1 // SPDX-License-Identifier: GPL-2.0-only
5  * kernel/hung_task.c - kernel thread for detecting tasks stuck in D state
37  * Total number of tasks detected as hung since boot:
46  * the RCU grace period. So it needs to be upper-bound.
51  * Zero means infinite timeout - no checking done:
103 static bool task_is_hung(struct task_struct *t, unsigned long timeout)  in task_is_hung()  argument
105 	unsigned long switch_count = t->nvcsw + t->nivcsw;  in task_is_hung()
106 	unsigned int state = READ_ONCE(t->__state);  in task_is_hung()
109 	 * skip the TASK_KILLABLE tasks -- these can be killed  in task_is_hung()
110 	 * skip the TASK_IDLE tasks -- those are genuinely idle  in task_is_hung()
111 	 * skip the TASK_FROZEN task -- it reasonably stops scheduling by freezer  in task_is_hung()
125 	if (switch_count != t->last_switch_count) {  in task_is_hung()
126 		t->last_switch_count = switch_count;  in task_is_hung()
127 		t->last_switch_time = jiffies;  in task_is_hung()
130 	if (time_is_after_jiffies(t->last_switch_time + timeout * HZ))  in task_is_hung()
137 static void debug_show_blocker(struct task_struct *task, unsigned long timeout)  in debug_show_blocker()  argument
145 	blocker = READ_ONCE(task->blocker);  in debug_show_blocker()
178 			       task->comm, task->pid);  in debug_show_blocker()
182 			       task->comm, task->pid);  in debug_show_blocker()
186 			pr_err("INFO: task %s:%d is blocked on an rw-semaphore, but the owner is not found.\n",  in debug_show_blocker()
187 			       task->comm, task->pid);  in debug_show_blocker()
201 			       task->comm, task->pid, t->comm, t->pid);  in debug_show_blocker()
205 			       task->comm, task->pid, t->comm, t->pid);  in debug_show_blocker()
209 			pr_err("INFO: task %s:%d <%s> blocked on an rw-semaphore likely owned by task %s:%d <%s>\n",  in debug_show_blocker()
210 			       task->comm, task->pid, rwsem_blocked_as, t->comm,  in debug_show_blocker()
211 			       t->pid, rwsem_blocked_by);  in debug_show_blocker()
215 		if (!task_is_hung(t, timeout))  in debug_show_blocker()
221 static inline void debug_show_blocker(struct task_struct *task, unsigned long timeout)  in debug_show_blocker()  argument
226 static void check_hung_task(struct task_struct *t, unsigned long timeout,  in check_hung_task()  argument
231 	if (!task_is_hung(t, timeout))  in check_hung_task()
235 	 * This counter tracks the total number of tasks detected as hung  in check_hung_task()
240 	total_hung_task = sysctl_hung_task_detect_count - prev_detect_count;  in check_hung_task()
254 			sysctl_hung_task_warnings--;  in check_hung_task()
256 		       t->comm, t->pid, (jiffies - t->last_switch_time) / HZ);  in check_hung_task()
258 			print_tainted(), init_utsname()->release,  in check_hung_task()
259 			(int)strcspn(init_utsname()->version, " "),  in check_hung_task()
260 			init_utsname()->version);  in check_hung_task()
261 		if (t->flags & PF_POSTCOREDUMP)  in check_hung_task()
266 		debug_show_blocker(t, timeout);  in check_hung_task()
303 static void check_hung_uninterruptible_tasks(unsigned long timeout)  in check_hung_uninterruptible_tasks()  argument
323 		if (!max_count--)  in check_hung_uninterruptible_tasks()
331 		check_hung_task(t, timeout, prev_detect_count);  in check_hung_uninterruptible_tasks()
336 	if (!(sysctl_hung_task_detect_count - prev_detect_count))  in check_hung_uninterruptible_tasks()
353 				 unsigned long timeout)  in hung_timeout_jiffies()  argument
355 	/* timeout of 0 will disable the watchdog */  in hung_timeout_jiffies()
356 	return timeout ? last_checked - jiffies + timeout * HZ :  in hung_timeout_jiffies()
362  * Process updating of timeout sysctl
504 		unsigned long timeout = sysctl_hung_task_timeout_secs;  in watchdog()  local
509 			interval = timeout;  in watchdog()
510 		interval = min_t(unsigned long, interval, timeout);  in watchdog()
515 				check_hung_uninterruptible_tasks(timeout);  in watchdog()