From patchwork Thu Oct 12 12:20:48 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 10001789 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 1452A60325 for ; Thu, 12 Oct 2017 12:22:15 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0538622B39 for ; Thu, 12 Oct 2017 12:22:15 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EE20127480; Thu, 12 Oct 2017 12:22:14 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 8B64E26224 for ; Thu, 12 Oct 2017 12:22:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=x1F/+A3a5YCIZ33WBG66EDQjf9WQUDTjYKDLMVHPv7o=; b=GTsnW97dC4AjP/kKN5XSE8dIVT uYvuoUloIiuoBO3jKdbe1yy1Fi1rLSvrTuJuWJoeWx5Gy7apHd37UI/DTZdSr2dI+BwKcCgTidPkR 5PNdtvnO059jITPwmpVRE443/gszP6YY8SxpB4ssx9md0lOtED0/o3ILLPN7CqP1Nv6JvRLgJmGZf ylsWzHgPMPDhhdQ29o78sDwrjWNNlp8g3S85rMUAZU9ndassMrlzlsY68jRtsuTr1v50L0IdaVLSq 5VLdPcIv6dm3Ris7+wiHQmlCgngK/RRycsYECQPHx/DA3V65Ba5Cbjdm0xBtzSPyeNcwvYE0eHSpk CVK7Dimg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1e2cV7-0001mt-3v; Thu, 12 Oct 2017 12:22:09 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1e2cUB-0000Tw-2f for linux-arm-kernel@lists.infradead.org; Thu, 12 Oct 2017 12:21:15 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A4F5B15BF; Thu, 12 Oct 2017 05:20:48 -0700 (PDT) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 769183F59E; Thu, 12 Oct 2017 05:20:48 -0700 (PDT) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 268611AE2E1C; Thu, 12 Oct 2017 13:20:52 +0100 (BST) From: Will Deacon To: linux-kernel@vger.kernel.org Subject: [PATCH v3 2/5] locking/atomic: Add atomic_cond_read_acquire Date: Thu, 12 Oct 2017 13:20:48 +0100 Message-Id: <1507810851-306-3-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1507810851-306-1-git-send-email-will.deacon@arm.com> References: <1507810851-306-1-git-send-email-will.deacon@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20171012_052111_256916_DD230622 X-CRM114-Status: GOOD ( 10.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peterz@infradead.org, boqun.feng@gmail.com, Will Deacon , Jeremy.Linton@arm.com, mingo@redhat.com, longman@redhat.com, paulmck@linux.vnet.ibm.com, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP smp_cond_load_acquire provides a way to spin on a variable with acquire semantics until some conditional expression involing the variable is satisfied. Architectures such as arm64 can potentially enter a low-power state, waking up only when the value of the variable changes, which reduces the system impact of tight polling loops. This patch makes the same interface available to users of atomic_t, atomic64_t and atomic_long_t, rather than require messy accesses to the structure internals. Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E. McKenney" Signed-off-by: Will Deacon --- include/asm-generic/atomic-long.h | 3 +++ include/linux/atomic.h | 4 ++++ 2 files changed, 7 insertions(+) diff --git a/include/asm-generic/atomic-long.h b/include/asm-generic/atomic-long.h index 288cc9e96395..f2d97b782031 100644 --- a/include/asm-generic/atomic-long.h +++ b/include/asm-generic/atomic-long.h @@ -243,4 +243,7 @@ static inline long atomic_long_add_unless(atomic_long_t *l, long a, long u) #define atomic_long_inc_not_zero(l) \ ATOMIC_LONG_PFX(_inc_not_zero)((ATOMIC_LONG_PFX(_t) *)(l)) +#define atomic_long_cond_read_acquire(v, c) \ + ATOMIC_LONG_PFX(_cond_read_acquire)((ATOMIC_LONG_PFX(_t) *)(v), (c)) + #endif /* _ASM_GENERIC_ATOMIC_LONG_H */ diff --git a/include/linux/atomic.h b/include/linux/atomic.h index 40d6bfec0e0d..0aeb2b3f4578 100644 --- a/include/linux/atomic.h +++ b/include/linux/atomic.h @@ -653,6 +653,8 @@ static inline int atomic_dec_if_positive(atomic_t *v) } #endif +#define atomic_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c)) + #ifdef CONFIG_GENERIC_ATOMIC64 #include #endif @@ -1072,6 +1074,8 @@ static inline long long atomic64_fetch_andnot_release(long long i, atomic64_t *v } #endif +#define atomic64_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c)) + #include #endif /* _LINUX_ATOMIC_H */