From patchwork Thu Sep 7 17:47:01 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 13376747 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F492EC8742 for ; Thu, 7 Sep 2023 17:48:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245477AbjIGRsC (ORCPT ); Thu, 7 Sep 2023 13:48:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49280 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245527AbjIGRru (ORCPT ); Thu, 7 Sep 2023 13:47:50 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79D261FF3; Thu, 7 Sep 2023 10:47:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=LLFJT9lhOndsodIHfPQ9LEtDlXX6YGclPNMO2t1USgU=; b=jAKEfKshiWNUs4KA27DrmnJak0 fotEfuCnFgJxrpNUy54FTDDByW/E9sBz1SE2zakIlZJhp1hvXQ/JrczFhZlH5vBtzyTCrBEViEZ1r rD2XlLJb/lmeXQvvhgAR1iFsykO9s7L/WtUzp4faEt4pLZWRXY68YIibxqDRTv/VmZzG6Z/HQjVcK WuDOyAggJnPFYDxeVSPWQmtmGsGIvkM67ia+qMuyl1Axj3bfOOoVGq16Elsg7Un3O2gVO45V950KH Cs5NbUja00oSR1Ep8FiYLK7eeJGKRtDPUrjGr35KP12gtU4KJaIFuyWbCHsCgPd1jB3NrkeDddkYO lp9gc8kQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qeJ5v-00CUFJ-Uv; Thu, 07 Sep 2023 17:47:07 +0000 From: "Matthew Wilcox (Oracle)" To: Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long Cc: "Matthew Wilcox (Oracle)" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Chandan Babu R , "Darrick J . Wong" , linux-xfs@vger.kernel.org Subject: [PATCH 1/5] locking: Add rwsem_is_write_locked() Date: Thu, 7 Sep 2023 18:47:01 +0100 Message-Id: <20230907174705.2976191-2-willy@infradead.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20230907174705.2976191-1-willy@infradead.org> References: <20230907174705.2976191-1-willy@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org Several places want to know whether the lock is held by a writer, instead of just whether it's held. We can implement this for both normal and rt rwsems. RWSEM_WRITER_LOCKED is declared in rwsem.c and exposing it outside that file might tempt other people to use it, so just use a comment to note that's what the 1 means, and help anybody find it if they're looking to change the implementation. Signed-off-by: Matthew Wilcox (Oracle) --- include/linux/rwbase_rt.h | 5 +++++ include/linux/rwsem.h | 10 ++++++++++ 2 files changed, 15 insertions(+) diff --git a/include/linux/rwbase_rt.h b/include/linux/rwbase_rt.h index 1d264dd08625..3c25b14edc05 100644 --- a/include/linux/rwbase_rt.h +++ b/include/linux/rwbase_rt.h @@ -31,6 +31,11 @@ static __always_inline bool rw_base_is_locked(struct rwbase_rt *rwb) return atomic_read(&rwb->readers) != READER_BIAS; } +static __always_inline bool rw_base_is_write_locked(struct rwbase_rt *rwb) +{ + return atomic_read(&rwb->readers) == WRITER_BIAS; +} + static __always_inline bool rw_base_is_contended(struct rwbase_rt *rwb) { return atomic_read(&rwb->readers) > 0; diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 1dd530ce8b45..0f78b8d2e653 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -72,6 +72,11 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem) return atomic_long_read(&sem->count) != 0; } +static inline int rwsem_is_write_locked(struct rw_semaphore *sem) +{ + return atomic_long_read(&sem->count) & 1 /* RWSEM_WRITER_LOCKED */; +} + #define RWSEM_UNLOCKED_VALUE 0L #define __RWSEM_COUNT_INIT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE) @@ -157,6 +162,11 @@ static __always_inline int rwsem_is_locked(struct rw_semaphore *sem) return rw_base_is_locked(&sem->rwbase); } +static __always_inline int rwsem_is_write_locked(struct rw_semaphore *sem) +{ + return rw_base_is_write_locked(&sem->rwbase); +} + static __always_inline int rwsem_is_contended(struct rw_semaphore *sem) { return rw_base_is_contended(&sem->rwbase);