| /* |
| * Detect Hung Task |
| * |
| * kernel/hung_task.c - kernel thread for detecting tasks stuck in D state |
| * |
| */ |
| |
| #include <linux/mm.h> |
| #include <linux/cpu.h> |
| #include <linux/nmi.h> |
| #include <linux/init.h> |
| #include <linux/delay.h> |
| #include <linux/freezer.h> |
| #include <linux/kthread.h> |
| #include <linux/lockdep.h> |
| #include <linux/export.h> |
| #include <linux/sysctl.h> |
| #include <linux/utsname.h> |
| #include <linux/sched/signal.h> |
| #include <linux/sched/debug.h> |
| |
| #include <trace/events/sched.h> |
| |
| /* |
| * The number of tasks checked: |
| */ |
| int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; |
| |
| /* |
| * Limit number of tasks checked in a batch. |
| * |
| * This value controls the preemptibility of khungtaskd since preemption |
| * is disabled during the critical section. It also controls the size of |
| * the RCU grace period. So it needs to be upper-bound. |
| */ |
| #define HUNG_TASK_BATCHING 1024 |
| |
| /* |
| * Zero means infinite timeout - no checking done: |
| */ |
| unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT; |
| |
| int __read_mostly sysctl_hung_task_warnings = 10; |
| |
| static int __read_mostly did_panic; |
| |
| static struct task_struct *watchdog_task; |
| |
| /* |
| * Should we panic (and reboot, if panic_timeout= is set) when a |
| * hung task is detected: |
| */ |
| unsigned int __read_mostly sysctl_hung_task_panic = |
| CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE; |
| |
| static int __init hung_task_panic_setup(char *str) |
| { |
| int rc = kstrtouint(str, 0, &sysctl_hung_task_panic); |
| |
| if (rc) |
| return rc; |
| return 1; |
| } |
| __setup("hung_task_panic=", hung_task_panic_setup); |
| |
| static int |
| hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr) |
| { |
| did_panic = 1; |
| |
| return NOTIFY_DONE; |
| } |
| |
| static struct notifier_block panic_block = { |
| .notifier_call = hung_task_panic, |
| }; |
| |
| static void check_hung_task(struct task_struct *t, unsigned long timeout) |
| { |
| unsigned long switch_count = t->nvcsw + t->nivcsw; |
| |
| /* |
| * Ensure the task is not frozen. |
| * Also, skip vfork and any other user process that freezer should skip. |
| */ |
| if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP))) |
| return; |
| |
| /* |
| * When a freshly created task is scheduled once, changes its state to |
| * TASK_UNINTERRUPTIBLE without having ever been switched out once, it |
| * musn't be checked. |
| */ |
| if (unlikely(!switch_count)) |
| return; |
| |
| if (switch_count != t->last_switch_count) { |
| t->last_switch_count = switch_count; |
| return; |
| } |
| |
| trace_sched_process_hang(t); |
| |
| if (!sysctl_hung_task_warnings && !sysctl_hung_task_panic) |
| return; |
| |
| /* |
| * Ok, the task did not get scheduled for more than 2 minutes, |
| * complain: |
| */ |
| if (sysctl_hung_task_warnings) { |
| if (sysctl_hung_task_warnings > 0) |
| sysctl_hung_task_warnings--; |
| pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", |
| t->comm, t->pid, timeout); |
| pr_err(" %s %s %.*s\n", |
| print_tainted(), init_utsname()->release, |
| (int)strcspn(init_utsname()->version, " "), |
| init_utsname()->version); |
| pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" |
| " disables this message.\n"); |
| sched_show_task(t); |
| debug_show_all_locks(); |
| } |
| |
| touch_nmi_watchdog(); |
| |
| if (sysctl_hung_task_panic) { |
| trigger_all_cpu_backtrace(); |
| panic("hung_task: blocked tasks"); |
| } |
| } |
| |
| /* |
| * To avoid extending the RCU grace period for an unbounded amount of time, |
| * periodically exit the critical section and enter a new one. |
| * |
| * For preemptible RCU it is sufficient to call rcu_read_unlock in order |
| * to exit the grace period. For classic RCU, a reschedule is required. |
| */ |
| static bool rcu_lock_break(struct task_struct *g, struct task_struct *t) |
| { |
| bool can_cont; |
| |
| get_task_struct(g); |
| get_task_struct(t); |
| rcu_read_unlock(); |
| cond_resched(); |
| rcu_read_lock(); |
| can_cont = pid_alive(g) && pid_alive(t); |
| put_task_struct(t); |
| put_task_struct(g); |
| |
| return can_cont; |
| } |
| |
| /* |
| * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for |
| * a really long time (120 seconds). If that happens, print out |
| * a warning. |
| */ |
| static void check_hung_uninterruptible_tasks(unsigned long timeout) |
| { |
| int max_count = sysctl_hung_task_check_count; |
| int batch_count = HUNG_TASK_BATCHING; |
| struct task_struct *g, *t; |
| |
| /* |
| * If the system crashed already then all bets are off, |
| * do not report extra hung tasks: |
| */ |
| if (test_taint(TAINT_DIE) || did_panic) |
| return; |
| |
| rcu_read_lock(); |
| for_each_process_thread(g, t) { |
| if (!max_count--) |
| goto unlock; |
| if (!--batch_count) { |
| batch_count = HUNG_TASK_BATCHING; |
| if (!rcu_lock_break(g, t)) |
| goto unlock; |
| } |
| /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */ |
| if (t->state == TASK_UNINTERRUPTIBLE) |
| check_hung_task(t, timeout); |
| } |
| unlock: |
| rcu_read_unlock(); |
| } |
| |
| static long hung_timeout_jiffies(unsigned long last_checked, |
| unsigned long timeout) |
| { |
| /* timeout of 0 will disable the watchdog */ |
| return timeout ? last_checked - jiffies + timeout * HZ : |
| MAX_SCHEDULE_TIMEOUT; |
| } |
| |
| /* |
| * Process updating of timeout sysctl |
| */ |
| int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, |
| void __user *buffer, |
| size_t *lenp, loff_t *ppos) |
| { |
| int ret; |
| |
| ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
| |
| if (ret || !write) |
| goto out; |
| |
| wake_up_process(watchdog_task); |
| |
| out: |
| return ret; |
| } |
| |
| static atomic_t reset_hung_task = ATOMIC_INIT(0); |
| |
| void reset_hung_task_detector(void) |
| { |
| atomic_set(&reset_hung_task, 1); |
| } |
| EXPORT_SYMBOL_GPL(reset_hung_task_detector); |
| |
| /* |
| * kthread which checks for tasks stuck in D state |
| */ |
| static int watchdog(void *dummy) |
| { |
| unsigned long hung_last_checked = jiffies; |
| |
| set_user_nice(current, 0); |
| |
| for ( ; ; ) { |
| unsigned long timeout = sysctl_hung_task_timeout_secs; |
| long t = hung_timeout_jiffies(hung_last_checked, timeout); |
| |
| if (t <= 0) { |
| if (!atomic_xchg(&reset_hung_task, 0)) |
| check_hung_uninterruptible_tasks(timeout); |
| hung_last_checked = jiffies; |
| continue; |
| } |
| schedule_timeout_interruptible(t); |
| } |
| |
| return 0; |
| } |
| |
| static int __init hung_task_init(void) |
| { |
| atomic_notifier_chain_register(&panic_notifier_list, &panic_block); |
| watchdog_task = kthread_run(watchdog, NULL, "khungtaskd"); |
| |
| return 0; |
| } |
| subsys_initcall(hung_task_init); |