On Mon, Jan 11, 2021 at 05:10:45PM +0000, vincent.donnef...@arm.com wrote: > From: Vincent Donnefort <vincent.donnef...@arm.com> > > 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 <vincent.donnef...@arm.com> > --- > 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;
Should we instead disallow failing any state that has .cant_stop ?
