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

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

[gregkh]

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 <stable@vger.kernel.org> know about it.


>From 0f10425e811355986907c54f7d1d06703e406092 Mon Sep 17 00:00:00 2001
From: Grazvydas Ignotas <notasas@gmail.com>
Date: Sun, 23 Oct 2016 21:31:43 +0300
Subject: drm/amdgpu: fix fence slab teardown
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Grazvydas Ignotas <notasas@gmail.com>

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().

Fixes: b44135351a3a ("drm/amdgpu: RCU protected amdgpu_fence_release")
Acked-by: Chunming Zhou <david1.zhou@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -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 notasas@gmail.com 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