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316 lines
7.5 KiB
316 lines
7.5 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Detect Hung Task |
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* |
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* kernel/hung_task.c - kernel thread for detecting tasks stuck in D state |
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* |
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*/ |
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#include <linux/mm.h> |
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#include <linux/cpu.h> |
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#include <linux/nmi.h> |
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#include <linux/init.h> |
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#include <linux/delay.h> |
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#include <linux/freezer.h> |
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#include <linux/kthread.h> |
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#include <linux/lockdep.h> |
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#include <linux/export.h> |
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#include <linux/panic_notifier.h> |
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#include <linux/sysctl.h> |
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#include <linux/suspend.h> |
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#include <linux/utsname.h> |
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#include <linux/sched/signal.h> |
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#include <linux/sched/debug.h> |
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#include <linux/sched/sysctl.h> |
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#include <trace/events/sched.h> |
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/* |
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* The number of tasks checked: |
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*/ |
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int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; |
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/* |
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* Limit number of tasks checked in a batch. |
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* |
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* This value controls the preemptibility of khungtaskd since preemption |
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* is disabled during the critical section. It also controls the size of |
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* the RCU grace period. So it needs to be upper-bound. |
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*/ |
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#define HUNG_TASK_LOCK_BREAK (HZ / 10) |
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/* |
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* Zero means infinite timeout - no checking done: |
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*/ |
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unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT; |
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/* |
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* Zero (default value) means use sysctl_hung_task_timeout_secs: |
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*/ |
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unsigned long __read_mostly sysctl_hung_task_check_interval_secs; |
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int __read_mostly sysctl_hung_task_warnings = 10; |
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static int __read_mostly did_panic; |
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static bool hung_task_show_lock; |
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static bool hung_task_call_panic; |
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static bool hung_task_show_all_bt; |
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static struct task_struct *watchdog_task; |
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#ifdef CONFIG_SMP |
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/* |
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* Should we dump all CPUs backtraces in a hung task event? |
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* Defaults to 0, can be changed via sysctl. |
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*/ |
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unsigned int __read_mostly sysctl_hung_task_all_cpu_backtrace; |
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#endif /* CONFIG_SMP */ |
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/* |
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* Should we panic (and reboot, if panic_timeout= is set) when a |
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* hung task is detected: |
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*/ |
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unsigned int __read_mostly sysctl_hung_task_panic = |
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CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE; |
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static int |
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hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr) |
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{ |
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did_panic = 1; |
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return NOTIFY_DONE; |
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} |
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static struct notifier_block panic_block = { |
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.notifier_call = hung_task_panic, |
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}; |
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static void check_hung_task(struct task_struct *t, unsigned long timeout) |
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{ |
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unsigned long switch_count = t->nvcsw + t->nivcsw; |
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/* |
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* Ensure the task is not frozen. |
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* Also, skip vfork and any other user process that freezer should skip. |
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*/ |
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if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP))) |
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return; |
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/* |
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* When a freshly created task is scheduled once, changes its state to |
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* TASK_UNINTERRUPTIBLE without having ever been switched out once, it |
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* musn't be checked. |
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*/ |
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if (unlikely(!switch_count)) |
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return; |
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if (switch_count != t->last_switch_count) { |
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t->last_switch_count = switch_count; |
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t->last_switch_time = jiffies; |
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return; |
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} |
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if (time_is_after_jiffies(t->last_switch_time + timeout * HZ)) |
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return; |
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trace_sched_process_hang(t); |
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if (sysctl_hung_task_panic) { |
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console_verbose(); |
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hung_task_show_lock = true; |
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hung_task_call_panic = true; |
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} |
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/* |
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* Ok, the task did not get scheduled for more than 2 minutes, |
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* complain: |
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*/ |
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if (sysctl_hung_task_warnings) { |
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if (sysctl_hung_task_warnings > 0) |
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sysctl_hung_task_warnings--; |
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pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", |
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t->comm, t->pid, (jiffies - t->last_switch_time) / HZ); |
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pr_err(" %s %s %.*s\n", |
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print_tainted(), init_utsname()->release, |
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(int)strcspn(init_utsname()->version, " "), |
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init_utsname()->version); |
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pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" |
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" disables this message.\n"); |
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sched_show_task(t); |
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hung_task_show_lock = true; |
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if (sysctl_hung_task_all_cpu_backtrace) |
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hung_task_show_all_bt = true; |
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} |
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touch_nmi_watchdog(); |
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} |
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/* |
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* To avoid extending the RCU grace period for an unbounded amount of time, |
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* periodically exit the critical section and enter a new one. |
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* |
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* For preemptible RCU it is sufficient to call rcu_read_unlock in order |
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* to exit the grace period. For classic RCU, a reschedule is required. |
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*/ |
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static bool rcu_lock_break(struct task_struct *g, struct task_struct *t) |
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{ |
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bool can_cont; |
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get_task_struct(g); |
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get_task_struct(t); |
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rcu_read_unlock(); |
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cond_resched(); |
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rcu_read_lock(); |
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can_cont = pid_alive(g) && pid_alive(t); |
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put_task_struct(t); |
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put_task_struct(g); |
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return can_cont; |
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} |
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/* |
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* Check whether a TASK_UNINTERRUPTIBLE does not get woken up for |
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* a really long time (120 seconds). If that happens, print out |
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* a warning. |
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*/ |
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static void check_hung_uninterruptible_tasks(unsigned long timeout) |
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{ |
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int max_count = sysctl_hung_task_check_count; |
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unsigned long last_break = jiffies; |
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struct task_struct *g, *t; |
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/* |
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* If the system crashed already then all bets are off, |
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* do not report extra hung tasks: |
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*/ |
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if (test_taint(TAINT_DIE) || did_panic) |
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return; |
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hung_task_show_lock = false; |
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rcu_read_lock(); |
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for_each_process_thread(g, t) { |
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if (!max_count--) |
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goto unlock; |
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if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) { |
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if (!rcu_lock_break(g, t)) |
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goto unlock; |
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last_break = jiffies; |
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} |
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/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */ |
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if (READ_ONCE(t->__state) == TASK_UNINTERRUPTIBLE) |
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check_hung_task(t, timeout); |
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} |
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unlock: |
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rcu_read_unlock(); |
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if (hung_task_show_lock) |
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debug_show_all_locks(); |
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if (hung_task_show_all_bt) { |
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hung_task_show_all_bt = false; |
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trigger_all_cpu_backtrace(); |
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} |
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if (hung_task_call_panic) |
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panic("hung_task: blocked tasks"); |
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} |
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static long hung_timeout_jiffies(unsigned long last_checked, |
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unsigned long timeout) |
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{ |
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/* timeout of 0 will disable the watchdog */ |
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return timeout ? last_checked - jiffies + timeout * HZ : |
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MAX_SCHEDULE_TIMEOUT; |
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} |
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/* |
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* Process updating of timeout sysctl |
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*/ |
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int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, |
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void *buffer, size_t *lenp, loff_t *ppos) |
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{ |
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int ret; |
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ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
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if (ret || !write) |
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goto out; |
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wake_up_process(watchdog_task); |
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out: |
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return ret; |
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} |
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static atomic_t reset_hung_task = ATOMIC_INIT(0); |
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void reset_hung_task_detector(void) |
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{ |
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atomic_set(&reset_hung_task, 1); |
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} |
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EXPORT_SYMBOL_GPL(reset_hung_task_detector); |
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static bool hung_detector_suspended; |
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static int hungtask_pm_notify(struct notifier_block *self, |
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unsigned long action, void *hcpu) |
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{ |
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switch (action) { |
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case PM_SUSPEND_PREPARE: |
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case PM_HIBERNATION_PREPARE: |
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case PM_RESTORE_PREPARE: |
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hung_detector_suspended = true; |
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break; |
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case PM_POST_SUSPEND: |
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case PM_POST_HIBERNATION: |
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case PM_POST_RESTORE: |
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hung_detector_suspended = false; |
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break; |
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default: |
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break; |
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} |
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return NOTIFY_OK; |
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} |
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/* |
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* kthread which checks for tasks stuck in D state |
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*/ |
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static int watchdog(void *dummy) |
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{ |
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unsigned long hung_last_checked = jiffies; |
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set_user_nice(current, 0); |
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for ( ; ; ) { |
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unsigned long timeout = sysctl_hung_task_timeout_secs; |
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unsigned long interval = sysctl_hung_task_check_interval_secs; |
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long t; |
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if (interval == 0) |
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interval = timeout; |
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interval = min_t(unsigned long, interval, timeout); |
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t = hung_timeout_jiffies(hung_last_checked, interval); |
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if (t <= 0) { |
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if (!atomic_xchg(&reset_hung_task, 0) && |
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!hung_detector_suspended) |
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check_hung_uninterruptible_tasks(timeout); |
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hung_last_checked = jiffies; |
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continue; |
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} |
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schedule_timeout_interruptible(t); |
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} |
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return 0; |
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} |
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static int __init hung_task_init(void) |
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{ |
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atomic_notifier_chain_register(&panic_notifier_list, &panic_block); |
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/* Disable hung task detector on suspend */ |
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pm_notifier(hungtask_pm_notify, 0); |
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watchdog_task = kthread_run(watchdog, NULL, "khungtaskd"); |
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return 0; |
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} |
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subsys_initcall(hung_task_init);
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