linux-kernel - Re: Is gcc thread-unsafe?

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Date:	Sun, 4 Nov 2007 16:13:00 +0100
From:	"Bart Van Assche" <bart.vanassche@...il.com>
To:	"Andrew Haley" <aph@...hat.com>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Tomash Brechko" <tomash.brechko@...il.com>
Subject: Re: Is gcc thread-unsafe?

On 11/2/07, Andrew Haley <aph@...hat.com> wrote:
> Bart Van Assche writes:
> > On 10/30/07, Andrew Haley <aph@...hat.com> wrote:
> > > That's what the proposed standard language says, kinda-sorta.  There's
> > > an informal description at
> > > http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2338.html.
> >
> > There is other important information in the cited text. A.o. it is
> > explained that register promotion of potentially shared variables
> > can introduce data races. Or: register promotion can introduce bugs
> > in multithreaded software when compiled with optimization
> > enabled. Are there any register promotion transformations
> > implemented in gcc that can introduce data races in multithreaded
> > software ?
>
> I expect so.  We're going to have to audit this whole enormous code
> base to find them all and take them out.
>
> Note that some of these optimizations have been around since gcc 3.4.

Has it already been decided who will do this audit, and when this
audit will happen ? Has a target date been set when this audit should
be complete, or is the completion of this audit a requirement for the
release of a specific gcc version ?

And if there would exist register promotion transformations in gcc
that can introduce data races, which would be the optimization levels
that enable these transformations ?

Bart Van Assche.
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