Commit 3a51449b authored by Petr Mladek's avatar Petr Mladek Committed by Thomas Gleixner
Browse files

watchdog/softlockup: Remove obsolete check of last reported task 



commit 9cf57731 ("watchdog/softlockup: Replace "watchdog/%u" threads
 with cpu_stop_work") ensures that the watchdog is reliably touched during
a task switch.

As a result the check for an unnoticed task switch is not longer needed.

Remove the relevant code, which effectively reverts commit b1a8de1f
("softlockup: make detector be aware of task switch of processes hogging
cpu")

Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Ziljstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20191024114928.15377-2-pmladek@suse.com
parent d129479f

kernel/watchdog.c

+1 −17
Original line number Diff line number Diff line
@@ -173,7 +173,6 @@ static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); 
static DEFINE_PER_CPU(bool, softlockup_touch_sync);

static DEFINE_PER_CPU(bool, soft_watchdog_warn);

static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);

static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);

static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);

static unsigned long soft_lockup_nmi_warn;
@@ -413,22 +412,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) 
			return HRTIMER_RESTART;



		/* only warn once */

		if (__this_cpu_read(soft_watchdog_warn) == true) {

			/*

			 * When multiple processes are causing softlockups the

			 * softlockup detector only warns on the first one

			 * because the code relies on a full quiet cycle to

			 * re-arm.  The second process prevents the quiet cycle

			 * and never gets reported.  Use task pointers to detect

			 * this.

			 */

			if (__this_cpu_read(softlockup_task_ptr_saved) !=

			    current) {

				__this_cpu_write(soft_watchdog_warn, false);

				__touch_watchdog();

			}

		if (__this_cpu_read(soft_watchdog_warn) == true)

			return HRTIMER_RESTART;

		}



		if (softlockup_all_cpu_backtrace) {

			/* Prevent multiple soft-lockup reports if one cpu is already
@@ -444,7 +429,6 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) 
		pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",

			smp_processor_id(), duration,

			current->comm, task_pid_nr(current));

		__this_cpu_write(softlockup_task_ptr_saved, current);

		print_modules();

		print_irqtrace_events(current);

		if (regs)

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