Re: [PATCH v2] drm/i915: Order two completing nop_submit_request

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 06/10/2017 12:56, Chris Wilson wrote:
> If two nop's (requests in-flight following a wedged device) complete at
> the same time, the global_seqno value written to the HWSP is undefined
> as the two threads are not serialized.
> 
> v2: Use irqsafe spinlock. We expect the callback may be called from
> inside another irq spinlock, so we can't unconditionally restore irqs.
> 
> Fixes: ce1135c7de64 ("drm/i915: Complete requests in nop_submit_request")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> #v1
> ---
>   drivers/gpu/drm/i915/i915_gem.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index ab8c6946fea4..6a6974ed8f74 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3014,10 +3014,15 @@ void i915_gem_reset_finish(struct drm_i915_private *dev_priv)
>   
>   static void nop_submit_request(struct drm_i915_gem_request *request)
>   {
> +	unsigned long flags;
> +
>   	GEM_BUG_ON(!i915_terminally_wedged(&request->i915->gpu_error));
>   	dma_fence_set_error(&request->fence, -EIO);
> -	i915_gem_request_submit(request);
> +
> +	spin_lock_irqsave(&request->engine->timeline->lock, flags);
> +	__i915_gem_request_submit(request);
>   	intel_engine_init_global_seqno(request->engine, request->global_seqno);
> +	spin_unlock_irqrestore(&request->engine->timeline->lock, flags);
>   }
>   
>   static void engine_set_wedged(struct intel_engine_cs *engine)
> 

Ooops..

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko

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