linux-kernel - Re: [V9fs-developer] [PATCH 4/6] 9p: Remove an unnecessary memory barrier

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180628143323.GA32547@nautica>
Date:   Thu, 28 Jun 2018 16:33:23 +0200
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     v9fs-developer@...ts.sourceforge.net,
        Latchesar Ionkov <lucho@...kov.net>,
        Eric Van Hensbergen <ericvh@...il.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Ron Minnich <rminnich@...dia.gov>
Subject: Re: [V9fs-developer] [PATCH 4/6] 9p: Remove an unnecessary memory
 barrier

Matthew Wilcox wrote on Thu, Jun 28, 2018:
> How about this?
> 
> 	/*
> 	 * This barrier is needed to make sure any change made to req before
> -	 * the other thread wakes up will indeed be seen by the waiting side.
> +	 * the status change is visible to another thread
> 	 */

Yes, that sounds better.

This code is fairly old and I was wondering if the new WRITE_ONCE and
READ_ONCE macros would help but it looks like compile-time barriers only
so I do not think they would be enough...
Documentation/memory-barriers.txt still suggests something similar in
the "SLEEP AND WAKE-UP FUNCTIONS" section so I guess this is fine.


Thanks,
-- 
Dominique Martinet | Asmadeus