Patch "drm/amdgpu: fix fence slab teardown" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

drm/amdgpu: fix fence slab teardown

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-amdgpu-fix-fence-slab-teardown.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Grazvydas Ignotas <[email protected]>
Date: Sun, 23 Oct 2016 21:31:43 +0300
Subject: drm/amdgpu: fix fence slab teardown
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From: Grazvydas Ignotas <[email protected]>

commit 0f10425e811355986907c54f7d1d06703e406092 upstream.

To free fences, call_rcu() is used, which calls amdgpu_fence_free() after a grace period. During teardown, there is no guarantee all callbacks have finished, so amdgpu_fence_slab may be destroyed before all fences have been freed. If we are lucky, this results in some slab warnings, if not, we get a crash in one of rcu threads because callback is called after amdgpu has already been unloaded.

Fix it with a rcu_barrier().

---
 drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c |    1 +
 1 file changed, 1 insertion(+)

@@ -68,6 +68,7 @@ int amdgpu_fence_slab_init(void)
 
 void amdgpu_fence_slab_fini(void)
 {
+	rcu_barrier();
 	kmem_cache_destroy(amdgpu_fence_slab);
 }
 /*

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/drm-amdgpu-fix-fence-slab-teardown.patch queue-4.8/drm-amdgpu-fix-sched-fence-slab-teardown.patch queue-4.8/drm-amd-fix-scheduler-fence-teardown-order-v2.patch queue-4.8/drm-amdgpu-fix-a-vm_flush-fence-leak.patch