[PATCH v2 2/2] drm/amdgpu: Move old fence waiting before reservation lock is aquired.

[Liu, Monk]

Hi Andrey & Christian 

Do we really need the mutext lock here?
Libdrm_amdgpu already has the pthread_mutext to protect multi-thread racing issues, kernel side should be safe with that 

BR Monk

-----Original Message-----
From: Andrey Grodzovsky [mailto:andrey.grodzovsky at amd.com] 
Sent: Wednesday, October 11, 2017 4:50 AM
To: Koenig, Christian <Christian.Koenig at amd.com>; Liu, Monk <Monk.Liu at amd.com>; amd-gfx at lists.freedesktop.org
Cc: Grodzovsky, Andrey <Andrey.Grodzovsky at amd.com>
Subject: [PATCH v2 2/2] drm/amdgpu: Move old fence waiting before reservation lock is aquired.

Helps avoiding deadlock during GPU reset.
Added mutex to amdgpu_ctx to preserve order of fences on a ring.

v2:
Put waiting logic in a function in a seperate function in amdgpu_ctx.c

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h     |  4 ++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c  |  8 ++++++--  drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 30 ++++++++++++++++++++++++------
 3 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index da48f97..235eca5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -741,6 +741,7 @@ struct amdgpu_ctx {
 	bool 			preamble_presented;
 	enum amd_sched_priority init_priority;
 	enum amd_sched_priority override_priority;
+	struct mutex            lock;
 };
 
 struct amdgpu_ctx_mgr {
@@ -763,9 +764,12 @@ void amdgpu_ctx_priority_override(struct amdgpu_ctx *ctx,  int amdgpu_ctx_ioctl(struct drm_device *dev, void *data,
 		     struct drm_file *filp);
 
+int amdgpu_ctx_wait_prev_fence(struct amdgpu_ctx *ctx, unsigned 
+ring_id);
+
 void amdgpu_ctx_mgr_init(struct amdgpu_ctx_mgr *mgr);  void amdgpu_ctx_mgr_fini(struct amdgpu_ctx_mgr *mgr);
 
+
 /*
  * file private structure
  */
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 1a54e53..c36297c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -90,6 +90,8 @@ static int amdgpu_cs_parser_init(struct amdgpu_cs_parser *p, void *data)
 		goto free_chunk;
 	}
 
+	mutex_lock(&p->ctx->lock);
+
 	/* get chunks */
 	chunk_array_user = u64_to_user_ptr(cs->in.chunks);
 	if (copy_from_user(chunk_array, chunk_array_user, @@ -737,8 +739,10 @@ static void amdgpu_cs_parser_fini(struct amdgpu_cs_parser *parser, int error,
 
 	dma_fence_put(parser->fence);
 
-	if (parser->ctx)
+	if (parser->ctx) {
+		mutex_unlock(&parser->ctx->lock);
 		amdgpu_ctx_put(parser->ctx);
+	}
 
 	if (parser->bo_list)
 		amdgpu_bo_list_put(parser->bo_list);
@@ -992,7 +996,7 @@ static int amdgpu_cs_ib_fill(struct amdgpu_device *adev,
 	    parser->job->ring->funcs->type == AMDGPU_RING_TYPE_VCE))
 		return -EINVAL;
 
-	return 0;
+	return amdgpu_ctx_wait_prev_fence(parser->ctx, 
+parser->job->ring->idx);
 }
 
 static int amdgpu_cs_process_fence_dep(struct amdgpu_cs_parser *p, diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
index a78b03f6..4309820 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
@@ -67,6 +67,8 @@ static int amdgpu_ctx_init(struct amdgpu_device *adev,
 	if (!ctx->fences)
 		return -ENOMEM;
 
+	mutex_init(&ctx->lock);
+
 	for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
 		ctx->rings[i].sequence = 1;
 		ctx->rings[i].fences = &ctx->fences[amdgpu_sched_jobs * i]; @@ -126,6 +128,8 @@ static void amdgpu_ctx_fini(struct amdgpu_ctx *ctx)
 				      &ctx->rings[i].entity);
 
 	amdgpu_queue_mgr_fini(adev, &ctx->queue_mgr);
+
+	mutex_destroy(&ctx->lock);
 }
 
 static int amdgpu_ctx_alloc(struct amdgpu_device *adev, @@ -296,12 +300,8 @@ int amdgpu_ctx_add_fence(struct amdgpu_ctx *ctx, struct amdgpu_ring *ring,
 
 	idx = seq & (amdgpu_sched_jobs - 1);
 	other = cring->fences[idx];
-	if (other) {
-		signed long r;
-		r = dma_fence_wait_timeout(other, true, MAX_SCHEDULE_TIMEOUT);
-		if (r < 0)
-			return r;
-	}
+	if (other)
+		BUG_ON(!dma_fence_is_signaled(other));
 
 	dma_fence_get(fence);
 
@@ -372,6 +372,24 @@ void amdgpu_ctx_priority_override(struct amdgpu_ctx *ctx,
 	}
 }
 
+int amdgpu_ctx_wait_prev_fence(struct amdgpu_ctx *ctx, unsigned 
+ring_id) {
+	struct amdgpu_ctx_ring *cring = &ctx->rings[ring_id];
+	unsigned idx = cring->sequence & (amdgpu_sched_jobs - 1);
+	struct dma_fence *other = cring->fences[idx];
+
+	if (other) {
+		signed long r;
+		r = dma_fence_wait_timeout(other, false, MAX_SCHEDULE_TIMEOUT);
+		if (r < 0) {
+			DRM_ERROR("Error (%ld) waiting for fence!\n", r);
+			return r;
+		}
+	}
+
+	return 0;
+}
+
 void amdgpu_ctx_mgr_init(struct amdgpu_ctx_mgr *mgr)  {
 	mutex_init(&mgr->lock);
--
2.7.4