From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964821AbbJMPps (ORCPT ); Tue, 13 Oct 2015 11:45:48 -0400 Received: from mail-pa0-f48.google.com ([209.85.220.48]:34471 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932506AbbJMPpm (ORCPT ); Tue, 13 Oct 2015 11:45:42 -0400 Date: Tue, 13 Oct 2015 23:45:18 +0800 From: Boqun Feng To: Will Deacon Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Peter Zijlstra , Ingo Molnar , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Thomas Gleixner , "Paul E. McKenney" , Waiman Long , Davidlohr Bueso Subject: Re: [PATCH v3 6/6] powerpc: atomic: Implement cmpxchg{,64}_* and atomic{,64}_cmpxchg_* variants Message-ID: <20151013154517.GD23991@fixme-laptop.cn.ibm.com> References: <1444659246-24769-1-git-send-email-boqun.feng@gmail.com> <1444659246-24769-7-git-send-email-boqun.feng@gmail.com> <20151013132404.GI21550@arm.com> <20151013143259.GB23991@fixme-laptop.cn.ibm.com> <20151013144333.GN21550@arm.com> <20151013145830.GC23991@fixme-laptop.cn.ibm.com> <20151013150427.GP21550@arm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="mSxgbZZZvrAyzONB" Content-Disposition: inline In-Reply-To: <20151013150427.GP21550@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --mSxgbZZZvrAyzONB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Oct 13, 2015 at 04:04:27PM +0100, Will Deacon wrote: > On Tue, Oct 13, 2015 at 10:58:30PM +0800, Boqun Feng wrote: > > On Tue, Oct 13, 2015 at 03:43:33PM +0100, Will Deacon wrote: > > > Putting a barrier in the middle of that critical section is probably a > > > terrible idea, and that's why I thought you were avoiding it (hence my > >=20 > > The fact is that I haven't thought of that way to implement > > cmpxchg_release before you ask that question ;-) And I'm not going to do > > that for now and probably not in the future. > >=20 > > > original question). Perhaps just add a comment to that effect, since I > >=20 > > Are you suggesting if I put a barrier in the middle I'd better to add a > > comment, right? So if I don't do that, it's OK to let this patch as it. >=20 > No, I mean put a comment in your file to explain the reason why you > override _relaxed and _acquire, but not _release (because overriding > _release would introduce this weird barrier in the middle of the critical > section, which would likely cause the conditional store to fail). >=20 Good idea, will do that. Thank you ;-) Regards, Boqun --mSxgbZZZvrAyzONB Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAABCAAGBQJWHScKAAoJEEl56MO1B/q4qAgIAKmy85ltXjBuRcN4dwS83ch7 PNh0qkC0nWb13s2fGi6udjDQnmFyEcBJybFeh3sGMZC5alQekJafh9SqO04YmX6/ RQ2aUCqR95dWBv36tSEEOMf280YjUKaB5vYmlzH5g+7M8HxX/yMPE3m8XBOwzS1P zil3+E1mMcHKUFjnfozC5oOWQgd+Sc9OVa53LtTvcI+Nivcygm9Rl24+u7Y/LUMq 5w3gSdIKt603RyKO7a3tmfSS+Ef16jjHPzKETlG2MnIo3PqdfZxi1Lel1u2riHq6 OUEGU6b4tokLpl6Z/jZBoVXgJDxPpH9HcM3kYF9qKrOLP/07L/t0dCDpWyeTumA= =rQKs -----END PGP SIGNATURE----- --mSxgbZZZvrAyzONB--