Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754932AbbBBDzK (ORCPT ); Sun, 1 Feb 2015 22:55:10 -0500 Received: from cnbjrel02.sonyericsson.com ([219.141.167.166]:9361 "EHLO cnbjrel02.sonyericsson.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754668AbbBBDzI convert rfc822-to-8bit (ORCPT ); Sun, 1 Feb 2015 22:55:08 -0500 From: "Wang, Yalin" To: "'arnd@arndb.de'" , "'linux-arch@vger.kernel.org'" , "'linux-kernel@vger.kernel.org'" , "'linux@arm.linux.org.uk'" , "'linux-arm-kernel@lists.infradead.org'" Date: Mon, 2 Feb 2015 11:55:03 +0800 Subject: [RFC] change non-atomic bitops method Thread-Topic: [RFC] change non-atomic bitops method Thread-Index: AdA+nAW4x5WD6aEBQYC4l6Bqc1ilTA== Message-ID: <35FD53F367049845BC99AC72306C23D1044A02027E0A@CNBJMBX05.corpusers.net> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2073 Lines: 64 This patch change non-atomic bitops, add a if() condition to test it, before set/clear the bit. so that we don't need dirty the cache line, if this bit have been set or clear. On SMP system, dirty cache line will need invalidate other processors cache line, this will have some impact on SMP systems. Signed-off-by: Yalin Wang --- include/asm-generic/bitops/non-atomic.h | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/include/asm-generic/bitops/non-atomic.h b/include/asm-generic/bitops/non-atomic.h index 697cc2b..e4ef18a 100644 --- a/include/asm-generic/bitops/non-atomic.h +++ b/include/asm-generic/bitops/non-atomic.h @@ -17,7 +17,9 @@ static inline void __set_bit(int nr, volatile unsigned long *addr) unsigned long mask = BIT_MASK(nr); unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); - *p |= mask; + if ((*p & mask) == 0) + *p |= mask; + } static inline void __clear_bit(int nr, volatile unsigned long *addr) @@ -25,7 +27,8 @@ static inline void __clear_bit(int nr, volatile unsigned long *addr) unsigned long mask = BIT_MASK(nr); unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); - *p &= ~mask; + if ((*p & mask) != 0) + *p &= ~mask; } /** @@ -60,7 +63,8 @@ static inline int __test_and_set_bit(int nr, volatile unsigned long *addr) unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); unsigned long old = *p; - *p = old | mask; + if ((old & mask) == 0) + *p = old | mask; return (old & mask) != 0; } @@ -79,7 +83,8 @@ static inline int __test_and_clear_bit(int nr, volatile unsigned long *addr) unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr); unsigned long old = *p; - *p = old & ~mask; + if ((old & mask) != 0) + *p = old & ~mask; return (old & mask) != 0; } -- 2.2.2 -- 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/