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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: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210216103506.416286-3-vincent.donnefort@arm.com
This commit is contained in:
Vincent Donnefort 2021-02-16 10:35:05 +00:00 committed by Ingo Molnar
parent 3ae70c251f
commit 62f2506940
1 changed files with 16 additions and 3 deletions
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19
kernel/cpu.c
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@ -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) {
cpuhp_reset_state(st, prev_state);
__cpuhp_kick_ap(st);
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.
*/