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

[James Zhu <jamesz@xxxxxxx>]

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@xxxxxxx>
Sent: Monday, March 9, 2020 12:57 PM
To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>
Cc: Zhu, James <James.Zhu@xxxxxxx>; Koenig, Christian <Christian.Koenig@xxxxxxx>
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@xxxxxxx>
---
 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

_______________________________________________
amd-gfx mailing list
amd-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/amd-gfx