Messages in this thread | | | Date | Tue, 30 Apr 2024 16:55:06 +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, > > 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 >
You're right, when I prepare the 2/3 patch, I add the new ctrl just like the previous ctrl, but I got a deadlock. then I tried to fix a deadlock in 2/3 patch first, and make this patch again to avoid similar errors.
I put this patch to this series, as I think this better explains why I made this change.
Regards, Ming
>> >> 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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