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

Patch "drm/amdgpu: fix sched 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 sched 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-sched-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 a053fb7e512c77f0742bceb578b10025256e1911 Mon Sep 17 00:00:00 2001
From: Grazvydas Ignotas <notasas@gmail.com>
Date: Sun, 23 Oct 2016 21:31:44 +0300
Subject: drm/amdgpu: fix sched 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 a053fb7e512c77f0742bceb578b10025256e1911 upstream.

To free fences, call_rcu() is used, which calls amd_sched_fence_free()
after a grace period. During teardown, there is no guarantee all
callbacks have finished, so sched_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: 189e0fb76304 ("drm/amdgpu: RCU protected amd_sched_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/scheduler/gpu_scheduler.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
+++ b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
@@ -645,6 +645,7 @@ void amd_sched_fini(struct amd_gpu_sched
 {
 	if (sched->thread)
 		kthread_stop(sched->thread);
+	rcu_barrier();
 	if (atomic_dec_and_test(&sched_fence_slab_ref))
 		kmem_cache_destroy(sched_fence_slab);
 }


Patches currently in stable-queue which might be from notasas@gmail.com are

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