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

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Message-ID: <YGx308zQXxOjmwNZ@mit.edu>
Date:   Tue, 6 Apr 2021 11:01:39 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     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, 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.

						- Ted