[PATCH] drm/amdgpu:fix race condition

[Christian König]

Am 10.04.2017 um 12:24 schrieb Monk Liu:
> sequence is protected by spinlock so don't access sequence
> in paramter seq when invoking this function.
>
> ~0 means to get the latest sequence number and 0 means none to
> get.
>
> Change-Id: Ib7a03f3cf5594deeb4ad333cc59b47a6bddfd1ad
> Signed-off-by: Monk Liu <Monk.Liu at amd.com>

Reviewed-by: Christian König <christian.koenig at amd.com>

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 3 +++
>   include/uapi/drm/amdgpu_drm.h           | 5 ++++-
>   2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> index 6d86eae..b4bbbb3 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> @@ -277,6 +277,9 @@ struct fence *amdgpu_ctx_get_fence(struct amdgpu_ctx *ctx,
>   
>   	spin_lock(&ctx->ring_lock);
>   
> +	if (seq == ~0ull)
> +		seq = ctx->rings[ring->idx].sequence - 1;
> +
>   	if (seq >= cring->sequence) {
>   		spin_unlock(&ctx->ring_lock);
>   		return ERR_PTR(-EINVAL);
> diff --git a/include/uapi/drm/amdgpu_drm.h b/include/uapi/drm/amdgpu_drm.h
> index 34e5f93..3243409 100644
> --- a/include/uapi/drm/amdgpu_drm.h
> +++ b/include/uapi/drm/amdgpu_drm.h
> @@ -297,7 +297,10 @@ union drm_amdgpu_gem_wait_idle {
>   };
>   
>   struct drm_amdgpu_wait_cs_in {
> -	/** Command submission handle */
> +	/* Command submission handle
> +         * handle equals 0 means none to wait for
> +         * handle equal ~0ull meanas wait for the latest sequence number
> +         */
>   	__u64 handle;
>   	/** Absolute timeout to wait */
>   	__u64 timeout;