softlockup: fix potential race in hung_task when resetting timeout

	return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */

}

static void check_hung_task(struct task_struct *t, unsigned long now)

static void check_hung_task(struct task_struct *t, unsigned long now,

			    unsigned long timeout)

{

	unsigned long switch_count = t->nvcsw + t->nivcsw;

		t->last_switch_timestamp = now;

		return;

	}

	if ((long)(now - t->last_switch_timestamp) <

					sysctl_hung_task_timeout_secs)

	if ((long)(now - t->last_switch_timestamp) < timeout)

		return;

	if (!sysctl_hung_task_warnings)

		return;

	 * complain:

	 */

	printk(KERN_ERR "INFO: task %s:%d blocked for more than "

			"%ld seconds.\n", t->comm, t->pid,

			sysctl_hung_task_timeout_secs);

			"%ld seconds.\n", t->comm, t->pid, timeout);

	printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""

			" disables this message.\n");

	sched_show_task(t);

 * a really long time (120 seconds). If that happens, print out

 * a warning.

 */

static void check_hung_uninterruptible_tasks(void)

static void check_hung_uninterruptible_tasks(unsigned long timeout)

{

	int max_count = sysctl_hung_task_check_count;

	unsigned long now = get_timestamp();

			goto unlock;

		/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */

		if (t->state == TASK_UNINTERRUPTIBLE)

			check_hung_task(t, now);

			check_hung_task(t, now, timeout);

	} while_each_thread(g, t);

 unlock:

	read_unlock(&tasklist_lock);

	update_poll_jiffies();

	for ( ; ; ) {

		unsigned long timeout;

		while (schedule_timeout_interruptible(hung_task_poll_jiffies));

		check_hung_uninterruptible_tasks();

		/*

		 * Need to cache timeout here to avoid timeout being set

		 * to 0 via sysctl while inside check_hung_*_tasks().

		 */

		timeout = sysctl_hung_task_timeout_secs;

		if (timeout)

			check_hung_uninterruptible_tasks(timeout);

	}

	return 0;