linux-kernel - Re: KCSAN: data-race in __jbd2_journal_file_buffer / jbd2_journal_dirty

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Date:   Tue, 6 Apr 2021 18:12:50 +0200
From:   Jan Kara <jack@...e.cz>
To:     Theodore Ts'o <tytso@....edu>
Cc:     Jan Kara <jack@...e.cz>, Hao Sun <sunhao.th@...il.com>,
        jack@...e.com, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: KCSAN: data-race in __jbd2_journal_file_buffer /
 jbd2_journal_dirty_metadata

On Tue 06-04-21 11:01:39, Theodore Ts'o wrote:
> On Tue, Apr 06, 2021 at 02:32:33PM +0200, Jan Kara wrote:
> > And the comment explains, why we do this unreliable check. Again, if we
> > wanted to silence KCSAN, we could use data_race() macro but AFAIU Ted isn't
> > very fond of that annotation.
> 
> I'm not fond of the data_race macro, but I like bogus KCSAN reports
> even less.  My main complaint is if we're going to have to put the
> data_race() macro in place, we're going to need to annotate each
> location with an explanation of why it's there (suppress a KCSAN false
> positive), and why's it's safe.  If it's only one or two places, it'll
> probably be fine.  If it's dozens, then I would say that KCSAN is
> becoming a net negative in terms of making the Linux kernel code
> maintainable.

OK, I'll send you patches for the two I've seen in the last month. We'll
see how many accumulate over time.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR