Re: [PATCH 1/2] drm/i915: Stop touching hangcheck.seqno from intel_engine_init_global_seqno()

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> The hangcheck runs independently to the main flow of seqno through the
> driver. However, we have an odd coupling of the seqno reset that is
> unwelcome, and if poked at just the right rate can cause spurious hangs
> (e.g. gem_exec_whisper) on an apparently idle engine.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>

Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

> ---
>  drivers/gpu/drm/i915/intel_engine_cs.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index 7681d17ce454..f3cb7e931317 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -265,6 +265,7 @@ void intel_engine_init_global_seqno(struct intel_engine_cs *engine, u32 seqno)
>  	struct drm_i915_private *dev_priv = engine->i915;
>  
>  	GEM_BUG_ON(!intel_engine_is_idle(engine));
> +	GEM_BUG_ON(i915_gem_active_isset(&engine->timeline->last_request));
>  
>  	/* Our semaphore implementation is strictly monotonic (i.e. we proceed
>  	 * so long as the semaphore value in the register/page is greater
> @@ -284,9 +285,6 @@ void intel_engine_init_global_seqno(struct intel_engine_cs *engine, u32 seqno)
>  	intel_write_status_page(engine, I915_GEM_HWS_INDEX, seqno);
>  	clear_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted);
>  
> -	GEM_BUG_ON(i915_gem_active_isset(&engine->timeline->last_request));
> -	engine->hangcheck.seqno = seqno;
> -
>  	/* After manually advancing the seqno, fake the interrupt in case
>  	 * there are any waiters for that seqno.
>  	 */
> -- 
> 2.11.0
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