op 23-07-14 09:37, Christian K?nig schreef: > Am 23.07.2014 09:31, schrieb Daniel Vetter: >> On Wed, Jul 23, 2014 at 9:26 AM, Christian K?nig >> <deathsimple at vodafone.de> wrote: >>> It's not a locking problem I'm talking about here. Radeons lockup handling >>> kicks in when anything calls into the driver from the outside, if you have a >>> fence wait function that's called from the outside but doesn't handle >>> lockups you essentially rely on somebody else calling another radeon >>> function for the lockup to be resolved. >> So you don't have a timer in radeon that periodically checks whether >> progress is still being made? That's the approach we're using in i915, >> together with some tricks to kick any stuck waiters so that we can >> reliably step in and grab locks for the reset. > > We tried this approach, but it didn't worked at all. > > I already considered trying it again because of the upcoming fence > implementation, but reconsidering that when a driver is forced to change it's > handling because of the fence implementation that's just another hint that > there is something wrong here. As far as I can tell it wouldn't need to be reworked for the fence implementation currently, only the moment you want to allow callers outside of radeon. :-) Doing a GPU lockup recovery in the wait function would be messy even right now, you would hit a deadlock in ttm_bo_delayed_delete -> ttm_bo_cleanup_refs_and_unlock.
Regardless of the fence implementation, why would it be a good idea to do a full lockup recovery when some other driver is calling your wait function? That doesn't seem to be a nice thing to do, so I think a timeout is the best error you could return here, other drivers have to deal with that anyway. ~Maarten
