--- /dev/null
+/*
+ * 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 <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)
+ return;
+
+ if (sysctl_hung_task_warnings > 0)
+ sysctl_hung_task_warnings--;
+
+ /*
+ * Ok, the task did not get scheduled for more than 2 minutes,
+ * complain:
+ */
+ 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_held_locks(t);
+
+ 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 unsigned long timeout_jiffies(unsigned long timeout)
+{
+ /* timeout of 0 will disable the watchdog */
+ return timeout ? 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)
+{
+ set_user_nice(current, 0);
+
+ for ( ; ; ) {
+ unsigned long timeout = sysctl_hung_task_timeout_secs;
+
+ while (schedule_timeout_interruptible(timeout_jiffies(timeout)))
+ timeout = sysctl_hung_task_timeout_secs;
+
+ if (atomic_xchg(&reset_hung_task, 0))
+ continue;
+
+ check_hung_uninterruptible_tasks(timeout);
+ }
+
+ 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);
Code Review / kvmfornfv.git / blobdiff