Re: [PATCH 2/3] drm/i915: Call synchronize_irq() after resetting the GPU

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

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

> When we reset the GPU, we want to reinitialise it from a known step. In
> order to do so, we have to flush any pending operations from the irq
> handler and its tasklets. Add a missing synchronize_irq().
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 1418c1c522cb..d037da8ea449 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2581,8 +2581,6 @@ static void i915_gem_reset_engine(struct intel_engine_cs *engine)
>  	struct i915_gem_context *incomplete_ctx;
>  	bool ring_hung;
>  
> -	/* Ensure irq handler finishes, and not run again. */
> -	tasklet_kill(&engine->irq_tasklet);
>  	if (engine->irq_seqno_barrier)
>  		engine->irq_seqno_barrier(engine);
>  
> @@ -2624,6 +2622,11 @@ void i915_gem_reset(struct drm_i915_private *dev_priv)
>  
>  	i915_gem_retire_requests(dev_priv);
>  
> +	/* Ensure irq handler finishes, and not run again. */
> +	synchronize_irq(dev_priv->drm.irq);
> +	for_each_engine(engine, dev_priv)
> +		tasklet_kill(&engine->irq_tasklet);
> +

But you still might get one tasklet run if there was interrupt pending,
post reset?

How about this kind of ordering:

engine->disable_irq();
synchronize_irq();
tasklet_kill(engine);

intel_gpu_reset();
i915_gem_reset();

Perhaps I am paranoid but I want to guarantee the frozen state
before we hit the reset button.

-Mika


>  	for_each_engine(engine, dev_priv)
>  		i915_gem_reset_engine(engine);
>  
> -- 
> 2.9.3
>
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