Hi Juergen, On 09/11/2020 16:38, Juergen Gross wrote:
Currently the lock for a single event channel needs to be taken with interrupts off, which causes deadlocks in some cases.Rework the per event channel lock to be non-blocking for the case of sending an event and removing the need for disabling interrupts for taking the lock. The lock is needed for avoiding races between event channel state changes (creation, closing, binding) against normal operations (set pending, [un]masking, priority changes). Use a rwlock, but with some restrictions: - Changing the state of an event channel (creation, closing, binding) needs to use write_lock(), with ASSERT()ing that the lock is taken as writer only when the state of the event channel is either before or after the locked region appropriate (either free or unbound). - Sending an event needs to use read_trylock() mostly, in case of not obtaining the lock the operation is omitted. This is needed as sending an event can happen with interrupts off (at least in some cases). - Dumping the event channel state for debug purposes is using read_trylock(), too, in order to avoid blocking in case the lock is taken as writer for a long time. - All other cases can use read_lock(). Fixes: e045199c7c9c54 ("evtchn: address races with evtchn_reset()") Signed-off-by: Juergen Gross <jgr...@suse.com>
Acked-by: Julien Grall <jgr...@amazon.com> Cheers, -- Julien Grall
