linux-kernel - Re: [PATCH] tell gcc optimizer to never introduce new data races

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Message-ID: <CA+55aFyY7_=3xt-0KE=-fmb+kLurxkBmh8TZWgDZMi_RVpKBpg@mail.gmail.com>
Date:	Tue, 10 Jun 2014 10:46:22 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Martin Jambor <mjambor@...e.cz>, Petr Mladek <pmladek@...e.cz>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"gcc@....gnu.org" <gcc@....gnu.org>
Subject: Re: [PATCH] tell gcc optimizer to never introduce new data races

On Tue, Jun 10, 2014 at 6:23 AM, Jiri Kosina <jkosina@...e.cz> wrote:
> We have been chasing a memory corruption bug, which turned out to be
> caused by very old gcc (4.3.4), which happily turned conditional load into
> a non-conditional one, and that broke correctness (the condition was met
> only if lock was held) and corrupted memory.

Just out of interest, can you point to the particular kernel code that
caused this? I think that's more interesting than the example program
you show - which I'm sure is really nice for gcc developers as an
example, but from a kernel standpoint I think it's more important to
show the particular problems this caused for the kernel?

            Linus
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