Messages in this thread | | | Date | Wed, 21 Aug 2019 15:44:37 +0200 | From | Sebastian Andrzej Siewior <> | Subject | Re: [RT PATCH 1/3] hrtimer: Use READ_ONCE to access timer->base in hrimer_grab_expiry_lock() |
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On 2019-08-21 10:24:07 [+0100], Julien Grall wrote: > The update to timer->base is protected by the base->cpu_base->lock(). > However, hrtimer_grab_expirty_lock() does not access it with the lock. > > So it would theorically be possible to have timer->base changed under > our feet. We need to prevent the compiler to refetch timer->base so the > check and the access is performed on the same base.
It is not a problem if the timer's bases changes. We get here because we want to help the timer to complete its callback. The base can only change if the timer gets re-armed on another CPU which means is completed callback. In every case we can cancel the timer on the next iteration.
Sebastian
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