From: "H. Peter Anvin" <hpa@zytor.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Nick Piggin <npiggin@suse.de>,
Xen-devel <xen-devel@lists.xensource.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Peter Zijlstra <peterz@infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Jan Beulich <JBeulich@novell.com>, Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH RFC 03/12] x86/ticketlock: Use C for __ticket_spin_unlock
Date: Fri, 06 Aug 2010 10:47:23 -0700 [thread overview]
Message-ID: <4C5C4AAB.3000606@zytor.com> (raw)
In-Reply-To: <4C45CC02.7030603@goop.org>
On 07/20/2010 09:17 AM, Jeremy Fitzhardinge wrote:
>
> "volatile" would be a compiler barrier, but it has no direct effect on,
> or relevence to, the CPU. It just cares about the LOCK_PREFIX. The
> "memory" clobber is probably unnecessary as well, since the constraints
> already tell the compiler the most important information. We can add
> barriers separately as needed.
>
You absolutely need volatile, since otherwise you're permitting the
compiler to split, re-execute or even drop the code. Anything else
might work, by accident, but it's not clean.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2010-08-06 17:47 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-17 1:03 [PATCH RFC 00/12] X86 ticket lock cleanups and improvements Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 02/12] x86/ticketlock: convert spin loop to C Jeremy Fitzhardinge
2010-08-02 15:07 ` Peter Zijlstra
2010-08-02 15:17 ` Jeremy Fitzhardinge
2010-08-06 12:43 ` Jan Beulich
2010-08-06 14:53 ` Jeremy Fitzhardinge
2010-08-06 20:17 ` H. Peter Anvin
2010-08-06 20:33 ` Jeremy Fitzhardinge
2010-08-06 21:09 ` H. Peter Anvin
2010-08-06 22:03 ` Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 06/12] x86/ticketlock: make __ticket_spin_trylock common Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 04/12] x86/ticketlock: make large and small ticket versions of spin_lock the same Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 05/12] x86/ticketlock: make __ticket_spin_lock common Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 09/12] xen/pvticketlock: Xen implementation for PV ticket locks Jeremy Fitzhardinge
2010-09-26 11:39 ` Srivatsa Vaddagiri
2010-09-26 22:34 ` Jeremy Fitzhardinge
2011-01-18 16:27 ` Srivatsa Vaddagiri
2011-01-19 1:28 ` Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 12/12] x86/pvticketlock: use callee-save for unlock_kick as well Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 01/12] x86/ticketlock: clean up types and accessors Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 08/12] x86/ticketlock: collapse a layer of functions Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 10/12] x86/pvticketlock: keep count of blocked cpus Jeremy Fitzhardinge
2010-08-03 8:32 ` Peter Zijlstra
2010-08-03 9:44 ` Nick Piggin
2010-08-03 15:45 ` Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 07/12] x86/spinlocks: replace pv spinlocks with pv ticketlocks Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 03/12] x86/ticketlock: Use C for __ticket_spin_unlock Jeremy Fitzhardinge
2010-07-20 15:38 ` Konrad Rzeszutek Wilk
2010-07-20 16:17 ` Jeremy Fitzhardinge
2010-08-06 17:47 ` H. Peter Anvin [this message]
2010-08-06 20:03 ` Jeremy Fitzhardinge
2010-07-17 1:03 ` [PATCH RFC 11/12] x86/pvticketlock: use callee-save for lock_spinning Jeremy Fitzhardinge
-- strict thread matches above, loose matches on Subject: below --
2010-07-12 20:03 [PATCH RFC 03/12] x86/ticketlock: Use C for __ticket_spin_unlock Jeremy Fitzhardinge
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