linux-kernel - Re: [PATCH 5.10 000/406] 5.10.195-rc1 review

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Date:   Wed, 20 Sep 2023 10:01:55 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kyle Zeng <zengyhkyle@...il.com>
Cc:     stable@...r.kernel.org, patches@...ts.linux.dev,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        akpm@...ux-foundation.org, shuah@...nel.org, patches@...nelci.org,
        lkft-triage@...ts.linaro.org, pavel@...x.de, jonathanh@...dia.com,
        sudipm.mukherjee@...il.com, srw@...dewatkins.net, rwarsow@....de,
        conor@...nel.org
Subject: Re: [PATCH 5.10 000/406] 5.10.195-rc1 review

On 9/20/23 08:18, Guenter Roeck wrote:
> On 9/20/23 01:11, Greg Kroah-Hartman wrote:
>> On Tue, Sep 19, 2023 at 09:57:25PM -0700, Guenter Roeck wrote:
>>> On 9/17/23 12:07, Greg Kroah-Hartman wrote:
>>>> This is the start of the stable review cycle for the 5.10.195 release.
>>>> There are 406 patches in this series, all will be posted as a response
>>>> to this one.  If anyone has any issues with these being applied, please
>>>> let me know.
>>>>
>>>> Responses should be made by Tue, 19 Sep 2023 19:10:04 +0000.
>>>> Anything received after that time might be too late.
>>>>
>>>
>>> chromeos-5.10 locks up in configfs_lookup() after the merge of 
>>> v5.10.195.
>>>
>>> I am a bit puzzled because I see
>>>
>>> c709c7ca020a configfs: fix a race in configfs_lookup()
>>>
>>> in v5.10.195 but not in the list of commits below. I guess I must be
>>> missing something.
>>
>> It was part of the big patchset, it was posted here:
>>     https://lore.kernel.org/r/20230917191101.511939651@linuxfoundation.org
>>
>> Not hidden at all :)
>>
>> and was submitted here:
>>     https://lore.kernel.org/r/ZPOZFHHA0abVmGx+@westworld
>>
>>> Either case, the code now looks as follows.
>>>
>>> configfs_lookup()
>>> {
>>>      ...
>>>      spin_lock(&configfs_dirent_lock);
>>>      ...
>>>          err = configfs_attach_attr(sd, dentry);
>>>      ...
>>>      spin_unlock(&configfs_dirent_lock);
>>>      ...
>>> }
>>>
>>> and
>>>
>>> configfs_attach_attr(...)
>>> {
>>>      ...
>>>      spin_lock(&configfs_dirent_lock);
>>>      ...
>>> }
>>>
>>> which unless it is way too late here and I really need to go to sleep
>>> just won't work.
>>
>> Kyle, you did the backport, any comments?
>>
> 
> After a good night sleep, the code still looks wrong to me. Reverting
> the offending patch in chromeos-5.10 solved the problem there.
> That makes me suspect that no one actually tests configfs.

Humm indeed, looking at our testing we don't have our USB devices being 
tested which would exercise configfs since we switch the USB device 
between different configurations (mass storage, serial, networking 
etc.). Let me see about adding that so we get some coverage.
-- 
Florian