Re: [Intel-gfx] [PATCH v2 1/5] drm/i915: Fix request locking during error capture & debugfs dump

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, Jan 17, 2023 at 01:36:26PM -0800, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
> 
> When GuC support was added to error capture, the locking around the
> request object was broken. Fix it up.
> 
> The context based search manages the spinlocking around the search
> internally. So it needs to grab the reference count internally as
> well. The execlist only request based search relies on external
> locking, so it needs an external reference count. So no change to that
> code itself but the context version does change.
> 
> The only other caller is the code for dumping engine state to debugfs.
> That code wasn't previously getting an explicit reference at all as it
> does everything while holding the execlist specific spinlock. So that
> needs updaing as well as that spinlock doesn't help when using GuC
> submission. Rather than trying to conditionally get/put depending on
> submission model, just change it to always do the get/put.
> 
> In addition, intel_guc_find_hung_context() was not acquiring the
> correct spinlock before searching the request list. So fix that up too.

> Fixes: dc0dad365c5e ("drm/i915/guc: Fix for error capture after full GPU reset
> with GuC")

Must be one line.

> Fixes: 573ba126aef3 ("drm/i915/guc: Capture error state on context reset")

> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: John Harrison <John.C.Harrison@Intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Cc: Andrzej Hajda <andrzej.hajda@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> Cc: Michael Cheng <michael.cheng@intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Cc: Tejas Upadhyay <tejaskumarx.surendrakumar.upadhyay@intel.com>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Aravind Iddamsetty <aravind.iddamsetty@intel.com>
> Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
> Cc: Bruce Chang <yu.bruce.chang@intel.com>
> Cc: intel-gfx@lists.freedesktop.org

Is it possible to utilize --to --cc parameters to git send-email instead of
noisy Cc list?

...

> +	if (hung_rq)
> +		i915_request_put(hung_rq);

In Linux kernel the idiom is that freeing resources APIs should be NULL-aware
(or ERR_PTR aware or both). Does i915 follows that? If so, the test should be
inside i915_request_put() rather than in any of the callers.

...

> @@ -4847,6 +4857,7 @@ void intel_guc_find_hung_context(struct intel_engine_cs *engine)
>  			xa_lock(&guc->context_lookup);
>  			goto done;
>  		}
> +
>  next:
>  		intel_context_put(ce);
>  		xa_lock(&guc->context_lookup);

Stray change.

-- 
With Best Regards,
Andy Shevchenko