Date: Sat, 27 Jul 2019 16:11:04 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r350373 - in stable/12/sys: kern sys Message-ID: <201907271611.x6RGB4cJ032303@repo.freebsd.org>
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Author: markj Date: Sat Jul 27 16:11:04 2019 New Revision: 350373 URL: https://svnweb.freebsd.org/changeset/base/350373 Log: MFC r350310: Fix the turnstile_lock() KPI. Modified: stable/12/sys/kern/subr_epoch.c stable/12/sys/kern/subr_turnstile.c stable/12/sys/sys/turnstile.h Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/kern/subr_epoch.c ============================================================================== --- stable/12/sys/kern/subr_epoch.c Sat Jul 27 15:04:10 2019 (r350372) +++ stable/12/sys/kern/subr_epoch.c Sat Jul 27 16:11:04 2019 (r350373) @@ -440,26 +440,20 @@ 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: stable/12/sys/kern/subr_turnstile.c ============================================================================== --- stable/12/sys/kern/subr_turnstile.c Sat Jul 27 15:04:10 2019 (r350372) +++ stable/12/sys/kern/subr_turnstile.c Sat Jul 27 16:11:04 2019 (r350373) @@ -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: stable/12/sys/sys/turnstile.h ============================================================================== --- stable/12/sys/sys/turnstile.h Sat Jul 27 15:04:10 2019 (r350372) +++ stable/12/sys/sys/turnstile.h Sat Jul 27 16:11:04 2019 (r350373) @@ -100,7 +100,8 @@ 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 */
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