[Intel-gfx] [PATCH] drm/i915: Be defensive and don't assume PSR has any commit to sync against

[Ville Syrjälä]

On Tue, Sep 04, 2018 at 05:29:02PM +0100, Chris Wilson wrote:
> If the previous modeset commit has completed and is no longer part of
> the crtc state, skip waiting for it.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107792
> Fixes: c44301fce614 ("drm/i915: Allow control of PSR at runtime through debugfs, v6")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_psr.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
> index 21984d4c08ed..bddc9c7c681e 100644
> --- a/drivers/gpu/drm/i915/intel_psr.c
> +++ b/drivers/gpu/drm/i915/intel_psr.c
> @@ -834,6 +834,7 @@ int intel_psr_set_debugfs_mode(struct drm_i915_private *dev_priv,
>  	struct drm_device *dev = &dev_priv->drm;
>  	struct drm_connector_state *conn_state;
>  	struct intel_crtc_state *crtc_state = NULL;
> +	struct drm_crtc_commit *commit = NULL;
>  	struct drm_crtc *crtc;
>  	struct intel_dp *dp;
>  	int ret;
> @@ -860,12 +861,15 @@ int intel_psr_set_debugfs_mode(struct drm_i915_private *dev_priv,
>  			return ret;
>  
>  		crtc_state = to_intel_crtc_state(crtc->state);
> -		ret = wait_for_completion_interruptible(&crtc_state->base.commit->hw_done);
> -	} else
> -		ret = wait_for_completion_interruptible(&conn_state->commit->hw_done);
> -
> -	if (ret)
> -		return ret;
> +		commit = crtc_state->base.commit;
> +	} else {
> +		commit = conn_state->commit;

I can't even find where we clear state->commit after its done.
Do we just leave it pointing at freed memory or something? Also I
can't figure out why drm_atomic_helper_commit_hw_done() copies
the commit also to the old state.

> +	}
> +	if (commit) {
> +		ret = wait_for_completion_interruptible(&commit->hw_done);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	ret = mutex_lock_interruptible(&dev_priv->psr.lock);
>  	if (ret)
> -- 
> 2.19.0.rc1
> 
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-- 
Ville Syrjälä
Intel