From: Segher Boessenkool <segher@kernel•crashing.org>
To: Chris Snook <csnook@redhat•com>
Cc: wjiang@resilience•com, wensong@linux-vs•org,
heiko.carstens@de•ibm.com, linux-kernel@vger•kernel.org,
ak@suse•de, cfriesen@nortel•com, netdev@vger•kernel.org,
horms@verge•net.au, akpm@linux-foundation•org,
linux-arch@vger•kernel.org, torvalds@linux-foundation•org,
schwidefsky@de•ibm.com, davem@davemloft•net, zlynx@acm•org,
rpjday@mindspring•com, jesper.juhl@gmail•com
Subject: Re: [PATCH 24/24] document volatile atomic_read() behavior
Date: Thu, 9 Aug 2007 17:59:29 +0200 [thread overview]
Message-ID: <8f6bb8a9e4f2819a161d732bdb6c70c0@kernel.crashing.org> (raw)
In-Reply-To: <20070809142430.GA19817@shell.boston.redhat.com>
> Historically this has been
> +accomplished by declaring the counter itself to be volatile, but the
> +ambiguity of the C standard on the semantics of volatile make this
> practice
> +vulnerable to overly creative interpretation by compilers.
It's even worse when accessing through a volatile casted pointer;
see for example the recent(*) GCC bugs in that area.
(*) Well, not _all_ that recent. No one should be using the 3.x
series anymore, right?
> Explicit
> +casting in atomic_read() ensures consistent behavior across
> architectures
> +and compilers.
Even modulo compiler bugs, what makes you believe that?
Segher
next prev parent reply other threads:[~2007-08-09 16:06 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-09 14:24 [PATCH 24/24] document volatile atomic_read() behavior Chris Snook
2007-08-09 15:59 ` Segher Boessenkool [this message]
2007-08-09 16:26 ` Chris Snook
2007-08-09 19:42 ` Segher Boessenkool
2007-08-09 20:05 ` Chris Snook
2007-08-09 22:34 ` Segher Boessenkool
2007-08-09 20:10 ` Chris Friesen
2007-08-09 22:23 ` Segher Boessenkool
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