linux-kernel - Re: [PATCH] i2c: core: Workaround false-positive LOCKDEP in delete

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Message-ID: <bbb5d2b0-7fbc-0b7d-d58e-355ef1871a1e@nokia.com>
Date:   Mon, 23 May 2022 09:15:26 +0200
From:   Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:     Wolfram Sang <wsa@...nel.org>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: core: Workaround false-positive LOCKDEP in
 delete_device

Hello Wolfram,

On 21/05/2022 11:50, Wolfram Sang wrote:
>> +			/*
>> +			 * We drop the mutex here, because device unregister
>> +			 * will take sysfs lock (kn->count) which, as LOCKDEP
>> +			 * would think, depends on this mutex
>> +			 */
> I have to ask: can't lockdep be fixed or the lock somehow be annotated
> to prevent the false positive?

I would be happy to test any other proposal, I personally didn't find other working
approach until now. This particular patch actually has an advantage of reducing the
locked region, which makes sense if only userspace_clients is protected by the mutex.

-- 
Best regards,
Alexander Sverdlin.