Re: [PATCH] drm/amdgpu: fix sched fence slab teardown

[Alex Deucher]

On Mon, Oct 24, 2016 at 5:06 AM, Christian König
 wrote:
> Reviewed-by: Christian König 
>
>
> Am 24.10.2016 um 04:34 schrieb zhoucm1:
>>
>> Acked-by: Chunming Zhou 
>>
>> On 2016年10月24日 02:31, Grazvydas Ignotas wrote:
>>>
>>> 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")
>>> Signed-off-by: Grazvydas Ignotas 
>>> ---
>>>   drivers/gpu/drm/amd/scheduler/gpu_scheduler.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
>>> b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
>>> index 963a24d..910b8d5 100644
>>> --- 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_scheduler *sched)
>>>   {
>>>   if (sched->thread)
>>>   kthread_stop(sched->thread);
>>> +rcu_barrier();
>>>   if (atomic_dec_and_test(_fence_slab_ref))
>>>   kmem_cache_destroy(sched_fence_slab);
>>>   }
>>

Applied.  thanks!

Alex
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Re: [PATCH] drm/amdgpu: fix sched fence slab teardown

[Christian König]

Reviewed-by: Christian König 

Am 24.10.2016 um 04:34 schrieb zhoucm1:

Acked-by: Chunming Zhou 

On 2016年10月24日 02:31, Grazvydas Ignotas wrote:

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")

Signed-off-by: Grazvydas Ignotas 
---
  drivers/gpu/drm/amd/scheduler/gpu_scheduler.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c 
b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c

index 963a24d..910b8d5 100644
--- 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_scheduler *sched)
  {
  if (sched->thread)
  kthread_stop(sched->thread);
+rcu_barrier();
  if (atomic_dec_and_test(_fence_slab_ref))
  kmem_cache_destroy(sched_fence_slab);
  }


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Re: [PATCH] drm/amdgpu: fix sched fence slab teardown

[zhoucm1]

Acked-by: Chunming Zhou 

On 2016年10月24日 02:31, Grazvydas Ignotas wrote:

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")
Signed-off-by: Grazvydas Ignotas 
---
  drivers/gpu/drm/amd/scheduler/gpu_scheduler.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c 
b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
index 963a24d..910b8d5 100644
--- 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_scheduler *sched)
  {
if (sched->thread)
kthread_stop(sched->thread);
+   rcu_barrier();
if (atomic_dec_and_test(_fence_slab_ref))
kmem_cache_destroy(sched_fence_slab);
  }


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[PATCH] drm/amdgpu: fix sched fence slab teardown

[Grazvydas Ignotas]

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")
Signed-off-by: Grazvydas Ignotas 
---
 drivers/gpu/drm/amd/scheduler/gpu_scheduler.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c 
b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
index 963a24d..910b8d5 100644
--- 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_scheduler *sched)
 {
if (sched->thread)
kthread_stop(sched->thread);
+   rcu_barrier();
if (atomic_dec_and_test(_fence_slab_ref))
kmem_cache_destroy(sched_fence_slab);
 }
-- 
2.7.4

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