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

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Message-ID: <4722265C.7050907@nortel.com>
Date:	Fri, 26 Oct 2007 11:39:40 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Andrew Haley <aph@...hat.com>
CC:	Nick Piggin <nickpiggin@...oo.com.au>, davids@...master.com,
	"Torvalds, Linus" <torvalds@...ux-foundation.org>,
	"Kleen, Andi" <ak@...e.de>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Re: Is gcc thread-unsafe?

Andrew Haley wrote:

> We're listening, really.  It's unacceptable that gcc should break
> code.

In that case a conversion of a conditional branch to an unconditional 
write to a visible variable is not an acceptable behaviour.  Aside from 
the kernel issues, it would break any number of threaded userspace apps.

As was mentioned elsewhere, it's akin to sprinkling

int j = i; i = j;

throughout the code.  If "i" is accessed by multiple threads, this is 
not allowed unless a lock is held.

Chris
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