[PATCH] Revert "drm/amdgpu: remove ctx->lock"

[Luben Tuikov]

This reverts commit e68efb27647f2106d6b545667f35b2ea39746b57.

We see that the bo validate list gets corrupted, in
amdgpu_cs_list_validate(), the lobj->tv.bo is NULL. Then getting usermm on
the next line, references a NULL bo and we get a koops.

Bisecting leads to the commit being reverted as the cause of the list
corruption. See the link below for details of the corruption failure.

Cc: Christian König <christian.koenig at amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky at amd.com>
Cc: Alex Deucher <Alexander.Deucher at amd.com>
Cc: Vitaly Prosyak <Vitaly.Prosyak at amd.com>
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2048#note_1427539
Signed-off-by: Luben Tuikov <luben.tuikov at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c  | 16 +++++-----------
 drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c |  2 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h |  1 +
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 36ac1f1d11e6b4..e619031753b927 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -128,6 +128,8 @@ static int amdgpu_cs_parser_init(struct amdgpu_cs_parser *p, union drm_amdgpu_cs
 		goto free_chunk;
 	}
 
+	mutex_lock(&p->ctx->lock);
+
 	/* skip guilty context job */
 	if (atomic_read(&p->ctx->guilty) == 1) {
 		ret = -ECANCELED;
@@ -585,16 +587,6 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
 		}
 	}
 
-	/* Move fence waiting after getting reservation lock of
-	 * PD root. Then there is no need on a ctx mutex lock.
-	 */
-	r = amdgpu_ctx_wait_prev_fence(p->ctx, p->entity);
-	if (unlikely(r != 0)) {
-		if (r != -ERESTARTSYS)
-			DRM_ERROR("amdgpu_ctx_wait_prev_fence failed.\n");
-		goto error_validate;
-	}
-
 	amdgpu_cs_get_threshold_for_moves(p->adev, &p->bytes_moved_threshold,
 					  &p->bytes_moved_vis_threshold);
 	p->bytes_moved = 0;
@@ -722,6 +714,7 @@ static void amdgpu_cs_parser_fini(struct amdgpu_cs_parser *parser, int error,
 	dma_fence_put(parser->fence);
 
 	if (parser->ctx) {
+		mutex_unlock(&parser->ctx->lock);
 		amdgpu_ctx_put(parser->ctx);
 	}
 	if (parser->bo_list)
@@ -965,7 +958,7 @@ static int amdgpu_cs_ib_fill(struct amdgpu_device *adev,
 	if (parser->job->uf_addr && ring->funcs->no_user_fence)
 		return -EINVAL;
 
-	return 0;
+	return amdgpu_ctx_wait_prev_fence(parser->ctx, parser->entity);
 }
 
 static int amdgpu_cs_process_fence_dep(struct amdgpu_cs_parser *p,
@@ -1384,6 +1377,7 @@ int amdgpu_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
 		goto out;
 
 	r = amdgpu_cs_submit(&parser, cs);
+
 out:
 	amdgpu_cs_parser_fini(&parser, r, reserved_buffers);
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
index 53f9268366f29e..2ef5296216d64d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
@@ -286,6 +286,7 @@ static int amdgpu_ctx_init(struct amdgpu_ctx_mgr *mgr, int32_t priority,
 	kref_init(&ctx->refcount);
 	ctx->mgr = mgr;
 	spin_lock_init(&ctx->ring_lock);
+	mutex_init(&ctx->lock);
 
 	ctx->reset_counter = atomic_read(&mgr->adev->gpu_reset_counter);
 	ctx->reset_counter_query = ctx->reset_counter;
@@ -400,6 +401,7 @@ static void amdgpu_ctx_fini(struct kref *ref)
 		drm_dev_exit(idx);
 	}
 
+	mutex_destroy(&ctx->lock);
 	kfree(ctx);
 }
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h
index 0fa0e56daf67e9..cc7c8afff4144c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h
@@ -53,6 +53,7 @@ struct amdgpu_ctx {
 	bool				preamble_presented;
 	int32_t				init_priority;
 	int32_t				override_priority;
+	struct mutex			lock;
 	atomic_t			guilty;
 	unsigned long			ras_counter_ce;
 	unsigned long			ras_counter_ue;

base-commit: f4b3c543a2a759ce657de4b6b7e88eaddee85ec2
-- 
2.36.1.74.g277cf0bc36