linux-kernel - RE: [EXT] Re: [PATCH] media: amphion: check and cancel vpu before release

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Date:   Mon, 21 Nov 2022 01:59:00 +0000
From:   Ming Qian <ming.qian@....com>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        "mchehab@...nel.org" <mchehab@...nel.org>
CC:     "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "X.H. Bao" <xiahong.bao@....com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [EXT] Re: [PATCH] media: amphion: check and cancel vpu before
 release

>Hi Ming,
>
>On 11/1/22 09:05, Ming Qian wrote:
>> driver need to cancel vpu before releasing the vpu instance, but it
>> doesn't want to release the m2m_ctx before the release callback of
>> instance is called, as driver may access the m2m_ctx in handling some
>> event which may be received in releasing instance.
>>
>> check and cancel the unstopped instance before release.
>>
>> Fixes: d91d7bc85062 ("media: amphion: release m2m ctx when releasing
>> vpu instance")
>> Signed-off-by: Ming Qian <ming.qian@....com>
>> ---
>>  drivers/media/platform/amphion/vpu_v4l2.c | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>
>> diff --git a/drivers/media/platform/amphion/vpu_v4l2.c
>> b/drivers/media/platform/amphion/vpu_v4l2.c
>> index 99ad2f1c5a53..845fc53d8937 100644
>> --- a/drivers/media/platform/amphion/vpu_v4l2.c
>> +++ b/drivers/media/platform/amphion/vpu_v4l2.c
>> @@ -767,6 +767,23 @@ int vpu_v4l2_open(struct file *file, struct vpu_inst
>*inst)
>>       return ret;
>>  }
>>
>> +static void vpu_v4l2_check_and_cancel(struct file *file, struct
>> +vpu_inst *inst) {
>> +     struct vb2_queue *vq;
>> +
>> +     vpu_inst_lock(inst);
>> +
>> +     vq = v4l2_m2m_get_src_vq(inst->fh.m2m_ctx);
>> +     if (vb2_is_streaming(vq))
>> +             v4l2_m2m_streamoff(file, inst->fh.m2m_ctx, vq->type);
>> +
>> +     vq = v4l2_m2m_get_dst_vq(inst->fh.m2m_ctx);
>> +     if (vb2_is_streaming(vq))
>> +             v4l2_m2m_streamoff(file, inst->fh.m2m_ctx, vq->type);
>> +
>> +     vpu_inst_unlock(inst);
>
>This feels weird. This is normally done in v4l2_m2m_ctx_release(), so if you
>need to do this here, doesn't that mean perhaps that the order of releasing
>things should be changed? I.e., first call v4l2_m2m_ctx_release() and only
>afterwards release the vpu instance.
>
>In other words, are you just fixing the symptom rather than the actual cause?
>
>Regards,
>
>        Hans
>

Hi Hans,
    I agree,
    In the first  I indeed call v4l2_m2m_ctx_release() and afterwards release the vpu instance,
But there may be some redundant event triggered by firmware. And they may led to kernel panic as I didn't put the whole event handler into the instance lock.

I just thought if I release the m2m ctx in releasing vpu instance, then thus case can be avoided. But it's really not well thought out.

I'll revert the patch " media: amphion: release m2m ctx when releasing vpu instance", then check the event handler carefully to make sure there is no issue if the m2m ctx has been fixed.

Ming


>> +}
>> +
>>  int vpu_v4l2_close(struct file *file)  {
>>       struct vpu_dev *vpu = video_drvdata(file); @@ -774,6 +791,7 @@
>> int vpu_v4l2_close(struct file *file)
>>
>>       vpu_trace(vpu->dev, "tgid = %d, pid = %d, inst = %p\n",
>> inst->tgid, inst->pid, inst);
>>
>> +     vpu_v4l2_check_and_cancel(file, inst);
>>       call_void_vop(inst, release);
>>       vpu_inst_unregister(inst);
>>       vpu_inst_put(inst);