Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758045AbZGCMqr (ORCPT ); Fri, 3 Jul 2009 08:46:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757856AbZGCMpi (ORCPT ); Fri, 3 Jul 2009 08:45:38 -0400 Received: from hera.kernel.org ([140.211.167.34]:59950 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757730AbZGCMpe (ORCPT ); Fri, 3 Jul 2009 08:45:34 -0400 Date: Fri, 3 Jul 2009 12:44:18 GMT From: tip-bot for Eric Dumazet To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, acme@redhat.com, paulus@samba.org, hpa@zytor.com, mingo@redhat.com, eric.dumazet@gmail.com, a.p.zijlstra@chello.nl, torvalds@linux-foundation.org, efault@gmx.de, arnd@arndb.de, dhowells@redhat.com, fweisbec@gmail.com, akpm@linux-foundation.org, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, paulus@samba.org, acme@redhat.com, linux-kernel@vger.kernel.org, eric.dumazet@gmail.com, torvalds@linux-foundation.org, a.p.zijlstra@chello.nl, efault@gmx.de, arnd@arndb.de, fweisbec@gmail.com, dhowells@redhat.com, akpm@linux-foundation.org, tglx@linutronix.de, mingo@elte.hu In-Reply-To: References: Subject: [tip:perfcounters/urgent] x86: atomic64: Improve atomic64_read() Message-ID: Git-Commit-ID: 9103cab145a93cef13378632b332a824758a2f6f X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Fri, 03 Jul 2009 12:44:19 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2146 Lines: 68 Commit-ID: 9103cab145a93cef13378632b332a824758a2f6f Gitweb: http://git.kernel.org/tip/9103cab145a93cef13378632b332a824758a2f6f Author: Eric Dumazet AuthorDate: Fri, 3 Jul 2009 13:23:02 +0200 Committer: Ingo Molnar CommitDate: Fri, 3 Jul 2009 13:26:48 +0200 x86: atomic64: Improve atomic64_read() Optimize atomic64_read() as a special open-coded cmpxchg8b variant. This generates nicer code: arch/x86/lib/atomic64_32.o: text data bss dec hex filename 435 0 0 435 1b3 atomic64_32.o.before 431 0 0 431 1af atomic64_32.o.after md5: bd8ab95e69c93518578bfaf0ea3be4d9 atomic64_32.o.before.asm 2bdfd4bd1f6b7b61b7fc127aef90ce3b atomic64_32.o.after.asm Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker Cc: David Howells Cc: Andrew Morton Cc: Arnd Bergmann LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/lib/atomic64_32.c | 12 ++++++++++-- 1 files changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c index fd28fd3..079ac8e 100644 --- a/arch/x86/lib/atomic64_32.c +++ b/arch/x86/lib/atomic64_32.c @@ -62,9 +62,17 @@ void atomic64_set(atomic64_t *ptr, u64 new_val) */ u64 atomic64_read(atomic64_t *ptr) { - u64 old = 1LL << 32; + u64 res; - return cmpxchg8b(&ptr->counter, old, old); + asm volatile( + "mov %%ebx, %%eax\n\t" + "mov %%ecx, %%edx\n\t" + LOCK_PREFIX "cmpxchg8b %1\n" + : "=A" (res) + : "m" (*ptr) + ); + + return res; } /** -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/