[PATCH 5.2 070/124] drm/amdgpu: fix dma_fence_wait without reference

[Greg Kroah-Hartman]

From: Christian König <christian.koe...@amd.com>

[ Upstream commit 42068e1ef961c719f967dbbb4ddcb394a0ba7917 ]

We need to grab a reference to the fence we wait for.

Signed-off-by: Christian König <christian.koe...@amd.com>
Reviewed-by: Chunming Zhou <david1.z...@amd.com>
Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 27 ++++++++++++++-----------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
index a28a3d722ba29..62298ae5c81c0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
@@ -535,21 +535,24 @@ int amdgpu_ctx_wait_prev_fence(struct amdgpu_ctx *ctx,
                               struct drm_sched_entity *entity)
 {
        struct amdgpu_ctx_entity *centity = to_amdgpu_ctx_entity(entity);
-       unsigned idx = centity->sequence & (amdgpu_sched_jobs - 1);
-       struct dma_fence *other = centity->fences[idx];
+       struct dma_fence *other;
+       unsigned idx;
+       long r;
 
-       if (other) {
-               signed long r;
-               r = dma_fence_wait(other, true);
-               if (r < 0) {
-                       if (r != -ERESTARTSYS)
-                               DRM_ERROR("Error (%ld) waiting for fence!\n", 
r);
+       spin_lock(&ctx->ring_lock);
+       idx = centity->sequence & (amdgpu_sched_jobs - 1);
+       other = dma_fence_get(centity->fences[idx]);
+       spin_unlock(&ctx->ring_lock);
 
-                       return r;
-               }
-       }
+       if (!other)
+               return 0;
 
-       return 0;
+       r = dma_fence_wait(other, true);
+       if (r < 0 && r != -ERESTARTSYS)
+               DRM_ERROR("Error (%ld) waiting for fence!\n", r);
+
+       dma_fence_put(other);
+       return r;
 }
 
 void amdgpu_ctx_mgr_init(struct amdgpu_ctx_mgr *mgr)
-- 
2.20.1