drm/amdgpu: hold reference to fences in amdgpu_sa_bo_new (v2)

An arbitrary amount of time can pass between spin_unlock and fence_wait_any_timeout, so we need to ensure that nobody frees the fences from under us. A stress test (rapidly starting and killing hundreds of glxgears instances) ran into a deadlock in fence_wait_any_timeout after about an hour, and this race condition appears to be a plausible cause. v2: agd: rebase on upstream Signed-off-by: Nicolai Hähnle <[email protected]> Reviewed-by: Alex Deucher <[email protected]> Reviewed-by: Christian König <[email protected]> Cc: [email protected]
kyagi · Feb 10, 2016 · a8d81b3 · a8d81b3
1 parent ca19852
commit a8d81b3
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sa.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sa.c
@@ -354,12 +354,15 @@ int amdgpu_sa_bo_new(struct amdgpu_sa_manager *sa_manager,
 
 		for (i = 0, count = 0; i < AMDGPU_MAX_RINGS; ++i)
 			if (fences[i])
-				fences[count++] = fences[i];
+				fences[count++] = fence_get(fences[i]);
 
 		if (count) {
 			spin_unlock(&sa_manager->wq.lock);
 			t = fence_wait_any_timeout(fences, count, false,
 						   MAX_SCHEDULE_TIMEOUT);
+			for (i = 0; i < count; ++i)
+				fence_put(fences[i]);
+
 			r = (t > 0) ? 0 : t;
 			spin_lock(&sa_manager->wq.lock);
 		} else {