Commit 28168eca authored by Douglas Anderson's avatar Douglas Anderson Committed by Andrew Morton
Browse files

watchdog/hardlockup: move SMP barriers from common code to buddy code 

It's been suggested that since the SMP barriers are only potentially
useful for the buddy hardlockup detector, not the perf hardlockup
detector, that the barriers belong in the buddy code.  Let's move them and
add clearer comments about why they're needed.

Link: https://lkml.kernel.org/r/20230526184139.9.I5ab0a0eeb0bd52fb23f901d298c72fa5c396e22b@changeid


Signed-off-by: default avatarDouglas Anderson <dianders@chromium.org>
Suggested-by: default avatarPetr Mladek <pmladek@suse.com>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 7ece48b7

kernel/watchdog.c

+0 −6
Original line number Diff line number Diff line
@@ -109,9 +109,6 @@ EXPORT_SYMBOL(arch_touch_nmi_watchdog); 
void watchdog_hardlockup_touch_cpu(unsigned int cpu)

{

	per_cpu(watchdog_hardlockup_touched, cpu) = true;



	/* Match with smp_rmb() in watchdog_hardlockup_check() */

	smp_wmb();

}



static bool is_hardlockup(unsigned int cpu)
@@ -141,9 +138,6 @@ static void watchdog_hardlockup_kick(void) 


void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)

{

	/* Match with smp_wmb() in watchdog_hardlockup_touch_cpu() */

	smp_rmb();



	if (per_cpu(watchdog_hardlockup_touched, cpu)) {

		per_cpu(watchdog_hardlockup_touched, cpu) = false;

		return;

kernel/watchdog_buddy.c

+21 −0
Original line number Diff line number Diff line
@@ -51,6 +51,13 @@ void watchdog_hardlockup_enable(unsigned int cpu) 
	if (next_cpu < nr_cpu_ids)

		watchdog_hardlockup_touch_cpu(next_cpu);



	/*

	 * Makes sure that watchdog is touched on this CPU before

	 * other CPUs could see it in watchdog_cpus. The counter

	 * part is in watchdog_buddy_check_hardlockup().

	 */

	smp_wmb();



	cpumask_set_cpu(cpu, &watchdog_cpus);

}
@@ -68,6 +75,13 @@ void watchdog_hardlockup_disable(unsigned int cpu) 
	if (next_cpu < nr_cpu_ids)

		watchdog_hardlockup_touch_cpu(next_cpu);



	/*

	 * Makes sure that watchdog is touched on the next CPU before

	 * this CPU disappear in watchdog_cpus. The counter part is in

	 * watchdog_buddy_check_hardlockup().

	 */

	smp_wmb();



	cpumask_clear_cpu(cpu, &watchdog_cpus);

}
@@ -88,5 +102,12 @@ void watchdog_buddy_check_hardlockup(int hrtimer_interrupts) 
	if (next_cpu >= nr_cpu_ids)

		return;



	/*

	 * Make sure that the watchdog was touched on next CPU when

	 * watchdog_next_cpu() returned another one because of

	 * a change in watchdog_hardlockup_enable()/disable().

	 */

	smp_rmb();



	watchdog_hardlockup_check(next_cpu, NULL);

}