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Date: Wed, 10 Nov 2021 08:55:04 -0800
From: Rob Clark <robdclark@...il.com>
To: Akhil P Oommen <akhilpo@...eaurora.org>
Cc: dri-devel <dri-devel@...ts.freedesktop.org>,
Rob Clark <robdclark@...omium.org>,
David Airlie <airlied@...ux.ie>,
freedreno <freedreno@...ts.freedesktop.org>,
open list <linux-kernel@...r.kernel.org>,
"moderated list:DMA BUFFER SHARING FRAMEWORK"
<linaro-mm-sig@...ts.linaro.org>,
"open list:DRM DRIVER FOR MSM ADRENO GPU"
<linux-arm-msm@...r.kernel.org>, Sean Paul <sean@...rly.run>,
Christian König <christian.koenig@....com>,
"open list:DMA BUFFER SHARING FRAMEWORK"
<linux-media@...r.kernel.org>
Subject: Re: [PATCH v4 07/13] drm/msm: Track "seqno" fences by idr
On Wed, Nov 10, 2021 at 7:28 AM Akhil P Oommen <akhilpo@...eaurora.org> wrote:
>
> On 7/28/2021 6:36 AM, Rob Clark wrote:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > Previously the (non-fd) fence returned from submit ioctl was a raw
> > seqno, which is scoped to the ring. But from UABI standpoint, the
> > ioctls related to seqno fences all specify a submitqueue. We can
> > take advantage of that to replace the seqno fences with a cyclic idr
> > handle.
> >
> > This is in preperation for moving to drm scheduler, at which point
> > the submit ioctl will return after queuing the submit job to the
> > scheduler, but before the submit is written into the ring (and
> > therefore before a ring seqno has been assigned). Which means we
> > need to replace the dma_fence that userspace may need to wait on
> > with a scheduler fence.
> >
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > Acked-by: Christian König <christian.koenig@....com>
> > ---
> > drivers/gpu/drm/msm/msm_drv.c | 30 +++++++++++++++++--
> > drivers/gpu/drm/msm/msm_fence.c | 42 ---------------------------
> > drivers/gpu/drm/msm/msm_fence.h | 3 --
> > drivers/gpu/drm/msm/msm_gem.h | 1 +
> > drivers/gpu/drm/msm/msm_gem_submit.c | 23 ++++++++++++++-
> > drivers/gpu/drm/msm/msm_gpu.h | 5 ++++
> > drivers/gpu/drm/msm/msm_submitqueue.c | 5 ++++
> > 7 files changed, 61 insertions(+), 48 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> > index 9b8fa2ad0d84..1594ae39d54f 100644
> > --- a/drivers/gpu/drm/msm/msm_drv.c
> > +++ b/drivers/gpu/drm/msm/msm_drv.c
> > @@ -911,6 +911,7 @@ static int msm_ioctl_wait_fence(struct drm_device *dev, void *data,
> > ktime_t timeout = to_ktime(args->timeout);
> > struct msm_gpu_submitqueue *queue;
> > struct msm_gpu *gpu = priv->gpu;
> > + struct dma_fence *fence;
> > int ret;
> >
> > if (args->pad) {
> > @@ -925,10 +926,35 @@ static int msm_ioctl_wait_fence(struct drm_device *dev, void *data,
> > if (!queue)
> > return -ENOENT;
> >
> > - ret = msm_wait_fence(gpu->rb[queue->prio]->fctx, args->fence, &timeout,
> > - true);
> > + /*
> > + * Map submitqueue scoped "seqno" (which is actually an idr key)
> > + * back to underlying dma-fence
> > + *
> > + * The fence is removed from the fence_idr when the submit is
> > + * retired, so if the fence is not found it means there is nothing
> > + * to wait for
> > + */
> > + ret = mutex_lock_interruptible(&queue->lock);
> > + if (ret)
> > + return ret;
> > + fence = idr_find(&queue->fence_idr, args->fence);
> > + if (fence)
> > + fence = dma_fence_get_rcu(fence);
> > + mutex_unlock(&queue->lock);
> > +
> > + if (!fence)
> > + return 0;
> >
> > + ret = dma_fence_wait_timeout(fence, true, timeout_to_jiffies(&timeout));
> > + if (ret == 0) {
> > + ret = -ETIMEDOUT;
> > + } else if (ret != -ERESTARTSYS) {
> > + ret = 0;
> > + }
> > +
> > + dma_fence_put(fence);
> > msm_submitqueue_put(queue);
> > +
> > return ret;
> > }
> >
> > diff --git a/drivers/gpu/drm/msm/msm_fence.c b/drivers/gpu/drm/msm/msm_fence.c
> > index b92a9091a1e2..f2cece542c3f 100644
> > --- a/drivers/gpu/drm/msm/msm_fence.c
> > +++ b/drivers/gpu/drm/msm/msm_fence.c
> > @@ -24,7 +24,6 @@ msm_fence_context_alloc(struct drm_device *dev, volatile uint32_t *fenceptr,
> > strncpy(fctx->name, name, sizeof(fctx->name));
> > fctx->context = dma_fence_context_alloc(1);
> > fctx->fenceptr = fenceptr;
> > - init_waitqueue_head(&fctx->event);
> > spin_lock_init(&fctx->spinlock);
> >
> > return fctx;
> > @@ -45,53 +44,12 @@ static inline bool fence_completed(struct msm_fence_context *fctx, uint32_t fenc
> > (int32_t)(*fctx->fenceptr - fence) >= 0;
> > }
> >
> > -/* legacy path for WAIT_FENCE ioctl: */
> > -int msm_wait_fence(struct msm_fence_context *fctx, uint32_t fence,
> > - ktime_t *timeout, bool interruptible)
> > -{
> > - int ret;
> > -
> > - if (fence > fctx->last_fence) {
> > - DRM_ERROR_RATELIMITED("%s: waiting on invalid fence: %u (of %u)\n",
> > - fctx->name, fence, fctx->last_fence);
> > - return -EINVAL;
>
> Rob, we changed this pre-existing behaviour in this patch. Now, when
> userspace tries to wait on a future fence, we don't return an error.
>
> I just want to check if this was accidental or not?
Hmm, perhaps we should do this to restore the previous behavior:
-------------
diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index 73e827641024..3dd6da56eae6 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -1000,8 +1000,12 @@ static int msm_ioctl_wait_fence(struct
drm_device *dev, void *data,
fence = dma_fence_get_rcu(fence);
mutex_unlock(&queue->lock);
- if (!fence)
- return 0;
+ if (!fence) {
+ struct msm_fence_context *fctx = gpu->rb[queue->ring_nr]->fctx;
+ DRM_ERROR_RATELIMITED("%s: waiting on invalid fence:
%u (of %u)\n",
+ fctx->name, fence, fctx->last_fence);
+ return -EINVAL;
+ }
ret = dma_fence_wait_timeout(fence, true, timeout_to_jiffies(&timeout));
if (ret == 0) {
-------------
BR,
-R
> -Akhil.
>
> > - }
> > -
> > - if (!timeout) {
> > - /* no-wait: */
> > - ret = fence_completed(fctx, fence) ? 0 : -EBUSY;
> > - } else {
> > - unsigned long remaining_jiffies = timeout_to_jiffies(timeout);
> > -
> > - if (interruptible)
> > - ret = wait_event_interruptible_timeout(fctx->event,
> > - fence_completed(fctx, fence),
> > - remaining_jiffies);
> > - else
> > - ret = wait_event_timeout(fctx->event,
> > - fence_completed(fctx, fence),
> > - remaining_jiffies);
> > -
> > - if (ret == 0) {
> > - DBG("timeout waiting for fence: %u (completed: %u)",
> > - fence, fctx->completed_fence);
> > - ret = -ETIMEDOUT;
> > - } else if (ret != -ERESTARTSYS) {
> > - ret = 0;
> > - }
> > - }
> > -
> > - return ret;
> > -}
> > -
> > /* called from workqueue */
> > void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence)
> > {
> > spin_lock(&fctx->spinlock);
> > fctx->completed_fence = max(fence, fctx->completed_fence);
> > spin_unlock(&fctx->spinlock);
> > -
> > - wake_up_all(&fctx->event);
> > }
> >
> > struct msm_fence {
> > diff --git a/drivers/gpu/drm/msm/msm_fence.h b/drivers/gpu/drm/msm/msm_fence.h
> > index 6ab97062ff1a..4783db528bcc 100644
> > --- a/drivers/gpu/drm/msm/msm_fence.h
> > +++ b/drivers/gpu/drm/msm/msm_fence.h
> > @@ -49,7 +49,6 @@ struct msm_fence_context {
> > */
> > volatile uint32_t *fenceptr;
> >
> > - wait_queue_head_t event;
> > spinlock_t spinlock;
> > };
> >
> > @@ -57,8 +56,6 @@ struct msm_fence_context * msm_fence_context_alloc(struct drm_device *dev,
> > volatile uint32_t *fenceptr, const char *name);
> > void msm_fence_context_free(struct msm_fence_context *fctx);
> >
> > -int msm_wait_fence(struct msm_fence_context *fctx, uint32_t fence,
> > - ktime_t *timeout, bool interruptible);
> > void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence);
> >
> > struct dma_fence * msm_fence_alloc(struct msm_fence_context *fctx);
> > diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
> > index da3af702a6c8..e0579abda5b9 100644
> > --- a/drivers/gpu/drm/msm/msm_gem.h
> > +++ b/drivers/gpu/drm/msm/msm_gem.h
> > @@ -320,6 +320,7 @@ struct msm_gem_submit {
> > struct ww_acquire_ctx ticket;
> > uint32_t seqno; /* Sequence number of the submit on the ring */
> > struct dma_fence *fence;
> > + int fence_id; /* key into queue->fence_idr */
> > struct msm_gpu_submitqueue *queue;
> > struct pid *pid; /* submitting process */
> > bool fault_dumped; /* Limit devcoredump dumping to one per submit */
> > diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> > index 4f02fa3c78f9..f6f595aae2c5 100644
> > --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> > +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> > @@ -68,7 +68,14 @@ void __msm_gem_submit_destroy(struct kref *kref)
> > container_of(kref, struct msm_gem_submit, ref);
> > unsigned i;
> >
> > + if (submit->fence_id) {
> > + mutex_lock(&submit->queue->lock);
> > + idr_remove(&submit->queue->fence_idr, submit->fence_id);
> > + mutex_unlock(&submit->queue->lock);
> > + }
> > +
> > dma_fence_put(submit->fence);
> > +
> > put_pid(submit->pid);
> > msm_submitqueue_put(submit->queue);
> >
> > @@ -872,6 +879,20 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
> > goto out;
> > }
> >
> > + /*
> > + * Allocate an id which can be used by WAIT_FENCE ioctl to map back
> > + * to the underlying fence.
> > + */
> > + mutex_lock(&queue->lock);
> > + submit->fence_id = idr_alloc_cyclic(&queue->fence_idr,
> > + submit->fence, 0, INT_MAX, GFP_KERNEL);
> > + mutex_unlock(&queue->lock);
> > + if (submit->fence_id < 0) {
> > + ret = submit->fence_id = 0;
> > + submit->fence_id = 0;
> > + goto out;
> > + }
> > +
> > if (args->flags & MSM_SUBMIT_FENCE_FD_OUT) {
> > struct sync_file *sync_file = sync_file_create(submit->fence);
> > if (!sync_file) {
> > @@ -886,7 +907,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
> >
> > msm_gpu_submit(gpu, submit);
> >
> > - args->fence = submit->fence->seqno;
> > + args->fence = submit->fence_id;
> >
> > msm_reset_syncobjs(syncobjs_to_reset, args->nr_in_syncobjs);
> > msm_process_post_deps(post_deps, args->nr_out_syncobjs,
> > diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> > index 96efcb31e502..579627252540 100644
> > --- a/drivers/gpu/drm/msm/msm_gpu.h
> > +++ b/drivers/gpu/drm/msm/msm_gpu.h
> > @@ -263,6 +263,9 @@ struct msm_gpu_perfcntr {
> > * which set of pgtables do submits jobs associated with the
> > * submitqueue use)
> > * @node: node in the context's list of submitqueues
> > + * @fence_idr: maps fence-id to dma_fence for userspace visible fence
> > + * seqno, protected by submitqueue lock
> > + * @lock: submitqueue lock
> > * @ref: reference count
> > */
> > struct msm_gpu_submitqueue {
> > @@ -272,6 +275,8 @@ struct msm_gpu_submitqueue {
> > int faults;
> > struct msm_file_private *ctx;
> > struct list_head node;
> > + struct idr fence_idr;
> > + struct mutex lock;
> > struct kref ref;
> > };
> >
> > diff --git a/drivers/gpu/drm/msm/msm_submitqueue.c b/drivers/gpu/drm/msm/msm_submitqueue.c
> > index 9e9fec61d629..66f8d0fb38b0 100644
> > --- a/drivers/gpu/drm/msm/msm_submitqueue.c
> > +++ b/drivers/gpu/drm/msm/msm_submitqueue.c
> > @@ -12,6 +12,8 @@ void msm_submitqueue_destroy(struct kref *kref)
> > struct msm_gpu_submitqueue *queue = container_of(kref,
> > struct msm_gpu_submitqueue, ref);
> >
> > + idr_destroy(&queue->fence_idr);
> > +
> > msm_file_private_put(queue->ctx);
> >
> > kfree(queue);
> > @@ -89,6 +91,9 @@ int msm_submitqueue_create(struct drm_device *drm, struct msm_file_private *ctx,
> > if (id)
> > *id = queue->id;
> >
> > + idr_init(&queue->fence_idr);
> > + mutex_init(&queue->lock);
> > +
> > list_add_tail(&queue->node, &ctx->submitqueues);
> >
> > write_unlock(&ctx->queuelock);
> >
>
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