linux-kernel - Re: [PATCH v6, 6/7] media: mediatek: vcodec: prevent kernel crash when scp ipi timeout

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Date:   Wed, 18 May 2022 13:34:13 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     "yunfei.dong@...iatek.com" <yunfei.dong@...iatek.com>,
        Alexandre Courbot <acourbot@...omium.org>,
        Nicolas Dufresne <nicolas@...fresne.ca>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tomasz Figa <tfiga@...gle.com>
Cc:     George Sun <george.sun@...iatek.com>,
        Xiaoyong Lu <xiaoyong.lu@...iatek.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Fritz Koenig <frkoenig@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Irui Wang <irui.wang@...iatek.com>,
        Steve Cho <stevecho@...omium.org>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v6, 6/7] media: mediatek: vcodec: prevent kernel crash
 when scp ipi timeout



On 5/18/22 13:29, yunfei.dong@...iatek.com wrote:
> Dear Hans,
> 
> Thanks for your review.
> On Wed, 2022-05-18 at 11:37 +0200, Hans Verkuil wrote:
>> Hi Yunfei,
>>
>> On 5/13/22 11:25, Yunfei Dong wrote:
>>> When SCP timeout during playing video, kernel crashes with
>>> following
>>> message. It's caused by accessing NULL pointer in
>>> vpu_dec_ipi_handler.
>>> This patch doesn't solve the root cause of NULL pointer, but merely
>>> prevent kernel crashed when encounter the NULL pointer.
>>
>> Is the root cause being addressed as well? Where is the root cause?
>> Is it
>> in this driver or in the scp (i.e. the remoteproc) driver?
>>
>> I need a bit more information to decide whether this series is ready
>> to
>> be merged for 5.20 or not.
>>
>> Regards,
>>
>> 	Hans
>>
> Vpu will be NUll when scp(micro processor) is hang or crash. Need to
> keep kernel works well , so add this patch.

OK, I think this should be stated in the commit log, and also in the code
(see below).

> 
> Best Regards,
> Yunfei Dong

<snip>

>>> diff --git a/drivers/media/platform/mediatek/vcodec/vdec_vpu_if.c
>>> b/drivers/media/platform/mediatek/vcodec/vdec_vpu_if.c
>>> index 35f4d5583084..1041dd663e76 100644
>>> --- a/drivers/media/platform/mediatek/vcodec/vdec_vpu_if.c
>>> +++ b/drivers/media/platform/mediatek/vcodec/vdec_vpu_if.c
>>> @@ -91,6 +91,11 @@ static void vpu_dec_ipi_handler(void *data,
>>> unsigned int len, void *priv)
>>>  	struct vdec_vpu_inst *vpu = (struct vdec_vpu_inst *)
>>>  					(unsigned long)msg-
>>>> ap_inst_addr;
>>>  
>>> +	if (!vpu) {
>>> +		mtk_v4l2_err("ap_inst_addr is NULL");

E.g., either add a comment here or perhaps change the error message to:

"ap_inst_addr is NULL, did the SCP hang?"

Or something along those lines.

Shouldn't there be a \n at the end of this message as well? Or does
mtk_v4l2_err add that?

Regards,

	Hans

>>> +		return;
>>> +	}
>>> +
>>>  	mtk_vcodec_debug(vpu, "+ id=%X", msg->msg_id);
>>>  
>>>  	vpu->failure = msg->status;
>