On Mon, Apr 07, 2014 at 10:42:56AM +0100, Chris Wilson wrote: > On Sun, Apr 06, 2014 at 11:35:03AM -0700, Ben Widawsky wrote: > > On Sat, Apr 05, 2014 at 07:45:28PM -0700, Ben Widawsky wrote: > > > The issue I was seeing appeared to seeing from sigkill. In such a case, > > > the process may want to die before the context/work/address space is > > > freeable. For example: > > > 1. evict_vm called for whatever reason > > > 2. wait_seqno because the VMA is still active > > > > hmm something isn't right here. Why did I get to wait_seqno if pin_count > > was 0? Just FYI, this wasn't hypothetical. I did trace it all the way to > > exactly ERESTARTSYS from wait_seqno. > > > > By the way, another option in evict would be: > > while(ret = (i915_vma_unbind(vma) == -ERESTARTSYS)); > > WARN_ON(ret); > > > > > 3. receive signal break out of wait_seqno > > > 4. return to evict_vm and the above WARN > > > > > > Our error handling from there just spirals. > > > > > > One issue I have with our current code is I'd really like eviction to > > > not be able to fail (obviously extreme cases are unavoidable). > > This is unrealistic since we must support X which uses sigtimer. > > > > Perhaps > > > one other solution would be to make sure the context is idled before > > > evicting its VM. > > Indeed. > > Anyway, I do concur that wrapping i915_driver_preclose() with > > dev_priv->mm.interruptible = false; > > would make us both happy. Isn't the backtrace just fallout from the lifetime rules being a bit funny? We didn't uninterruptibly stall for any still active bo when the drm fd gets closed, why do we suddenly need to do that with ppgtts? Iirc requests hold a ref on the context, contexts hold a ref on the ppgtt and so the entire thing should only dissipate once it's really idle. Imo just doing uninterruptible sleeps tastes way too much like duct-tape. I can be convinced of duct-tape if the tradeoffs really strongly suggests it's the right thing (e.g. the shrinker lock stealing, even though we've paid a hefty price in accidental complexity with that one), but that needs some good justification. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
