From fd890baa1bfa9da0d3f69051c2844fde76edb9ed Mon Sep 17 00:00:00 2001 From: kib Date: Wed, 4 Mar 2015 09:29:25 +0000 Subject: [PATCH] MFC r279282: When unlocking a contested PI pthread mutex, if the queue of waiters is empty, look up the umtx_pi and disown it if the current thread owns it. git-svn-id: svn://svn.freebsd.org/base/stable/10@279583 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f --- sys/kern/kern_umtx.c | 35 +++++++++++++++++++++++++++++++++-- 1 file changed, 33 insertions(+), 2 deletions(-) diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c index e59fe7e39..c5f90e08c 100644 --- a/sys/kern/kern_umtx.c +++ b/sys/kern/kern_umtx.c @@ -1810,6 +1810,19 @@ umtx_pi_setowner(struct umtx_pi *pi, struct thread *owner) TAILQ_INSERT_TAIL(&uq_owner->uq_pi_contested, pi, pi_link); } + +/* + * Disown a PI mutex, and remove it from the owned list. + */ +static void +umtx_pi_disown(struct umtx_pi *pi) +{ + + mtx_assert(&umtx_lock, MA_OWNED); + TAILQ_REMOVE(&pi->pi_owner->td_umtxq->uq_pi_contested, pi, pi_link); + pi->pi_owner = NULL; +} + /* * Claim ownership of a PI mutex. */ @@ -2226,8 +2239,7 @@ do_unlock_pi(struct thread *td, struct umutex *m, uint32_t flags) return (EPERM); } uq_me = curthread->td_umtxq; - pi->pi_owner = NULL; - TAILQ_REMOVE(&uq_me->uq_pi_contested, pi, pi_link); + umtx_pi_disown(pi); /* get highest priority thread which is still sleeping. */ uq_first = TAILQ_FIRST(&pi->pi_blocked); while (uq_first != NULL && @@ -2248,6 +2260,25 @@ do_unlock_pi(struct thread *td, struct umutex *m, uint32_t flags) mtx_unlock_spin(&umtx_lock); if (uq_first) umtxq_signal_thread(uq_first); + } else { + pi = umtx_pi_lookup(&key); + /* + * A umtx_pi can exist if a signal or timeout removed the + * last waiter from the umtxq, but there is still + * a thread in do_lock_pi() holding the umtx_pi. + */ + if (pi != NULL) { + /* + * The umtx_pi can be unowned, such as when a thread + * has just entered do_lock_pi(), allocated the + * umtx_pi, and unlocked the umtxq. + * If the current thread owns it, it must disown it. + */ + mtx_lock_spin(&umtx_lock); + if (pi->pi_owner == td) + umtx_pi_disown(pi); + mtx_unlock_spin(&umtx_lock); + } } umtxq_unlock(&key); -- 2.45.0