From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC] should VM_BUG_ON(cond) really evaluate cond
Date: Thu, 27 Oct 2011 18:34:48 -0700 [thread overview]
Message-ID: <CA+55aFy9oJSK99K=brRzSfSnLocO=PuS7yuKkAcw3t5hATJrfw@mail.gmail.com> (raw)
In-Reply-To: <20111028012521.GF25795@one.firstfloor.org>
On Thu, Oct 27, 2011 at 6:25 PM, Andi Kleen <andi@firstfloor.org> wrote:
>
> Seems reasonable too. In fact we usually should have memory barriers
> for this anyways which obsolete the volatile.
No we shouldn't. Memory barriers are insanely expensive, and pointless
for atomics - that aren't ordered anyway.
You may mean compiler barriers.
That said, removing the volatile entirely might be a good idea, and
never mind any barriers at all. The ordering for atomics really isn't
well enough specified that we should care. So I wouldn't object to a
patch that just removes the volatile entirely, but it would have to be
accompanied with quite a bit of testing, in case some odd case ends up
depending on it. But nothing *should* be looping on those things
anyway.
Linus
next prev parent reply other threads:[~2011-10-28 1:34 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-28 1:19 [RFC] should VM_BUG_ON(cond) really evaluate cond Eric Dumazet
2011-10-28 1:25 ` Andi Kleen
2011-10-28 1:34 ` Linus Torvalds [this message]
2011-10-28 1:44 ` Ben Hutchings
2011-10-28 2:52 ` Eric Dumazet
2011-10-28 3:29 ` Ben Hutchings
2011-10-28 4:43 ` >Re: " Eric Dumazet
2011-10-28 11:37 ` Linus Torvalds
2011-10-28 12:09 ` Eric Dumazet
2011-10-28 12:19 ` Linus Torvalds
2011-10-28 12:40 ` Linus Torvalds
2011-10-28 14:47 ` Eric Dumazet
2011-10-28 14:55 ` Linus Torvalds
2011-10-29 15:43 ` Eric Dumazet
2011-10-29 17:34 ` Linus Torvalds
2011-10-30 8:52 ` Eric Dumazet
2011-10-30 9:59 ` Andi Kleen
2011-10-30 15:16 ` Eric Dumazet
2011-10-30 17:07 ` Linus Torvalds
2011-10-30 17:41 ` Eric Dumazet
2011-10-30 17:48 ` Linus Torvalds
2011-10-30 17:59 ` Eric Dumazet
2011-10-30 18:09 ` Linus Torvalds
2011-11-02 0:14 ` Eric Dumazet
2011-11-01 4:06 ` Stephen Rothwell
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