From owner-svn-src-all@freebsd.org Wed Jul 24 23:05:00 2019 Return-Path: Delivered-To: svn-src-all@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 44CC5BBCED; Wed, 24 Jul 2019 23:05:00 +0000 (UTC) (envelope-from markj@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 24786828DA; Wed, 24 Jul 2019 23:05:00 +0000 (UTC) (envelope-from markj@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 mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id F377A1DB45; Wed, 24 Jul 2019 23:04:59 +0000 (UTC) (envelope-from markj@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id x6ON4xf7039801; Wed, 24 Jul 2019 23:04:59 GMT (envelope-from markj@FreeBSD.org) Received: (from markj@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id x6ON4xX1039797; Wed, 24 Jul 2019 23:04:59 GMT (envelope-from markj@FreeBSD.org) Message-Id: <201907242304.x6ON4xX1039797@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: markj set sender to markj@FreeBSD.org using -f From: Mark Johnston Date: Wed, 24 Jul 2019 23:04:59 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r350310 - in head/sys: kern sys X-SVN-Group: head X-SVN-Commit-Author: markj X-SVN-Commit-Paths: in head/sys: kern sys X-SVN-Commit-Revision: 350310 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 24786828DA X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-2.95 / 15.00]; local_wl_from(0.00)[FreeBSD.org]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; NEURAL_HAM_SHORT(-0.95)[-0.947,0]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; ASN(0.00)[asn:11403, ipnet:2610:1c1:1::/48, country:US] X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Jul 2019 23:05:00 -0000 Author: markj Date: Wed Jul 24 23:04:59 2019 New Revision: 350310 URL: https://svnweb.freebsd.org/changeset/base/350310 Log: Fix the turnstile_lock() KPI. turnstile_{lock,unlock}() were added for use in epoch. turnstile_lock() returned NULL to indicate that the calling thread had lost a race and the turnstile was no longer associated with the given lock, or the lock owner. However, reader-writer locks may not have a designated owner, in which case turnstile_lock() would return NULL and epoch_block_handler_preempt() would leak spinlocks as a result. Apply a minimal fix: return the lock owner as a separate return value. Reviewed by: kib MFC after: 3 days Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D21048 Modified: head/sys/kern/subr_epoch.c head/sys/kern/subr_turnstile.c head/sys/sys/turnstile.h Modified: head/sys/kern/subr_epoch.c ============================================================================== --- head/sys/kern/subr_epoch.c Wed Jul 24 23:04:26 2019 (r350309) +++ head/sys/kern/subr_epoch.c Wed Jul 24 23:04:59 2019 (r350310) @@ -438,26 +438,20 @@ epoch_block_handler_preempt(struct ck_epoch *global __ */ critical_enter(); thread_unlock(td); - owner = turnstile_lock(ts, &lock); - /* - * The owner pointer indicates that the lock succeeded. - * Only in case we hold the lock and the turnstile we - * locked is still the one that curwaittd is blocked on - * can we continue. Otherwise the turnstile pointer has - * been changed out from underneath us, as in the case - * where the lock holder has signalled curwaittd, - * and we need to continue. - */ - if (owner != NULL && ts == curwaittd->td_blocked) { - MPASS(TD_IS_INHIBITED(curwaittd) && - TD_ON_LOCK(curwaittd)); - critical_exit(); - turnstile_wait(ts, owner, curwaittd->td_tsqueue); - counter_u64_add(turnstile_count, 1); - thread_lock(td); - return; - } else if (owner != NULL) + + if (turnstile_lock(ts, &lock, &owner)) { + if (ts == curwaittd->td_blocked) { + MPASS(TD_IS_INHIBITED(curwaittd) && + TD_ON_LOCK(curwaittd)); + critical_exit(); + turnstile_wait(ts, owner, + curwaittd->td_tsqueue); + counter_u64_add(turnstile_count, 1); + thread_lock(td); + return; + } turnstile_unlock(ts, lock); + } thread_lock(td); critical_exit(); KASSERT(td->td_locks == locksheld, Modified: head/sys/kern/subr_turnstile.c ============================================================================== --- head/sys/kern/subr_turnstile.c Wed Jul 24 23:04:26 2019 (r350309) +++ head/sys/kern/subr_turnstile.c Wed Jul 24 23:04:59 2019 (r350310) @@ -566,24 +566,26 @@ turnstile_trywait(struct lock_object *lock) return (ts); } -struct thread * -turnstile_lock(struct turnstile *ts, struct lock_object **lockp) +bool +turnstile_lock(struct turnstile *ts, struct lock_object **lockp, + struct thread **tdp) { struct turnstile_chain *tc; struct lock_object *lock; if ((lock = ts->ts_lockobj) == NULL) - return (NULL); + return (false); tc = TC_LOOKUP(lock); mtx_lock_spin(&tc->tc_lock); mtx_lock_spin(&ts->ts_lock); if (__predict_false(lock != ts->ts_lockobj)) { mtx_unlock_spin(&tc->tc_lock); mtx_unlock_spin(&ts->ts_lock); - return (NULL); + return (false); } *lockp = lock; - return (ts->ts_owner); + *tdp = ts->ts_owner; + return (true); } void Modified: head/sys/sys/turnstile.h ============================================================================== --- head/sys/sys/turnstile.h Wed Jul 24 23:04:26 2019 (r350309) +++ head/sys/sys/turnstile.h Wed Jul 24 23:04:59 2019 (r350310) @@ -99,7 +99,8 @@ int turnstile_signal(struct turnstile *, int); struct turnstile *turnstile_trywait(struct lock_object *); void turnstile_unpend(struct turnstile *); void turnstile_wait(struct turnstile *, struct thread *, int); -struct thread *turnstile_lock(struct turnstile *, struct lock_object **); +bool turnstile_lock(struct turnstile *, struct lock_object **, + struct thread **); void turnstile_unlock(struct turnstile *, struct lock_object *); void turnstile_assert(struct turnstile *); #endif /* _KERNEL */