Messages in this thread | | | Date | Wed, 23 Jul 2014 09:51:57 +0200 | From | Maarten Lankhorst <> | Subject | Re: [Nouveau] [PATCH 09/17] drm/radeon: use common fence implementation for fences |
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op 23-07-14 09:37, Christian König schreef: > Am 23.07.2014 09:31, schrieb Daniel Vetter: >> On Wed, Jul 23, 2014 at 9:26 AM, Christian König >> <deathsimple@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
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