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Sender: Guenter Roeck <groeck7@gmail.com>
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Date:   Wed, 20 Sep 2023 08:18:50 -0700
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To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Kyle Zeng <zengyhkyle@gmail.com>
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        linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
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References: <20230917191101.035638219@linuxfoundation.org>
 <07a04540-554c-4394-1e79-46ea665f8c03@roeck-us.net>
 <2023092009-angriness-sank-ae4f@gregkh>
From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH 5.10 000/406] 5.10.195-rc1 review
In-Reply-To: <2023092009-angriness-sank-ae4f@gregkh>
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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.

Guenter