Re: [RFC 09/17] drm/amdgpu: use dma-fence annotations in cs_submit()

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Am 12.05.20 um 10:59 schrieb Daniel Vetter:
This is a bit tricky, since ->notifier_lock is held while calling
dma_fence_wait we must ensure that also the read side (i.e.
dma_fence_begin_signalling) is on the same side. If we mix this up
lockdep complaints, and that's again why we want to have these
annotations.

A nice side effect of this is that because of the fs_reclaim priming
for dma_fence_enable lockdep now automatically checks for us that
nothing in here allocates memory, without even running any userptr
workloads.

Cc: linux-media@xxxxxxxxxxxxxxx
Cc: linaro-mm-sig@xxxxxxxxxxxxxxxx
Cc: linux-rdma@xxxxxxxxxxxxxxx
Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 5 +++++
  1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 7653f62b1b2d..6db3f3c629b0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1213,6 +1213,7 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
  	struct amdgpu_job *job;
  	uint64_t seq;
  	int r;
+	bool fence_cookie;
job = p->job;
  	p->job = NULL;
@@ -1227,6 +1228,8 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
  	 */
  	mutex_lock(&p->adev->notifier_lock);
+ fence_cookie = dma_fence_begin_signalling();
+
  	/* If userptr are invalidated after amdgpu_cs_parser_bos(), return
  	 * -EAGAIN, drmIoctl in libdrm will restart the amdgpu_cs_ioctl.
  	 */
@@ -1264,12 +1267,14 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
  	amdgpu_vm_move_to_lru_tail(p->adev, &fpriv->vm);
ttm_eu_fence_buffer_objects(&p->ticket, &p->validated, p->fence);
+	dma_fence_end_signalling(fence_cookie);

Mhm, this could come earlier in theory. E.g. after pushing the job to the scheduler.

Christian.

  	mutex_unlock(&p->adev->notifier_lock);
return 0; error_abort:
  	drm_sched_job_cleanup(&job->base);
+	dma_fence_end_signalling(fence_cookie);
  	mutex_unlock(&p->adev->notifier_lock);
error_unlock:

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