From: Vincent Donnefort <[email protected]> The atomic states (between CPUHP_AP_IDLE_DEAD and CPUHP_AP_ONLINE) are triggered by the CPUHP_BRINGUP_CPU step. If the latter doesn't run, none of the atomic can. Hence, rollback is not possible after a hotunplug CPUHP_BRINGUP_CPU step failure and the "fail" interface shouldn't allow it. Moreover, the current CPUHP_BRINGUP_CPU teardown callback (finish_cpu()) cannot fail anyway.
Signed-off-by: Vincent Donnefort <[email protected]> --- kernel/cpu.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 9121edf..bcd7b2a 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2216,9 +2216,14 @@ static ssize_t write_cpuhp_fail(struct device *dev, return -EINVAL; /* - * Cannot fail STARTING/DYING callbacks. + * Cannot fail STARTING/DYING callbacks. Also, those callbacks are + * triggered by BRINGUP_CPU bringup callback. Therefore, the latter + * can't fail during hotunplug, as it would mean we have no way of + * rolling back the atomic states that have been previously teared + * down. */ - if (cpuhp_is_atomic_state(fail)) + if (cpuhp_is_atomic_state(fail) || + (fail == CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)) return -EINVAL; /* -- 2.7.4
