linux-kernel - Re: [PATCH] drm/v3d: Add missing unlock

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Message-ID: <20220126205726.phfikh7kn3lks5ib@mail.igalia.com>
Date:   Wed, 26 Jan 2022 19:57:26 -0100
From:   Melissa Wen <mwen@...lia.com>
To:     Yongzhi Liu <lyz_cs@....edu.cn>
Cc:     emma@...olt.net, airlied@...ux.ie, daniel@...ll.ch,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/v3d: Add missing unlock

On 01/22, Yongzhi Liu wrote:
> [why]
> Unlock is needed on the error handling path to prevent dead lock.
> 
> [how]
> Fix this by adding drm_gem_unlock_reservations on the error handling path.
> 
> Signed-off-by: Yongzhi Liu <lyz_cs@....edu.cn>
> ---
>  drivers/gpu/drm/v3d/v3d_gem.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/v3d/v3d_gem.c b/drivers/gpu/drm/v3d/v3d_gem.c
> index c7ed2e1..0c989dc 100644
> --- a/drivers/gpu/drm/v3d/v3d_gem.c
> +++ b/drivers/gpu/drm/v3d/v3d_gem.c
> @@ -798,6 +798,8 @@ v3d_submit_cl_ioctl(struct drm_device *dev, void *data,
>  
>  		if (!render->base.perfmon) {
>  			ret = -ENOENT;
> +			drm_gem_unlock_reservations(last_job->bo,
> +				    last_job->bo_count, &acquire_ctx);
>  			goto fail;
Hi,

Nice catch!

As unlock is handle in fail_unreserve, I would suggest you to keep the
failures handling around there. In that case, the goto will target a
place between `fail_unreserve:` and `fail:`, i.e. calls
drm_gem_unlock_reservations (and the following cleanings) but don't call
mutex_unlock.

Thanks,

Melissa

>  		}
>  	}
> @@ -1027,6 +1029,8 @@ v3d_submit_csd_ioctl(struct drm_device *dev, void *data,
>  						     args->perfmon_id);
>  		if (!job->base.perfmon) {
>  			ret = -ENOENT;
> +			drm_gem_unlock_reservations(clean_job->bo, clean_job->bo_count,
> +						    &acquire_ctx);
>  			goto fail;
>  		}
>  	}
> -- 
> 2.7.4
> 

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