Re: [Freedreno] [PATCH 06/14] drm/msm: Protect ring->submits with it's own lock

[Jordan Crouse]

On Sun, Oct 04, 2020 at 12:21:38PM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@xxxxxxxxxxxx>
> 
> One less place to rely on dev->struct_mutex.
> 

Reviewed-by: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>

> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/msm_gem_submit.c |  2 ++
>  drivers/gpu/drm/msm/msm_gpu.c        | 37 ++++++++++++++++++++++------
>  drivers/gpu/drm/msm/msm_ringbuffer.c |  1 +
>  drivers/gpu/drm/msm/msm_ringbuffer.h |  6 +++++
>  4 files changed, 39 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> index aa5c60a7132d..e1d1f005b3d4 100644
> --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> @@ -63,7 +63,9 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev,
>  void msm_gem_submit_free(struct msm_gem_submit *submit)
>  {
>  	dma_fence_put(submit->fence);
> +	spin_lock(&submit->ring->submit_lock);
>  	list_del(&submit->node);
> +	spin_unlock(&submit->ring->submit_lock);
>  	put_pid(submit->pid);
>  	msm_submitqueue_put(submit->queue);
>  
> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> index ca8c95b32c8b..8d1e254f964a 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.c
> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> @@ -270,6 +270,7 @@ static void update_fences(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
>  {
>  	struct msm_gem_submit *submit;
>  
> +	spin_lock(&ring->submit_lock);
>  	list_for_each_entry(submit, &ring->submits, node) {
>  		if (submit->seqno > fence)
>  			break;
> @@ -277,6 +278,7 @@ static void update_fences(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
>  		msm_update_fence(submit->ring->fctx,
>  			submit->fence->seqno);
>  	}
> +	spin_unlock(&ring->submit_lock);
>  }
>  
>  #ifdef CONFIG_DEV_COREDUMP
> @@ -430,11 +432,14 @@ find_submit(struct msm_ringbuffer *ring, uint32_t fence)
>  {
>  	struct msm_gem_submit *submit;
>  
> -	WARN_ON(!mutex_is_locked(&ring->gpu->dev->struct_mutex));
> -
> -	list_for_each_entry(submit, &ring->submits, node)
> -		if (submit->seqno == fence)
> +	spin_lock(&ring->submit_lock);
> +	list_for_each_entry(submit, &ring->submits, node) {
> +		if (submit->seqno == fence) {
> +			spin_unlock(&ring->submit_lock);
>  			return submit;
> +		}
> +	}
> +	spin_unlock(&ring->submit_lock);
>  
>  	return NULL;
>  }
> @@ -523,8 +528,10 @@ static void recover_worker(struct work_struct *work)
>  		for (i = 0; i < gpu->nr_rings; i++) {
>  			struct msm_ringbuffer *ring = gpu->rb[i];
>  
> +			spin_lock(&ring->submit_lock);
>  			list_for_each_entry(submit, &ring->submits, node)
>  				gpu->funcs->submit(gpu, submit);
> +			spin_unlock(&ring->submit_lock);
>  		}
>  	}
>  
> @@ -711,7 +718,6 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
>  static void retire_submits(struct msm_gpu *gpu)
>  {
>  	struct drm_device *dev = gpu->dev;
> -	struct msm_gem_submit *submit, *tmp;
>  	int i;
>  
>  	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
> @@ -720,9 +726,24 @@ static void retire_submits(struct msm_gpu *gpu)
>  	for (i = 0; i < gpu->nr_rings; i++) {
>  		struct msm_ringbuffer *ring = gpu->rb[i];
>  
> -		list_for_each_entry_safe(submit, tmp, &ring->submits, node) {
> -			if (dma_fence_is_signaled(submit->fence))
> +		while (true) {
> +			struct msm_gem_submit *submit = NULL;
> +
> +			spin_lock(&ring->submit_lock);
> +			submit = list_first_entry_or_null(&ring->submits,
> +					struct msm_gem_submit, node);
> +			spin_unlock(&ring->submit_lock);
> +
> +			/*
> +			 * If no submit, we are done.  If submit->fence hasn't
> +			 * been signalled, then later submits are not signalled
> +			 * either, so we are also done.
> +			 */
> +			if (submit && dma_fence_is_signaled(submit->fence)) {
>  				retire_submit(gpu, ring, submit);
> +			} else {
> +				break;
> +			}
>  		}
>  	}
>  }
> @@ -765,7 +786,9 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>  
>  	submit->seqno = ++ring->seqno;
>  
> +	spin_lock(&ring->submit_lock);
>  	list_add_tail(&submit->node, &ring->submits);
> +	spin_unlock(&ring->submit_lock);
>  
>  	msm_rd_dump_submit(priv->rd, submit, NULL);
>  
> diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
> index 1b6958e908dc..4d2a2a4abef8 100644
> --- a/drivers/gpu/drm/msm/msm_ringbuffer.c
> +++ b/drivers/gpu/drm/msm/msm_ringbuffer.c
> @@ -46,6 +46,7 @@ struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id,
>  	ring->memptrs_iova = memptrs_iova;
>  
>  	INIT_LIST_HEAD(&ring->submits);
> +	spin_lock_init(&ring->submit_lock);
>  	spin_lock_init(&ring->preempt_lock);
>  
>  	snprintf(name, sizeof(name), "gpu-ring-%d", ring->id);
> diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.h b/drivers/gpu/drm/msm/msm_ringbuffer.h
> index 4956d1bc5d0e..fe55d4a1aa16 100644
> --- a/drivers/gpu/drm/msm/msm_ringbuffer.h
> +++ b/drivers/gpu/drm/msm/msm_ringbuffer.h
> @@ -39,7 +39,13 @@ struct msm_ringbuffer {
>  	int id;
>  	struct drm_gem_object *bo;
>  	uint32_t *start, *end, *cur, *next;
> +
> +	/*
> +	 * List of in-flight submits on this ring.  Protected by submit_lock.
> +	 */
>  	struct list_head submits;
> +	spinlock_t submit_lock;
> +
>  	uint64_t iova;
>  	uint32_t seqno;
>  	uint32_t hangcheck_fence;
> -- 
> 2.26.2
> 
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