic_notifier.h>
19 #include <linux/sysctl.h>
20 #include <linux/suspend.h>
21 #include <linux/utsname.h>
22 #include <linux/sched/signal.h>
23 #include <linux/sched/debug.h>
24 #include <linux/sched/sysctl.h>
25
26 #include <trace/events/sched.h>
27
28 /*
29  * The number of tasks checked:
30  */
31 int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
32
33 /*
34  * Limit number of tasks checked in a batch.
35  *
36  * This value controls the preemptibility of khungtaskd since preemption
37  * is disabled during the critical section. It also controls the size of
38  * the RCU grace period. So it needs to be upper-bound.
39  */
40 #define HUNG_TASK_LOCK_BREAK (HZ / 10)
41
42 /*
43  * Zero means infinite timeout - no checking done:
44  */
45 unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;
46
47 /*
48  * Zero (default value) means use sysctl_hung_task_timeout_secs:
49  */
50 unsigned long __read_mostly sysctl_hung_task_check_interval_secs;
51
52 int __read_mostly sysctl_hung_task_warnings = 10;
53
54 static int __read_mostly did_panic;
55 static bool hung_task_show_lock;
56 static bool hung_task_call_panic;
57 static bool hung_task_show_all_bt;
58
59 static struct task_struct *watchdog_task;
60
61 #ifdef CONFIG_SMP
62 /*
63  * Should we dump all CPUs backtraces in a hung task event?
64  * Defaults to 0, can be changed via sysctl.
65  */
66 static unsigned int __read_mostly sysctl_hung_task_all_cpu_backtrace;
67 #else
68 #define sysctl_hung_task_all_cpu_backtrace 0
69 #endif /* CONFIG_SMP */
70
71 /*
72  * Should we panic (and reboot, if panic_timeout= is set) when a
73  * hung task is detected:
74  */
75 unsigned int __read_mostly sysctl_hung_task_panic =
76                                 IS_ENABLED(CONFIG_BOOTPARAM_HUNG_TASK_PANIC);
77
78 static int
79 hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
80 {
81         did_panic = 1;
82
83         return NOTIFY_DONE;
84 }
85
86 static struct notifier_block panic_block = {
87         .notifier_call = hung_task_panic,
88 };
89
90 static void check_hung_task(struct task_struct *t, unsigned long timeout)
91 {
92         unsigned long switch_count = t->nvcsw + t->nivcsw;
93
94         /*
95          * Ensure the task is not frozen.
96          * Also, skip vfork and any other user process that freezer should skip.
97          */
98         if (unlikely(READ_ONCE(t->__state) & TASK_FROZEN))
99                 return;
100
101         /*
102          * When a freshly created task is scheduled once, changes its state to
103          * TASK_UNINTERRUPTIBLE without having ever been switched out once, it
104          * musn't be checked.
105          */
106         if (unlikely(!switch_count))
107                 return;
108
109         if (switch_count != t->last_switch_count) {
110                 t->last_switch_count = switch_count;
111                 t->last_switch_time = jiffies;
112                 return;
113         }
114         if (time_is_after_jiffies(t->last_switch_time + timeout * HZ))
115                 return;
116
117         trace_sched_process_hang(t);
118
119         if (sysctl_hung_task_panic) {
120                 console_verbose();
121                 hung_task_show_lock = true;
122                 hung_task_call_panic = true;
123         }
124
125         /*
126          * Ok, the task did not get scheduled for more than 2 minutes,
127          * complain:
128          */
129         if (sysctl_hung_task_warnings) {
130                 if (sysctl_hung_task_warnings > 0)
131                         sysctl_hung_task_warnings--;
132                 pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
133                        t->comm, t->pid, (jiffies - t->last_switch_time) / HZ);
134                 pr_err("      %s %s %.*s\n",
135                         print_tainted(), init_utsname()->release,
136                         (int)strcspn(init_utsname()->version, " "),
137                         init_utsname()->version);
138                 pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
139                         " disables this message.\n");
140                 sched_show_task(t);
141                 hung_task_show_lock = true;
142
143                 if (sysctl_hung_task_all_cpu_backtrace)
144                         hung_task_show_all_bt = true;
145         }
146
147         touch_nmi_watchdog();
148 }
149
150 /*
151  * To avoid extending the RCU grace period for an unbounded amount of time,
152  * periodically exit the critical section and enter a new one.
153  *
154  * For preemptible RCU it is sufficient to call rcu_read_unlock in order
155  * to exit the grace period. For classic RCU, a reschedule is required.
156  */
157 static bool rcu_lock_break(struct task_struct *g, struct task_struct *t)
158 {
159         bool can_cont;
160
161         get_task_struct(g);
162         get_task_struct(t);
163         rcu_read_unlock();
164         cond_resched();
165         rcu_read_lock();
166         can_cont = pid_alive(g) && pid_alive(t);
167         put_task_struct(t);
168         put_task_struct(g);
169
170         return can_cont;
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(unsigned long timeout)
179 {
180         int max_count = sysctl_hung_task_check_count;
181         unsigned long last_break = jiffies;
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 (test_taint(TAINT_DIE) || did_panic)
189                 return;
190
191         hung_task_show_lock = false;
192         rcu_read_lock();
193         for_each_process_thread(g, t) {
194                 unsigned int state;
195
196                 if (!max_count--)
197                         goto unlock;
198                 if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) {
199                         if (!rcu_lock_break(g, t))
200                                 goto unlock;
201                         last_break = jiffies;
202                 }
203                 /*
204                  * skip the TASK_KILLABLE tasks -- these can be killed
205                  * skip the TASK_IDLE tasks -- those are genuinely idle
206                  */
207                 state = READ_ONCE(t->__state);
208                 if ((state & TASK_UNINTERRUPTIBLE) &&
209                     !(state & TASK_WAKEKILL) &&
210                     !(state & TASK_NOLOAD))
211                         check_hung_task(t, timeout);
212         }
213  unlock:
214         rcu_read_unlock();
215         if (hung_task_show_lock)
216                 debug_show_all_locks();
217
218         if (hung_task_show_all_bt) {
219                 hung_task_show_all_bt = false;
220                 trigger_all_cpu_backtrace();
221         }
222
223         if (hung_task_call_panic)
224                 panic("hung_task: blocked tasks");
225 }
226
227 static long hung_timeout_jiffies(unsigned long last_checked,
228                                  unsigned long timeout)
229 {
230         /* timeout of 0 will disable the watchdog */
231         return timeout ? last_checked - jiffies + timeout * HZ :
232                 MAX_SCHEDULE_TIMEOUT;
233 }
234
235 #ifdef CONFIG_SYSCTL
236 /*
237  * Process updating of timeout sysctl
238  */
239 static int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
240                                   void *buffer,
241                                   size_t *lenp, loff_t *ppos)
242 {
243         int ret;
244
245         ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
246
247         if (ret || !write)
248                 goto out;
249
250         wake_up_process(watchdog_task);
251
252  out:
253         return ret;
254 }
255
256 /*
257  * This is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs
258  * and hung_task_check_interval_secs
259  */
260 static const unsigned long hung_task_timeout_max = (LONG_MAX / HZ);
261 static struct ctl_table hung_task_sysctls[] = {
262 #ifdef CONFIG_SMP
263         {
264                 .procname       = "hung_task_all_cpu_backtrace",
265                 .data           = &sysctl_hung_task_all_cpu_backtrace,
266                 .maxlen         = sizeof(int),
267                 .mode           = 0644,
268                 .proc_handler   = proc_dointvec_minmax,
269                 .extra1         = SYSCTL_ZERO,
270                 .extra2         = SYSCTL_ONE,
271         },
272 #endif /* CONFIG_SMP */
273         {
274                 .procname       = "hung_task_panic",
275                 .data           = &sysctl_hung_task_panic,
276                 .maxlen         = sizeof(int),
277                 .mode           = 0644,
278                 .proc_handler   = proc_dointvec_minmax,
279                 .extra1         = SYSCTL_ZERO,
280                 .extra2         = SYSCTL_ONE,
281         },
282         {
283                 .procname       = "hung_task_check_count",
284                 .data           = &sysctl_hung_task_check_count,
285                 .maxlen         = sizeof(int),
286                 .mode           = 0644,
287                 .proc_handler   = proc_dointvec_minmax,
288                 .extra1         = SYSCTL_ZERO,
289         },
290         {
291                 .procname       = "hung_task_timeout_secs",
292                 .data           = &sysctl_hung_task_timeout_secs,
293                 .maxlen         = sizeof(unsigned long),
294                 .mode           = 0644,
295                 .proc_handler   = proc_dohung_task_timeout_secs,
296                 .extra2         = (void *)&hung_task_timeout_max,
297         },
298         {
299                 .procname       = "hung_task_check_interval_secs",
300                 .data           = &sysctl_hung_task_check_interval_secs,
301                 .maxlen         = sizeof(unsigned long),
302                 .mode           = 0644,
303                 .proc_handler   = proc_dohung_task_timeout_secs,
304                 .extra2         = (void *)&hung_task_timeout_max,
305         },
306         {
307                 .procname       = "hung_task_warnings",
308                 .data           = &sysctl_hung_task_warnings,
309                 .maxlen         = sizeof(int),
310                 .mode           = 0644,
311                 .proc_handler   = proc_dointvec_minmax,
312                 .extra1         = SYSCTL_NEG_ONE,
313         },
314         {}
315 };
316
317 static void __init hung_task_sysctl_init(void)
318 {
319         register_sysctl_init("kernel", hung_task_sysctls);
320 }
321 #else
322 #define hung_task_sysctl_init() do { } while (0)
323 #endif /* CONFIG_SYSCTL */
324
325
326 static atomic_t reset_hung_task = ATOMIC_INIT(0);
327
328 void reset_hung_task_detector(void)
329 {
330         atomic_set(&reset_hung_task, 1);
331 }
332 EXPORT_SYMBOL_GPL(reset_hung_task_detector);
333
334 static bool hung_detector_suspended;
335
336 static int hungtask_pm_notify(struct notifier_block *self,
337                               unsigned long action, void *hcpu)
338 {
339         switch (action) {
340         case PM_SUSPEND_PREPARE:
341         case PM_HIBERNATION_PREPARE:
342         case PM_RESTORE_PREPARE:
343                 hung_detector_suspended = true;
344                 break;
345         case PM_POST_SUSPEND:
346         case PM_POST_HIBERNATION:
347         case PM_POST_RESTORE:
348                 hung_detector_suspended = false;
349                 break;
350         default:
351                 break;
352         }
353         return NOTIFY_OK;
354 }
355
356 /*
357  * kthread which checks for tasks stuck in D state
358  */
359 static int watchdog(void *dummy)
360 {
361         unsigned long hung_last_checked = jiffies;
362
363         set_user_nice(current, 0);
364
365         for ( ; ; ) {
366                 unsigned long timeout = sysctl_hung_task_timeout_secs;
367                 unsigned long interval = sysctl_hung_task_check_interval_secs;
368                 long t;
369
370                 if (interval == 0)
371                         interval = timeout;
372                 interval = min_t(unsigned long, interval, timeout);
373                 t = hung_timeout_jiffies(hung_last_checked, interval);
374                 if (t <= 0) {
375                         if (!atomic_xchg(&reset_hung_task, 0) &&
376                             !hung_detector_suspended)
377                                 check_hung_uninterruptible_tasks(timeout);
378                         hung_last_checked = jiffies;
379                         continue;
380                 }
381                 schedule_timeout_interruptible(t);
382         }
383
384         return 0;
385 }
386
387 static int __init hung_task_init(void)
388 {
389         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
390
391         /* Disable hung task detector on suspend */
392         pm_notifier(hungtask_pm_notify, 0);
393
394         watchdog_task = kthread_run(watchdog, NULL, "khungtaskd");
395         hung_task_sysctl_init();
396
397         return 0;
398 }
399 subsys_initcall(hung_task_init);