From owner-svn-src-head@freebsd.org Thu Oct 5 13:01:19 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 B10F7E382F5; Thu, 5 Oct 2017 13:01:19 +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 7DCBC708C5; Thu, 5 Oct 2017 13:01:19 +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 v95D1Ixs056297; Thu, 5 Oct 2017 13:01:18 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id v95D1Iki056295; Thu, 5 Oct 2017 13:01:18 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <201710051301.v95D1Iki056295@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Thu, 5 Oct 2017 13:01:18 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r324314 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 324314 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: 2.1.23 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: Thu, 05 Oct 2017 13:01:19 -0000 Author: mjg Date: Thu Oct 5 13:01:18 2017 New Revision: 324314 URL: https://svnweb.freebsd.org/changeset/base/324314 Log: locks: partially tidy up waiting on readers spin first instant of instantly re-readoing and don't re-read after spinning is finished - the state is already known. Note the code is subject to significant changes later. MFC after: 1 week Modified: head/sys/kern/kern_rwlock.c head/sys/kern/kern_sx.c Modified: head/sys/kern/kern_rwlock.c ============================================================================== --- head/sys/kern/kern_rwlock.c Thu Oct 5 12:50:03 2017 (r324313) +++ head/sys/kern/kern_rwlock.c Thu Oct 5 13:01:18 2017 (r324314) @@ -489,12 +489,11 @@ __rw_rlock_hard(volatile uintptr_t *c, struct thread * "spinning", "lockname:\"%s\"", rw->lock_object.lo_name); for (i = 0; i < rowner_loops; i++) { + cpu_spinwait(); v = RW_READ_VALUE(rw); if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(td, v)) break; - cpu_spinwait(); } - v = RW_READ_VALUE(rw); #ifdef KDTRACE_HOOKS lda.spin_cnt += rowner_loops - i; #endif @@ -930,13 +929,13 @@ __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v, ui "spinning", "lockname:\"%s\"", rw->lock_object.lo_name); for (i = 0; i < rowner_loops; i++) { - if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0) - break; cpu_spinwait(); + v = RW_READ_VALUE(rw); + if ((v & RW_LOCK_WRITE_SPINNER) == 0) + break; } KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), "running"); - v = RW_READ_VALUE(rw); #ifdef KDTRACE_HOOKS lda.spin_cnt += rowner_loops - i; #endif Modified: head/sys/kern/kern_sx.c ============================================================================== --- head/sys/kern/kern_sx.c Thu Oct 5 12:50:03 2017 (r324313) +++ head/sys/kern/kern_sx.c Thu Oct 5 13:01:18 2017 (r324314) @@ -605,18 +605,17 @@ _sx_xlock_hard(struct sx *sx, uintptr_t x, uintptr_t t CTR4(KTR_LOCK, "%s: shared spinning on %p with %u and %u", __func__, sx, spintries, i); - x = sx->sx_lock; + cpu_spinwait(); + x = SX_READ_VALUE(sx); if ((x & SX_LOCK_SHARED) == 0 || SX_SHARERS(x) == 0) break; - cpu_spinwait(); + } #ifdef KDTRACE_HOOKS - lda.spin_cnt++; + lda.spin_cnt += i; #endif - } KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), "running"); - x = SX_READ_VALUE(sx); if (i != asx_loops) continue; }