Re: [PATCH 4/4] drm/i915: Wait for reset to complete before returning from debugfs/i915_wedged

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

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

> Provide some serialisation between user operations by waiting for the
> reset initiated by setting i915_wedged to complete.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 5fdf8c137235..ada823815b8a 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -4129,6 +4129,10 @@ i915_wedged_set(void *data, u64 val)
>  	i915_handle_error(dev_priv, val,
>  			  "Manually setting wedged to %llu", val);
>  
> +	wait_on_bit(&dev_priv->gpu_error.flags,
> +		    I915_RESET_HANDOFF,
> +		    TASK_UNINTERRUPTIBLE);
> +

But what happens here if we have already prevented the reset and
the handoff never clears? Seems like it is a stuck task as the
handoff is not cleared on error path in i915_reset.

-Mika


>  	return 0;
>  }
>  
> -- 
> 2.11.0
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