From: ming qian <ming.qian@oss.nxp.com>
To: Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
Ming Qian <ming.qian@nxp.com>,
mchehab@kernel.org, hverkuil-cisco@xs4all.nl
Cc: shawnguo@kernel.org, robh+dt@kernel.org, s.hauer@pengutronix.de,
kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com,
xiahong.bao@nxp.com, eagle.zhou@nxp.com, tao.jiang_2@nxp.com,
imx@lists.linux.dev, linux-media@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 3/3] media: amphion: Remove lock in s_ctrl callback
Date: Tue, 30 Apr 2024 16:55:06 +0800 [thread overview]
Message-ID: <84aa4bfb-d3fa-4721-98a2-dad0cc753434@oss.nxp.com> (raw)
In-Reply-To: <0c0e2d02-b719-4f8b-afca-c839bb77f287@collabora.com>
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;
>>>> }
>>>
>
next prev parent reply other threads:[~2024-04-30 8:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-25 6:50 [PATCH v2 1/3] media: v4l2-ctrls: Add average qp control Ming Qian
2024-04-25 6:50 ` [PATCH v2 2/3] media: amphion: Report the average QP of current encoded frame Ming Qian
2024-04-25 6:50 ` [PATCH v2 3/3] media: amphion: Remove lock in s_ctrl callback Ming Qian
2024-04-29 17:44 ` Andrzej Pietrasiewicz
2024-04-30 2:32 ` ming qian
2024-04-30 8:00 ` Andrzej Pietrasiewicz
2024-04-30 8:55 ` ming qian [this message]
2024-04-29 17:38 ` [PATCH v2 1/3] media: v4l2-ctrls: Add average qp control Andrzej Pietrasiewicz
2024-04-30 2:20 ` ming qian
2024-04-30 7:56 ` Andrzej Pietrasiewicz
2024-04-30 8:43 ` ming qian
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