From: "David S. Miller" <davem@davemloft.net>
To: andrea@suse.de
Cc: herbert@gondor.apana.org.au, nickpiggin@yahoo.com.au,
benh@kernel.crashing.org, hugh@veritas.com, paulus@samba.org,
anton@samba.org, torvalds@osdl.org, akpm@osdl.org,
linux-kernel@vger.kernel.org
Subject: Re: Possible memory ordering bug in page reclaim?
Date: Sat, 15 Oct 2005 16:07:02 -0700 (PDT) [thread overview]
Message-ID: <20051015.160702.128767261.davem@davemloft.net> (raw)
In-Reply-To: <20051015200701.GP18159@opteron.random>
From: Andrea Arcangeli <andrea@suse.de>
Date: Sat, 15 Oct 2005 22:07:01 +0200
> sure see alpha:
>
> __asm__ __volatile__(
> "1: ldq_l %0,%1\n"
> " addq %0,%3,%2\n"
> " addq %0,%3,%0\n"
> " stq_c %0,%1\n"
> " beq %0,2f\n"
> " mb\n"
>
> the memory barrier is applied way after the write is visible to other
> cpus, you can even get an irq before the mb and block there for some
> usec.
For atomic operations returning values, there must be a memory
barrier both before and after the atomic operation. This is
defined in Documentation/atomic_ops.txt, so Alpha needs to be
fixed to add a memory barrier at the beginning of these
assembler sequences.
next prev parent reply other threads:[~2005-10-15 23:07 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-15 3:28 Nick Piggin
2005-10-15 6:17 ` Hugh Dickins
2005-10-15 7:43 ` Benjamin Herrenschmidt
2005-10-15 8:00 ` Herbert Xu
2005-10-15 16:57 ` Linus Torvalds
2005-10-15 19:29 ` David S. Miller
2005-10-15 22:17 ` Benjamin Herrenschmidt
2005-10-16 0:04 ` Nick Piggin
2005-10-15 8:59 ` Nick Piggin
2005-10-15 12:08 ` Herbert Xu
2005-10-15 13:35 ` Nick Piggin
2005-10-15 18:00 ` Andrea Arcangeli
2005-10-15 19:48 ` Herbert Xu
2005-10-15 20:07 ` Andrea Arcangeli
2005-10-15 23:07 ` David S. Miller [this message]
2005-10-16 19:36 ` Ivan Kokshaysky
2005-10-17 4:29 ` David S. Miller
2005-10-17 7:23 ` Ivan Kokshaysky
2005-10-17 11:28 ` Andrea Arcangeli
2005-10-15 22:16 ` Benjamin Herrenschmidt
2005-10-15 23:13 ` David S. Miller
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