Commit 62f25069 authored by Vincent Donnefort's avatar Vincent Donnefort Committed by Ingo Molnar
Browse files

cpu/hotplug: CPUHP_BRINGUP_CPU failure exception 



The atomic states (between CPUHP_AP_IDLE_DEAD and CPUHP_AP_ONLINE) are
triggered by the CPUHP_BRINGUP_CPU step. If the latter fails, no atomic
state can be rolled back.

DEAD callbacks too can't fail and disallow recovery. As a consequence,
during hotunplug, the fail injection interface should prohibit all states
from CPUHP_BRINGUP_CPU to CPUHP_ONLINE.

Signed-off-by: default avatarVincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210216103506.416286-3-vincent.donnefort@arm.com
parent 3ae70c25

kernel/cpu.c

+16 −3
Original line number Diff line number Diff line
@@ -1045,9 +1045,13 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen, 
	 * to do the further cleanups.

	 */

	ret = cpuhp_down_callbacks(cpu, st, target);

	if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {

	if (ret && st->state < prev_state) {

		if (st->state == CPUHP_TEARDOWN_CPU) {

			cpuhp_reset_state(st, prev_state);

			__cpuhp_kick_ap(st);

		} else {

			WARN(1, "DEAD callback error for CPU%d", cpu);

		}

	}



out:
@@ -2221,6 +2225,15 @@ static ssize_t write_cpuhp_fail(struct device *dev, 
	if (cpuhp_is_atomic_state(fail))

		return -EINVAL;



	/*

	 * DEAD callbacks cannot fail...

	 * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter

	 * triggering STARTING callbacks, a failure in this state would

	 * hinder rollback.

	 */

	if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)

		return -EINVAL;



	/*

	 * Cannot fail anything that doesn't have callbacks.

	 */