linux-kernel - Re: padata: Is padata_find

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Message-ID: <aQxqTiUUrDmF5M_X@gondor.apana.org.au>
Date: Thu, 6 Nov 2025 17:28:46 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc: syzbot <syzbot+bd936ccd4339cea66e6b@...kaller.appspotmail.com>,
	daniel.m.jordan@...cle.com, linux-kernel@...r.kernel.org,
	steffen.klassert@...unet.com, linux-crypto@...r.kernel.org
Subject: Re: padata: Is padata_find_next() thread-safe?

On Tue, Nov 04, 2025 at 08:44:53PM +0900, Tetsuo Handa wrote:
> syzbot is reporting possibility of recursive locking at
> https://syzkaller.appspot.com/bug?extid=bd936ccd4339cea66e6b .
> If this is a false positive report, the fix will be as simple as

Yes it's a false positive as reorder->lock is never the same as
squeue->serial.lock.

However, they both have the same data type which is why lockdep
is confused.

Please provide a patch that sets the class for one of them to
something different.  For example, change the lockdep class for
reorder->lock using lockdep_set_class and the problem should go
away.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt