Re: [PATCH v8 2/2] drm/i915/guc: Close deregister-context race against CT-loss

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Wed, Dec 20, 2023 at 11:08:59PM +0000, Teres Alexis, Alan Previn wrote:
> On Wed, 2023-12-13 at 16:23 -0500, Vivi, Rodrigo wrote:
> > On Tue, Dec 12, 2023 at 08:57:16AM -0800, Alan Previn wrote:
> > > If we are at the end of suspend or very early in resume
> > > its possible an async fence signal (via rcu_call) is triggered
> > > to free_engines which could lead us to the execution of
> > > the context destruction worker (after a prior worker flush).
> alan:snip
> > 
> > > Thus, do an unroll in guc_lrc_desc_unpin and deregister_destroyed_-
> > > contexts if guc_lrc_desc_unpin fails due to CT send falure.
> > > When unrolling, keep the context in the GuC's destroy-list so
> > > it can get picked up on the next destroy worker invocation
> > > (if suspend aborted) or get fully purged as part of a GuC
> > > sanitization (end of suspend) or a reset flow.
> > > 
> > > Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com>
> > > Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
> > > Tested-by: Mousumi Jana <mousumi.jana@intel.com>
> > > Acked-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> > 
> > Thanks for all the explanations, patience and great work!
> > 
> > Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> 
> alan: Thanks Rodrigo for the RB last week, just quick update:
> 
> I've cant reproduce the BAT failures that seem to be intermittent
> on platform and test - however, a noticable number of failures
> do keep occuring on i915_selftest @live @requests where the
> last test leaked a wakeref and the failing test hangs waiting
> for gt to idle before starting its test.
> 
> i have to debug this further although from code inspection
> is unrelated to the patches in this series.
> Hopefully its a different issue.

Yeap, likely not related. Anyway, I'm sorry for not merging
this sooner. Could you please send a rebased version? This
on is not applying cleanly anymore.