Messages in this thread | | | Date | Tue, 30 Apr 2024 10:00:39 +0200 | Subject | Re: [PATCH v2 3/3] media: amphion: Remove lock in s_ctrl callback | From | Andrzej Pietrasiewicz <> |
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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@nxp.com> >>> --- >>> 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 >> deadlock. >> >> Regards, >> >> Andrzej >> > > 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".
Regards,
Andrzej
> > Best regards, > Ming > >>> switch (ctrl->id) { >>> case V4L2_CID_MPEG_VIDEO_DEC_DISPLAY_DELAY_ENABLE: >>> vdec->params.display_delay_enable = ctrl->val; >>> @@ -207,7 +206,6 @@ static int vdec_op_s_ctrl(struct v4l2_ctrl *ctrl) >>> ret = -EINVAL; >>> break; >>> } >>> - 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; >>> break; >>> } >>> - vpu_inst_unlock(inst); >>> return ret; >>> } >>
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