Re: [PATCH v2 3/3] media: amphion: Remove lock in s_ctrl callback

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Hi Ming,

W dniu 30.04.2024 o 04:32, ming qian pisze:
Hi Andrzej,

Hi Ming Qian,

W dniu 25.04.2024 o 08:50, Ming Qian pisze:
There is no need to add lock in s_ctrl callback, it has been
synchronized by the ctrl_handler's lock, otherwise it may led to
deadlock if driver call v4l2_ctrl_s_ctrl().

Signed-off-by: Ming Qian <ming.qian@xxxxxxx>
  drivers/media/platform/amphion/vdec.c | 2 --
  drivers/media/platform/amphion/venc.c | 2 --
  2 files changed, 4 deletions(-)

diff --git a/drivers/media/platform/amphion/vdec.c b/drivers/media/platform/amphion/vdec.c
index a57f9f4f3b87..6a38a0fa0e2d 100644
--- a/drivers/media/platform/amphion/vdec.c
+++ b/drivers/media/platform/amphion/vdec.c
@@ -195,7 +195,6 @@ static int vdec_op_s_ctrl(struct v4l2_ctrl *ctrl)
      struct vdec_t *vdec = inst->priv;
      int ret = 0;
-    vpu_inst_lock(inst);

I assume that PATCH v2 2/3 might cause the said deadlock to happen?
If so, maybe it would make more sense to make the current patch preceed
  PATCH v2 2/3? Otherwise the kernel at PATCH v2 2/3 introduces a potential



I actually discovered this problem when I was preparing the v2 2/3 patch.

But in the v2 2/3 patch, it tried to add a read-only ctrl, then I just
unset the s_ctrl callback for the new added ctrl, the potential deadlock
is caused by call the s_ctrl back in a locked environment, so after unset
the s_ctrl callback, the 2/3 patch won't trigger the deadlock even if
this patch is missing.

In order to avoid encountering similar problems in the future, that
driver may set or get some ctrl, I added this patch.

Do I understand you correctly that patch 2/3 is written in such a way that
it does not introduce a deadlock, and you add patch 3/3 only to prevent future
problems? If so, it seems to me that patch 3/3 could/should be separate from
this series, as it does not quite match "Add average qp control".



Best regards,

      switch (ctrl->id) {
          vdec->params.display_delay_enable = ctrl->val;
@@ -207,7 +206,6 @@ static int vdec_op_s_ctrl(struct v4l2_ctrl *ctrl)
          ret = -EINVAL;
-    vpu_inst_unlock(inst);
      return ret;
diff --git a/drivers/media/platform/amphion/venc.c b/drivers/media/platform/amphion/venc.c
index cdfaba9d107b..351b4edc8742 100644
--- a/drivers/media/platform/amphion/venc.c
+++ b/drivers/media/platform/amphion/venc.c
@@ -518,7 +518,6 @@ static int venc_op_s_ctrl(struct v4l2_ctrl *ctrl)
      struct venc_t *venc = inst->priv;
      int ret = 0;
-    vpu_inst_lock(inst);
      switch (ctrl->id) {
      case V4L2_CID_MPEG_VIDEO_H264_PROFILE:
          venc->params.profile = ctrl->val;
@@ -579,7 +578,6 @@ static int venc_op_s_ctrl(struct v4l2_ctrl *ctrl)
          ret = -EINVAL;
-    vpu_inst_unlock(inst);
      return ret;

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