[PATCH v3 1/4] drm/amdgpu/vcn: fix race condition issue for vcn start

[James Zhu]

On 2020-03-11 7:38 a.m., Christian König wrote:
> Am 11.03.20 um 12:30 schrieb Zhu, James:
>>
>> [AMD Official Use Only - Internal Distribution Only]
>>
>>
>> ping
>>
>> ------------------------------------------------------------------------
>> *From:* Zhu, James <James.Zhu at amd.com>
>> *Sent:* Monday, March 9, 2020 12:57 PM
>> *To:* amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
>> *Cc:* Zhu, James <James.Zhu at amd.com>; Koenig, Christian 
>> <Christian.Koenig at amd.com>
>> *Subject:* [PATCH v3 1/4] drm/amdgpu/vcn: fix race condition issue 
>> for vcn start
>> Fix race condition issue when multiple vcn starts are called.
>>
>> v2: Removed checking the return value of cancel_delayed_work_sync()
>> to prevent possible races here.
>>
>> v3: Add total_submission_cnt to avoid gate power unexpectedly.
>>
>> Signed-off-by: James Zhu <James.Zhu at amd.com>
>> ---
>>  drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c | 22 +++++++++++++++-------
>>  drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h |  2 ++
>>  2 files changed, 17 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
>> index a41272f..6aafda1 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
>> @@ -63,6 +63,8 @@ int amdgpu_vcn_sw_init(struct amdgpu_device *adev)
>>          int i, r;
>>
>> INIT_DELAYED_WORK(&adev->vcn.idle_work, amdgpu_vcn_idle_work_handler);
>> + mutex_init(&adev->vcn.vcn_pg_lock);
>> + atomic_set(&adev->vcn.total_submission_cnt, 0);
>>
>>          switch (adev->asic_type) {
>>          case CHIP_RAVEN:
>> @@ -210,6 +212,7 @@ int amdgpu_vcn_sw_fini(struct amdgpu_device *adev)
>>          }
>>
>>          release_firmware(adev->vcn.fw);
>> + mutex_destroy(&adev->vcn.vcn_pg_lock);
>>
>>          return 0;
>>  }
>> @@ -307,7 +310,8 @@ static void amdgpu_vcn_idle_work_handler(struct 
>> work_struct *work)
>>                  fences += fence[j];
>>          }
>>
>> -       if (fences == 0) {
>> +       if (fences == 0 &&
>> + likely(atomic_read(&adev->vcn.total_submission_cnt) == 0)) {
>>                  amdgpu_gfx_off_ctrl(adev, true);
>> amdgpu_device_ip_set_powergating_state(adev, AMD_IP_BLOCK_TYPE_VCN,
>>                         AMD_PG_STATE_GATE);
>> @@ -319,13 +323,14 @@ static void amdgpu_vcn_idle_work_handler(struct 
>> work_struct *work)
>>  void amdgpu_vcn_ring_begin_use(struct amdgpu_ring *ring)
>>  {
>>          struct amdgpu_device *adev = ring->adev;
>> -       bool set_clocks = 
>> !cancel_delayed_work_sync(&adev->vcn.idle_work);
>>
>> -       if (set_clocks) {
>> -               amdgpu_gfx_off_ctrl(adev, false);
>> - amdgpu_device_ip_set_powergating_state(adev, AMD_IP_BLOCK_TYPE_VCN,
>> -                      AMD_PG_STATE_UNGATE);
>> -       }
>> + atomic_inc(&adev->vcn.total_submission_cnt);
>> + cancel_delayed_work_sync(&adev->vcn.idle_work);
>> +
>> + mutex_lock(&adev->vcn.vcn_pg_lock);
>> +       amdgpu_gfx_off_ctrl(adev, false);
>> + amdgpu_device_ip_set_powergating_state(adev, AMD_IP_BLOCK_TYPE_VCN,
>> +              AMD_PG_STATE_UNGATE);
>>
>>          if (adev->pg_flags & AMD_PG_SUPPORT_VCN_DPG)    {
>>                  struct dpg_pause_state new_state;
>> @@ -345,11 +350,14 @@ void amdgpu_vcn_ring_begin_use(struct 
>> amdgpu_ring *ring)
>>
>> adev->vcn.pause_dpg_mode(adev, ring->me, &new_state);
>>          }
>> + mutex_unlock(&adev->vcn.vcn_pg_lock);
>>  }
>>
>>  void amdgpu_vcn_ring_end_use(struct amdgpu_ring *ring)
>>  {
>> schedule_delayed_work(&ring->adev->vcn.idle_work, VCN_IDLE_TIMEOUT);
>> +       if 
>> (unlikely(atomic_dec_return(&ring->adev->vcn.total_submission_cnt) < 0))
>> + atomic_set(&ring->adev->vcn.total_submission_cnt, 0);
>
> You need to decrement first and then call schedule_delayed_work() 
> otherwise the work could run with the wrong counter.
>
> And the extra check for an under run should be superfluous.

Thanks! Please check V4

James

>
> Regards,
> Christian.
>
>>  }
>>
>>  int amdgpu_vcn_dec_ring_test_ring(struct amdgpu_ring *ring)
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h
>> index 6fe0573..111c4cc 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h
>> @@ -200,6 +200,8 @@ struct amdgpu_vcn {
>>          struct drm_gpu_scheduler 
>> *vcn_dec_sched[AMDGPU_MAX_VCN_INSTANCES];
>>          uint32_t num_vcn_enc_sched;
>>          uint32_t num_vcn_dec_sched;
>> +       struct mutex             vcn_pg_lock;
>> +       atomic_t total_submission_cnt;
>>
>>          unsigned        harvest_config;
>>          int (*pause_dpg_mode)(struct amdgpu_device *adev,
>> -- 
>> 2.7.4
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/amd-gfx/attachments/20200311/6a06d7d3/attachment-0001.htm>