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Message-ID: <20201005135602.GR438822@phenom.ffwll.local>
Date: Mon, 5 Oct 2020 15:56:02 +0200
From: Daniel Vetter <daniel@...ll.ch>
To: Rob Clark <robdclark@...il.com>
Cc: dri-devel@...ts.freedesktop.org,
Rob Clark <robdclark@...omium.org>,
Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
"open list:DRM DRIVER FOR MSM ADRENO GPU"
<linux-arm-msm@...r.kernel.org>,
"open list:DRM DRIVER FOR MSM ADRENO GPU"
<freedreno@...ts.freedesktop.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/14] drm/msm: Refcount submits
On Sun, Oct 04, 2020 at 12:21:39PM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
>
> Before we remove dev->struct_mutex from the retire path, we have to deal
> with the situation of a submit retiring before the submit ioctl returns.
>
> To deal with this, ring->submits will hold a reference to the submit,
> which is dropped when the submit is retired. And the submit ioctl path
> holds it's own ref, which it drops when it is done with the submit.
>
> Also, add to submit list *after* getting/pinning bo's, to prevent badness
> in case the completed fence is corrupted, and retire_worker mistakenly
> believes the submit is done too early.
>
> Signed-off-by: Rob Clark <robdclark@...omium.org>
Why not embed the dma_fence instead of pointer and use that refcount? i915
does that, and imo kinda makes sense instead of more refcounted things.
But might not make sense for msm.
-Daniel
> ---
> drivers/gpu/drm/msm/msm_drv.h | 1 -
> drivers/gpu/drm/msm/msm_gem.h | 13 +++++++++++++
> drivers/gpu/drm/msm/msm_gem_submit.c | 12 ++++++------
> drivers/gpu/drm/msm/msm_gpu.c | 21 ++++++++++++++++-----
> 4 files changed, 35 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index 50978e5db376..535f9e718e2d 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -277,7 +277,6 @@ void msm_unregister_mmu(struct drm_device *dev, struct msm_mmu *mmu);
>
> bool msm_use_mmu(struct drm_device *dev);
>
> -void msm_gem_submit_free(struct msm_gem_submit *submit);
> int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
> struct drm_file *file);
>
> diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
> index a1bf741b9b89..e05b1530aca6 100644
> --- a/drivers/gpu/drm/msm/msm_gem.h
> +++ b/drivers/gpu/drm/msm/msm_gem.h
> @@ -136,6 +136,7 @@ void msm_gem_free_work(struct work_struct *work);
> * lasts for the duration of the submit-ioctl.
> */
> struct msm_gem_submit {
> + struct kref ref;
> struct drm_device *dev;
> struct msm_gpu *gpu;
> struct msm_gem_address_space *aspace;
> @@ -169,6 +170,18 @@ struct msm_gem_submit {
> } bos[];
> };
>
> +void __msm_gem_submit_destroy(struct kref *kref);
> +
> +static inline void msm_gem_submit_get(struct msm_gem_submit *submit)
> +{
> + kref_get(&submit->ref);
> +}
> +
> +static inline void msm_gem_submit_put(struct msm_gem_submit *submit)
> +{
> + kref_put(&submit->ref, __msm_gem_submit_destroy);
> +}
> +
> /* helper to determine of a buffer in submit should be dumped, used for both
> * devcoredump and debugfs cmdstream dumping:
> */
> diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> index e1d1f005b3d4..7d653bdc92dc 100644
> --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> @@ -42,6 +42,7 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev,
> if (!submit)
> return NULL;
>
> + kref_init(&submit->ref);
> submit->dev = dev;
> submit->aspace = queue->ctx->aspace;
> submit->gpu = gpu;
> @@ -60,12 +61,12 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev,
> return submit;
> }
>
> -void msm_gem_submit_free(struct msm_gem_submit *submit)
> +void __msm_gem_submit_destroy(struct kref *kref)
> {
> + struct msm_gem_submit *submit =
> + container_of(kref, struct msm_gem_submit, ref);
> +
> 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);
>
> @@ -805,8 +806,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
> submit_cleanup(submit);
> if (has_ww_ticket)
> ww_acquire_fini(&submit->ticket);
> - if (ret)
> - msm_gem_submit_free(submit);
> + msm_gem_submit_put(submit);
> out_unlock:
> if (ret && (out_fence_fd >= 0))
> put_unused_fd(out_fence_fd);
> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> index 8d1e254f964a..fd3fc6f36ab1 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.c
> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> @@ -712,7 +712,12 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
>
> pm_runtime_mark_last_busy(&gpu->pdev->dev);
> pm_runtime_put_autosuspend(&gpu->pdev->dev);
> - msm_gem_submit_free(submit);
> +
> + spin_lock(&ring->submit_lock);
> + list_del(&submit->node);
> + spin_unlock(&ring->submit_lock);
> +
> + msm_gem_submit_put(submit);
> }
>
> static void retire_submits(struct msm_gpu *gpu)
> @@ -786,10 +791,6 @@ 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);
>
> update_sw_cntrs(gpu);
> @@ -816,6 +817,16 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
> msm_gem_active_get(drm_obj, gpu);
> }
>
> + /*
> + * ring->submits holds a ref to the submit, to deal with the case
> + * that a submit completes before msm_ioctl_gem_submit() returns.
> + */
> + msm_gem_submit_get(submit);
> +
> + spin_lock(&ring->submit_lock);
> + list_add_tail(&submit->node, &ring->submits);
> + spin_unlock(&ring->submit_lock);
> +
> gpu->funcs->submit(gpu, submit);
> priv->lastctx = submit->queue->ctx;
>
> --
> 2.26.2
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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