1 files changed, 315 insertions, 0 deletions
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
new file mode 100644
index 000000000..396ebaebe
--- /dev/null
+++ b/kernel/hung_task.c
@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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/suspend.h>
+#include <linux/utsname.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/sysctl.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_LOCK_BREAK (HZ / 10)
+
+/*
+ * Zero means infinite timeout - no checking done:
+ */
+unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;
+
+/*
+ * Zero (default value) means use sysctl_hung_task_timeout_secs:
+ */
+unsigned long __read_mostly sysctl_hung_task_check_interval_secs;
+
+int __read_mostly sysctl_hung_task_warnings = 10;
+
+static int __read_mostly did_panic;
+static bool hung_task_show_lock;
+static bool hung_task_call_panic;
+static bool hung_task_show_all_bt;
+
+static struct task_struct *watchdog_task;
+
+#ifdef CONFIG_SMP
+/*
+ * Should we dump all CPUs backtraces in a hung task event?
+ * Defaults to 0, can be changed via sysctl.
+ */
+unsigned int __read_mostly sysctl_hung_task_all_cpu_backtrace;
+#endif /* CONFIG_SMP */
+
+/*
+ * 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
+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;
+		t->last_switch_time = jiffies;
+		return;
+	}
+	if (time_is_after_jiffies(t->last_switch_time + timeout * HZ))
+		return;
+
+	trace_sched_process_hang(t);
+
+	if (sysctl_hung_task_panic) {
+		console_verbose();
+		hung_task_show_lock = true;
+		hung_task_call_panic = true;
+	}
+
+	/*
+	 * 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, (jiffies - t->last_switch_time) / HZ);
+		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);
+		hung_task_show_lock = true;
+
+		if (sysctl_hung_task_all_cpu_backtrace)
+			hung_task_show_all_bt = true;
+	}
+
+	touch_nmi_watchdog();
+}
+
+/*
+ * 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;
+	unsigned long last_break = jiffies;
+	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;
+
+	hung_task_show_lock = false;
+	rcu_read_lock();
+	for_each_process_thread(g, t) {
+		if (!max_count--)
+			goto unlock;
+		if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) {
+			if (!rcu_lock_break(g, t))
+				goto unlock;
+			last_break = jiffies;
+		}
+		/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
+		if (t->state == TASK_UNINTERRUPTIBLE)
+			check_hung_task(t, timeout);
+	}
+ unlock:
+	rcu_read_unlock();
+	if (hung_task_show_lock)
+		debug_show_all_locks();
+
+	if (hung_task_show_all_bt) {
+		hung_task_show_all_bt = false;
+		trigger_all_cpu_backtrace();
+	}
+
+	if (hung_task_call_panic)
+		panic("hung_task: blocked tasks");
+}
+
+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 *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);
+
+static bool hung_detector_suspended;
+
+static int hungtask_pm_notify(struct notifier_block *self,
+			      unsigned long action, void *hcpu)
+{
+	switch (action) {
+	case PM_SUSPEND_PREPARE:
+	case PM_HIBERNATION_PREPARE:
+	case PM_RESTORE_PREPARE:
+		hung_detector_suspended = true;
+		break;
+	case PM_POST_SUSPEND:
+	case PM_POST_HIBERNATION:
+	case PM_POST_RESTORE:
+		hung_detector_suspended = false;
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+/*
+ * 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;
+		unsigned long interval = sysctl_hung_task_check_interval_secs;
+		long t;
+
+		if (interval == 0)
+			interval = timeout;
+		interval = min_t(unsigned long, interval, timeout);
+		t = hung_timeout_jiffies(hung_last_checked, interval);
+		if (t <= 0) {
+			if (!atomic_xchg(&reset_hung_task, 0) &&
+			    !hung_detector_suspended)
+				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);
+
+	/* Disable hung task detector on suspend */
+	pm_notifier(hungtask_pm_notify, 0);
+
+	watchdog_task = kthread_run(watchdog, NULL, "khungtaskd");
+
+	return 0;
+}
+subsys_initcall(hung_task_init);