Messages in this thread | | | Date | Tue, 30 Apr 2024 10:32:58 +0800 | Subject | Re: [PATCH v2 3/3] media: amphion: Remove lock in s_ctrl callback | From | ming qian <> |
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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.
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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