Date: Tue, 2 Nov 2010 06:58:01 +0000 (UTC) From: David Xu <davidxu@FreeBSD.org> To: src-committers@freebsd.org, svn-src-user@freebsd.org Subject: svn commit: r214659 - user/davidxu/libthr/lib/libthr/thread Message-ID: <201011020658.oA26w1Aq025063@svn.freebsd.org>
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Author: davidxu Date: Tue Nov 2 06:58:01 2010 New Revision: 214659 URL: http://svn.freebsd.org/changeset/base/214659 Log: For simple mutex, we don't use thread id as owner data, instead use some contants. This eliminates the need to link the mutex into thread's private list, saves some cycles. The m_owner is pointer of curthread, which is always duplicated in child process after fork(), so for atfork handler in child process which wants to unlock the mutex, it will success rather than return EPERM. Modified: user/davidxu/libthr/lib/libthr/thread/thr_mutex.c user/davidxu/libthr/lib/libthr/thread/thr_private.h Modified: user/davidxu/libthr/lib/libthr/thread/thr_mutex.c ============================================================================== --- user/davidxu/libthr/lib/libthr/thread/thr_mutex.c Tue Nov 2 06:47:18 2010 (r214658) +++ user/davidxu/libthr/lib/libthr/thread/thr_mutex.c Tue Nov 2 06:58:01 2010 (r214659) @@ -156,7 +156,7 @@ mutex_init(pthread_mutex_t *mutex, MUTEX_INIT_LINK(pmutex); switch(attr->m_protocol) { case PTHREAD_PRIO_NONE: - pmutex->m_lock.m_owner = UMUTEX_UNOWNED; + pmutex->m_lock.m_owner = 0; pmutex->m_lock.m_flags = 0; break; case PTHREAD_PRIO_INHERIT: @@ -314,23 +314,51 @@ _pthread_mutex_destroy(pthread_mutex_t * m = *mutex; \ } +static inline int +set_lockword(struct pthread_mutex *m) +{ + uint32_t old; + + if (atomic_cmpset_acq_32(&m->m_lockword, 0, MTX_LOCKED)) + return (0); + old = m->m_lockword; + while ((old & MTX_LOCKED) == 0) { + if (atomic_cmpset_acq_32(&m->m_lockword, old, old|MTX_LOCKED)) + return (0); + } + return (EBUSY); +} + static int mutex_trylock_common(pthread_mutex_t *mutex) { struct pthread *curthread = _get_curthread(); struct pthread_mutex *m = *mutex; - uint32_t id; int error; - id = TID(curthread); if (m->m_private) THR_CRITICAL_ENTER(curthread); - error = _thr_umutex_trylock(&m->m_lock, id); - if (__predict_true(error == 0)) { - ENQUEUE_MUTEX(curthread, m); - } else if (m->m_owner == curthread) { - error = mutex_self_trylock(m); - } /* else {} */ + if (IS_SIMPLE_MUTEX(m)) { + if (set_lockword(m) == 0) { + m->m_owner = curthread; + return (0); + } + + if (m->m_owner == curthread) + error = mutex_self_trylock(m); + else + error = EBUSY; + } else { + uint32_t id; + + id = TID(curthread); + error = _thr_umutex_trylock(&m->m_lock, id); + if (__predict_true(error == 0)) { + ENQUEUE_MUTEX(curthread, m); + } else if (m->m_owner == curthread) { + error = mutex_self_trylock(m); + } /* else {} */ + } if (error != 0 && m->m_private) THR_CRITICAL_LEAVE(curthread); return (error); @@ -353,16 +381,22 @@ mutex_lock_queued(struct pthread_mutex * { struct pthread *curthread = _get_curthread(); struct sleepqueue *sq; - uint32_t owner, tid; + uint32_t old; int error = 0; int spin; + if (m->m_owner == curthread) + return mutex_self_lock(m, abstime); + + if (__predict_false(abstime != NULL && + (abstime->tv_sec < 0 || abstime->tv_nsec < 0 || + abstime->tv_nsec >= 1000000000))) + return (EINVAL); + spin = m->m_spinloops; - tid = TID(curthread); for (;;) { if (!_thr_is_smp) goto sleep; - while (spin-- > 0) { /* * For adaptive mutexes, spin for a bit in the expectation @@ -370,10 +404,10 @@ mutex_lock_queued(struct pthread_mutex * * the lock is likely to be released quickly and it is * faster than entering the kernel */ - owner = m->m_lockword; - if ((owner & UMUTEX_TIDMASK) == 0) { - if (atomic_cmpset_acq_32(&m->m_lockword, owner, owner|tid)) { - ENQUEUE_MUTEX(curthread, m); + old = m->m_lockword; + if ((old & MTX_LOCKED) == 0) { + if (set_lockword(m) == 0) { + m->m_owner = curthread; error = 0; goto out; } @@ -387,15 +421,15 @@ sleep: if (curthread->wchan == NULL) _sleepq_add(sq, curthread); _sleepq_unlock(sq); - owner = m->m_lockword; + old = m->m_lockword; /* Set contested bit. */ - while ((owner & UMUTEX_TIDMASK) != 0 && (owner & UMUTEX_CONTESTED) == 0) { + while ((old & MTX_LOCKED) != 0 && (old & MTX_CONTESTED) == 0) { if (atomic_cmpset_acq_32(&m->m_lockword, - owner, owner|UMUTEX_CONTESTED)) + old, old|MTX_CONTESTED)) break; - owner = m->m_lockword; + old = m->m_lockword; } - if ((owner & UMUTEX_TIDMASK) != 0) { + if ((old & MTX_LOCKED) != 0) { error = _thr_sleep(curthread, abstime, CLOCK_REALTIME); if (error != EINTR) { if (curthread->wchan != NULL) { @@ -406,14 +440,12 @@ sleep: } } else error = 0; - owner = m->m_lockword; + old = m->m_lockword; } - if ((owner & UMUTEX_TIDMASK) == 0) { - if (atomic_cmpset_acq_32(&m->m_lockword, owner, owner|tid)) { - ENQUEUE_MUTEX(curthread, m); - error = 0; - break; - } + if (set_lockword(m) == 0) { + m->m_owner = curthread; + error = 0; + break; } if (error != 0) break; @@ -438,6 +470,14 @@ mutex_lock_kernel(struct pthread_mutex * uint32_t id; int error; + if (m->m_owner == curthread) + return mutex_self_lock(m, abstime); + + if (__predict_false(abstime != NULL && + (abstime->tv_sec < 0 || abstime->tv_nsec < 0 || + abstime->tv_nsec >= 1000000000))) + return (EINVAL); + id = TID(curthread); if (abstime == NULL) { error = __thr_umutex_lock(&m->m_lock, id); @@ -453,24 +493,20 @@ static inline int _mutex_lock_common(struct pthread_mutex *m, const struct timespec *abstime) { struct pthread *curthread = _get_curthread(); - int error; - if (_thr_umutex_trylock2(&m->m_lock, TID(curthread)) == 0) { - ENQUEUE_MUTEX(curthread, m); - error = 0; - } else if (m->m_owner == curthread) { - error = mutex_self_lock(m, abstime); + if (IS_SIMPLE_MUTEX(m)) { + if (set_lockword(m) == 0) { + m->m_owner = curthread; + return (0); + } + return mutex_lock_queued(m, abstime); } else { - if (__predict_false(abstime != NULL && - (abstime->tv_sec < 0 || abstime->tv_nsec < 0 || - abstime->tv_nsec >= 1000000000))) - error = EINVAL; - else if (__predict_true(IS_SIMPLE_MUTEX(m))) - error = mutex_lock_queued(m, abstime); - else - error = mutex_lock_kernel(m, abstime); + if (_thr_umutex_trylock2(&m->m_lock, TID(curthread)) == 0) { + ENQUEUE_MUTEX(curthread, m); + return (0); + } + return mutex_lock_kernel(m, abstime); } - return (error); } static inline int @@ -621,21 +657,21 @@ mutex_unlock_queued(struct pthread *curt { struct pthread *td; unsigned int *wake_addr = NULL; - uint32_t tid = TID(curthread); struct sleepqueue *sq; int32_t newval; - if (!atomic_cmpset_rel_32(&m->m_lock.m_owner, tid, UMUTEX_UNOWNED)) { + m->m_owner = NULL; + if (!atomic_cmpset_rel_32(&m->m_lock.m_owner, MTX_LOCKED, 0)) { sq = _sleepq_lock(m, MX); if ((td = _sleepq_first(sq)) != NULL) { _sleepq_remove(sq, td); if (_sleepq_empty(sq)) - newval = UMUTEX_UNOWNED; + newval = 0; else - newval = UMUTEX_CONTESTED; + newval = MTX_CONTESTED; wake_addr = WAKE_ADDR(td); } else { - newval = UMUTEX_UNOWNED; + newval = 0; wake_addr = NULL; } atomic_store_rel_32(&m->m_lockword, newval); @@ -679,11 +715,12 @@ _mutex_unlock_common(struct pthread *cur m->m_recurse--; return (0); } - DEQUEUE_MUTEX(curthread, m); if (__predict_true(IS_SIMPLE_MUTEX(m))) mutex_unlock_queued(curthread, m); - else + else { + DEQUEUE_MUTEX(curthread, m); _thr_umutex_unlock(&m->m_lock, tid); + } return (0); } Modified: user/davidxu/libthr/lib/libthr/thread/thr_private.h ============================================================================== --- user/davidxu/libthr/lib/libthr/thread/thr_private.h Tue Nov 2 06:47:18 2010 (r214658) +++ user/davidxu/libthr/lib/libthr/thread/thr_private.h Tue Nov 2 06:58:01 2010 (r214659) @@ -145,6 +145,9 @@ struct sleepqueue { #define MX 0 #define CV 1 +#define MTX_LOCKED 0x01 +#define MTX_CONTESTED 0x02 + struct pthread_mutex { /* * Lock for accesses to this structure. @@ -885,7 +888,7 @@ _sleepq_first(struct sleepqueue *sq) static inline void _mutex_set_contested(struct pthread_mutex *m) { - atomic_set_32(&m->m_lock.m_owner, UMUTEX_CONTESTED); + atomic_set_32(&m->m_lock.m_owner, MTX_CONTESTED); } __END_DECLS
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