linux-kernel - Re: [PATCH 3/7] usb: mtu3: fix KE at qmu transfer done irq handler

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Message-ID: <3f2ba861-10f1-cc5c-caec-6f798486d9cb@collabora.com>
Date:   Fri, 7 Apr 2023 11:08:43 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Chunfeng Yun (云春峰) 
        <Chunfeng.Yun@...iatek.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Cc:     "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Eddie Hung (洪正鑫) 
        <Eddie.Hung@...iatek.com>,
        Tianping Fang (方天平) 
        <Tianping.Fang@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>
Subject: Re: [PATCH 3/7] usb: mtu3: fix KE at qmu transfer done irq handler

Il 07/04/23 09:59, Chunfeng Yun (云春峰) ha scritto:
> On Mon, 2023-04-03 at 14:31 +0200, AngeloGioacchino Del Regno wrote:
>> External email : Please do not click links or open attachments until
>> you have verified the sender or the content.
>>
>>
>> Il 03/04/23 04:52, Chunfeng Yun ha scritto:
>>> When handle qmu transfer irq, it will unlock @mtu->lock before give
>>> back
>>> request, if another thread hanlde disconnect event at the same
>>> time, and
>>> try to disable ep, it may lock @mtu->lock and free qmu ring, then
>>> qmu
>>> irq hanlder may get a NULL gpd, avoid the KE by checking gpd's
>>> value before
>>
>> KE == Kernel Error? I think you wanted to say KP == Kernel Panic
>> instead.
>>
>> Also, s/hanlder/handler/g.
> Ok, will modify it
>>
>>> handling it.
>>>
>>> e.g.
>>> qmu done irq on cpu0                 thread running on cpu1
>>>
>>> qmu_done_tx()
>>>     handle gpd [0]
>>>       mtu3_requ_complete()        mtu3_gadget_ep_disable()
>>>         unlock @mtu->lock
>>>           give back request         lock @mtu->lock
>>>                                       mtu3_ep_disable()
>>>                                         mtu3_gpd_ring_free()
>>>                                      unlock @mtu->lock
>>>         lock @mtu->lock
>>>       get next gpd [1]
>>>
>>> [1]: goto [0] to handle next gpd, and next gpd may be NULL.
>>
>>   >
>>   > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
>>
>> This is a fix and needs a Fixes tag.
> I usually add Fixes tag when the issue introduced by a patch except the
> original one when the driver applied.
> 

If this patch is a fix for the "original driver", you shall still add a
Fixes tag which advertises that this fixes the first commit, so the driver
was broken from the very beginning.

Thanks,
Angelo.