From owner-svn-src-head@freebsd.org Fri Nov 17 02:27:06 2017 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 3E26FDF132E; Fri, 17 Nov 2017 02:27:06 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id C4A5175A8C; Fri, 17 Nov 2017 02:27:05 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id vAH2R4VC047035; Fri, 17 Nov 2017 02:27:04 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id vAH2R43C047034; Fri, 17 Nov 2017 02:27:04 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <201711170227.vAH2R43C047034@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Fri, 17 Nov 2017 02:27:04 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r325922 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 325922 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 17 Nov 2017 02:27:06 -0000 Author: mjg Date: Fri Nov 17 02:27:04 2017 New Revision: 325922 URL: https://svnweb.freebsd.org/changeset/base/325922 Log: sx: perform a minor cleanup of the unlock slowpath No functional changes. Modified: head/sys/kern/kern_sx.c Modified: head/sys/kern/kern_sx.c ============================================================================== --- head/sys/kern/kern_sx.c Fri Nov 17 02:26:15 2017 (r325921) +++ head/sys/kern/kern_sx.c Fri Nov 17 02:27:04 2017 (r325922) @@ -772,7 +772,7 @@ _sx_xlock_hard(struct sx *sx, uintptr_t x, uintptr_t t void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int line) { - uintptr_t x; + uintptr_t x, setx; int queue, wakeup_swapper; if (SCHEDULER_STOPPED()) @@ -801,7 +801,7 @@ _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const c CTR2(KTR_LOCK, "%s: %p contested", __func__, sx); sleepq_lock(&sx->lock_object); - x = SX_LOCK_UNLOCKED; + x = SX_READ_VALUE(sx); /* * The wake up algorithm here is quite simple and probably not @@ -812,19 +812,21 @@ _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const c * starvation for the threads sleeping on the exclusive queue by giving * them precedence and cleaning up the shared waiters bit anyway. */ - if ((sx->sx_lock & SX_LOCK_SHARED_WAITERS) != 0 && + setx = SX_LOCK_UNLOCKED; + queue = SQ_EXCLUSIVE_QUEUE; + if ((x & SX_LOCK_SHARED_WAITERS) != 0 && sleepq_sleepcnt(&sx->lock_object, SQ_SHARED_QUEUE) != 0) { queue = SQ_SHARED_QUEUE; - x |= (sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS); - } else - queue = SQ_EXCLUSIVE_QUEUE; + setx |= (x & SX_LOCK_EXCLUSIVE_WAITERS); + } + atomic_store_rel_ptr(&sx->sx_lock, setx); /* Wake up all the waiters for the specific queue. */ if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR3(KTR_LOCK, "%s: %p waking up all threads on %s queue", __func__, sx, queue == SQ_SHARED_QUEUE ? "shared" : "exclusive"); - atomic_store_rel_ptr(&sx->sx_lock, x); + wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, queue); sleepq_release(&sx->lock_object);