linux-kernel - Re: [PATCH] "volatile considered harmful", take 2

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: <20070511074126.GA3037@titan.lahn.de>
Date:	Fri, 11 May 2007 09:41:26 +0200
From:	Philipp Matthias Hahn <pmhahn@...an.lahn.de>
To:	Jonathan Corbet <corbet@....net>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] "volatile considered harmful", take 2

Hello!

On Thu, May 10, 2007 at 02:20:19PM -0600, Jonathan Corbet wrote:
...
> +++ b/Documentation/volatile-considered-harmful.txt
...
> +Consider a typical block of kernel code:
> +
> +    spin_lock(&the_lock);
> +    do_something_on(&shared_data);
                        ^^^^^^^^^^^
> +    do_something_else_with(&shared_data);
                               ^^^^^^^^^^^
> +    spin_unlock(&the_lock);
> +
> +If all the code follows the locking rules, the value of shared_data cannot
> +change unexpectedly while the_lock is held.  Any other code which might
> +want to play with that data will be waiting on the lock.  The spinlock
> +primitives act as memory barriers - they are explicitly written to do so -
> +meaning that data accesses will not be optimized across them.  So the
> +compiler might think it knows what will be in some_data, but the
s/some_data/shared_data/ ?                       ^^^^^^^^^

BYtE
Philipp
-- 
  / /  (_)__  __ ____  __ Philipp Hahn
 / /__/ / _ \/ // /\ \/ /
/____/_/_//_/\_,_/ /_/\_\ pmhahn@...an.lahn.de
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/