On 04/05/2017 at 04:08 PM, Mike Galbraith wrote:
> locking/rtmutex: Fix preempt leak in __rt_mutex_futex_unlock()
>
> mark_wakeup_next_waiter() already disables preemption, doing so
> again leaves us with an unpaired preempt_disable().
You can also fix the corresponding comment in rt_mutex_postunlock():
/* Pairs with preempt_disable() in rt_mutex_slowunlock() */
preempt_enable();
Thanks,
Xunlei
>
> Signed-off-by: Mike Galbraith <efault@xxxxxx>
> ---
> kernel/locking/rtmutex.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -1581,13 +1581,13 @@ bool __sched __rt_mutex_futex_unlock(str
> return false; /* done */
> }
>
> - mark_wakeup_next_waiter(wake_q, lock);
> /*
> - * We've already deboosted, retain preempt_disabled when dropping
> - * the wait_lock to avoid inversion until the wakeup. Matched
> - * by rt_mutex_postunlock();
> + * We've already deboosted, mark_wakeup_next_waiter() will
> + * retain preempt_disabled when we drop the wait_lock, to
> + * avoid inversion prior to the wakeup. preempt_disable()
> + * therein pairs with rt_mutex_postunlock().
> */
> - preempt_disable();
> + mark_wakeup_next_waiter(wake_q, lock);
>
> return true; /* call postunlock() */
> }
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