From: David Howells <dhowells@redhat.com>
To: Nick Piggin <npiggin@suse.de>
Cc: dhowells@redhat.com,
Linus Torvalds <torvalds@linux-foundation.org>,
Paul McKenney <paulmck@us.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andi Kleen <ak@suse.de>
Subject: Re: [rfc][patch] i386: remove comment about barriers
Date: Mon, 01 Oct 2007 14:14:44 +0100 [thread overview]
Message-ID: <29721.1191244484@redhat.com> (raw)
In-Reply-To: <20070929132848.GA21169@wotan.suse.de>
Nick Piggin <npiggin@suse.de> wrote:
> [ This is true for x86's sfence/lfence, but raises a question about Linux's
> memory barriers. Does anybody expect that a sequence of smp_wmb and smp_rmb
> would ever provide a full smp_mb barrier? I've always assumed no, but I
> don't know if it is actually documented? ]
I think you have to assume that smp_wmb() only orders stores and write
barriers, and that smp_rmb() only orders reads and read barriers.
smp_mb() implies both smp_wmb() and smp_rmb(), but is greater than the
combination of the two.
David
prev parent reply other threads:[~2007-10-01 13:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-29 13:28 [rfc][patch] i386: remove comment about barriers Nick Piggin
2007-09-29 16:11 ` Linus Torvalds
2007-09-29 19:12 ` Davide Libenzi
2007-09-30 12:05 ` Nick Piggin
2007-09-30 3:16 ` Paul E. McKenney
2007-09-30 11:58 ` Nick Piggin
2007-09-30 15:09 ` Andi Kleen
2007-10-01 13:14 ` David Howells [this message]
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