[PATCH] drm/amdgpu: Fix the null pointer issue for tdr
Koenig, Christian
Christian.Koenig at amd.com
Fri Nov 8 09:42:32 UTC 2019
Am 08.11.19 um 10:39 schrieb Deng, Emily:
> Sorry, please take your time.
Have you seen my other response a bit below?
I can't follow how it would be possible for job->s_fence to be NULL
without the job also being freed.
So it looks like this patch is just papering over some bigger issues.
Regards,
Christian.
>
> Best wishes
> Emily Deng
>
>
>
>> -----Original Message-----
>> From: Koenig, Christian <Christian.Koenig at amd.com>
>> Sent: Friday, November 8, 2019 5:08 PM
>> To: Deng, Emily <Emily.Deng at amd.com>; amd-gfx at lists.freedesktop.org
>> Subject: Re: [PATCH] drm/amdgpu: Fix the null pointer issue for tdr
>>
>> Am 08.11.19 um 09:52 schrieb Deng, Emily:
>>> Ping.....
>> You need to give me at least enough time to wake up :)
>>
>>>
>>> Best wishes
>>> Emily Deng
>>>
>>>
>>>
>>>> -----Original Message-----
>>>> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
>>>> Deng, Emily
>>>> Sent: Friday, November 8, 2019 10:56 AM
>>>> To: Koenig, Christian <Christian.Koenig at amd.com>; amd-
>>>> gfx at lists.freedesktop.org
>>>> Subject: RE: [PATCH] drm/amdgpu: Fix the null pointer issue for tdr
>>>>
>>>>> -----Original Message-----
>>>>> From: Christian König <ckoenig.leichtzumerken at gmail.com>
>>>>> Sent: Thursday, November 7, 2019 7:28 PM
>>>>> To: Deng, Emily <Emily.Deng at amd.com>; amd-gfx at lists.freedesktop.org
>>>>> Subject: Re: [PATCH] drm/amdgpu: Fix the null pointer issue for tdr
>>>>>
>>>>> Am 07.11.19 um 11:25 schrieb Emily Deng:
>>>>>> When the job is already signaled, the s_fence is freed. Then it
>>>>>> will has null pointer in amdgpu_device_gpu_recover.
>>>>> NAK, the s_fence is only set to NULL when the job is destroyed. See
>>>>> drm_sched_job_cleanup().
>>>> I know it is set to NULL in drm_sched_job_cleanup. But in one case,
>>>> when it enter into the amdgpu_device_gpu_recover, it already in
>>>> drm_sched_job_cleanup, and at this time, it will go to free job. But
>>>> the amdgpu_device_gpu_recover sometimes is faster. At that time, job
>>>> is not freed, but s_fence is already NULL.
>> No, that case can't happen. See here:
>>
>>> drm_sched_job_cleanup(s_job);
>>>
>>> amdgpu_ring_priority_put(ring, s_job->s_priority);
>>> dma_fence_put(job->fence);
>>> amdgpu_sync_free(&job->sync);
>>> amdgpu_sync_free(&job->sched_sync);
>>> kfree(job);
>> The job itself is freed up directly after freeing the reference to the s_fence.
>>
>> So you are just papering over a much bigger problem here. This patch is a
>> clear NAK.
>>
>> Regards,
>> Christian.
>>
>>>>> When you see a job without an s_fence then that means the problem is
>>>>> somewhere else.
>>>>>
>>>>> Regards,
>>>>> Christian.
>>>>>
>>>>>> Signed-off-by: Emily Deng <Emily.Deng at amd.com>
>>>>>> ---
>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>>>>>> drivers/gpu/drm/scheduler/sched_main.c | 11 ++++++-----
>>>>>> 2 files changed, 7 insertions(+), 6 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>> index e6ce949..5a8f08e 100644
>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>> @@ -4075,7 +4075,7 @@ int amdgpu_device_gpu_recover(struct
>>>>> amdgpu_device *adev,
>>>>>> *
>>>>>> * job->base holds a reference to parent fence
>>>>>> */
>>>>>> - if (job && job->base.s_fence->parent &&
>>>>>> + if (job && job->base.s_fence && job->base.s_fence->parent &&
>>>>>> dma_fence_is_signaled(job->base.s_fence->parent))
>>>>>> job_signaled = true;
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c
>>>>>> b/drivers/gpu/drm/scheduler/sched_main.c
>>>>>> index 31809ca..56cc10e 100644
>>>>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>>>>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>>>>>> @@ -334,8 +334,8 @@ void drm_sched_increase_karma(struct
>>>>> drm_sched_job
>>>>>> *bad)
>>>>>>
>>>>>> spin_lock(&rq->lock);
>>>>>> list_for_each_entry_safe(entity, tmp, &rq->entities,
>>>>> list) {
>>>>>> - if (bad->s_fence->scheduled.context ==
>>>>>> - entity->fence_context) {
>>>>>> + if (bad->s_fence && (bad->s_fence-
>>>>>> scheduled.context ==
>>>>>> + entity->fence_context)) {
>>>>>> if (atomic_read(&bad->karma) >
>>>>>> bad->sched->hang_limit)
>>>>>> if (entity->guilty)
>>>>>> @@ -376,7 +376,7 @@ void drm_sched_stop(struct drm_gpu_scheduler
>>>>> *sched, struct drm_sched_job *bad)
>>>>>> * This iteration is thread safe as sched thread is stopped.
>>>>>> */
>>>>>> list_for_each_entry_safe_reverse(s_job, tmp, &sched-
>>>>>> ring_mirror_list, node) {
>>>>>> - if (s_job->s_fence->parent &&
>>>>>> + if (s_job->s_fence && s_job->s_fence->parent &&
>>>>>> dma_fence_remove_callback(s_job->s_fence->parent,
>>>>>> &s_job->cb)) {
>>>>>> atomic_dec(&sched->hw_rq_count); @@ -395,7
>>>> +395,8 @@ void
>>>>>> drm_sched_stop(struct drm_gpu_scheduler
>>>>> *sched, struct drm_sched_job *bad)
>>>>>> *
>>>>>> * Job is still alive so fence refcount at least 1
>>>>>> */
>>>>>> - dma_fence_wait(&s_job->s_fence->finished, false);
>>>>>> + if (s_job->s_fence)
>>>>>> + dma_fence_wait(&s_job->s_fence->finished,
>>>>> false);
>>>>>> /*
>>>>>> * We must keep bad job alive for later use during @@
>>>>> -438,7
>>>>>> +439,7 @@ void drm_sched_start(struct drm_gpu_scheduler *sched,
>>>>>> +bool
>>>>> full_recovery)
>>>>>> * GPU recovers can't run in parallel.
>>>>>> */
>>>>>> list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list,
>>>>>> node)
>>>>> {
>>>>>> - struct dma_fence *fence = s_job->s_fence->parent;
>>>>>> + struct dma_fence *fence = s_job->s_fence ? s_job->s_fence-
>>>>>> parent :
>>>>>> +NULL;
>>>>>>
>>>>>> atomic_inc(&sched->hw_rq_count);
>>>>>>
>>>> _______________________________________________
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