917c07ca1d
Let fall down in the hard path (thus handling shared waiters wakeup correctly) for the shared waiters also in the rwlock held in shared mode as well, fixing possible deadlocks. Please note that this is a special condition as we want this fix in before RC2 as we assume it is critical and so it has been handled as an instant-merge. For the STABLE_7 branch, 1 week before the MFC is assumed. Approved by: re (kib)
189 lines
5.9 KiB
C
189 lines
5.9 KiB
C
/*-
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* Copyright (c) 2005 David Xu <davidxu@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _THR_FBSD_UMTX_H_
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#define _THR_FBSD_UMTX_H_
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#include <strings.h>
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#include <sys/umtx.h>
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#define DEFAULT_UMUTEX {0,0, {0,0},{0,0,0,0}}
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int __thr_umutex_lock(struct umutex *mtx, uint32_t id) __hidden;
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int __thr_umutex_timedlock(struct umutex *mtx, uint32_t id,
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const struct timespec *timeout) __hidden;
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int __thr_umutex_unlock(struct umutex *mtx, uint32_t id) __hidden;
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int __thr_umutex_trylock(struct umutex *mtx) __hidden;
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int __thr_umutex_set_ceiling(struct umutex *mtx, uint32_t ceiling,
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uint32_t *oldceiling) __hidden;
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void _thr_umutex_init(struct umutex *mtx) __hidden;
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int _thr_umtx_wait(volatile long *mtx, long exp,
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const struct timespec *timeout) __hidden;
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int _thr_umtx_wait_uint(volatile u_int *mtx, u_int exp,
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const struct timespec *timeout, int shared) __hidden;
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int _thr_umtx_wake(volatile void *mtx, int count, int shared) __hidden;
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int _thr_ucond_wait(struct ucond *cv, struct umutex *m,
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const struct timespec *timeout, int check_unpaking) __hidden;
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void _thr_ucond_init(struct ucond *cv) __hidden;
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int _thr_ucond_signal(struct ucond *cv) __hidden;
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int _thr_ucond_broadcast(struct ucond *cv) __hidden;
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int __thr_rwlock_rdlock(struct urwlock *rwlock, int flags, struct timespec *tsp) __hidden;
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int __thr_rwlock_wrlock(struct urwlock *rwlock, struct timespec *tsp) __hidden;
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int __thr_rwlock_unlock(struct urwlock *rwlock) __hidden;
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static inline int
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_thr_umutex_trylock(struct umutex *mtx, uint32_t id)
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{
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if (atomic_cmpset_acq_32(&mtx->m_owner, UMUTEX_UNOWNED, id))
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return (0);
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if ((mtx->m_flags & UMUTEX_PRIO_PROTECT) == 0)
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return (EBUSY);
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return (__thr_umutex_trylock(mtx));
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}
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static inline int
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_thr_umutex_trylock2(struct umutex *mtx, uint32_t id)
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{
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if (atomic_cmpset_acq_32(&mtx->m_owner, UMUTEX_UNOWNED, id) != 0)
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return (0);
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if ((uint32_t)mtx->m_owner == UMUTEX_CONTESTED &&
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__predict_true((mtx->m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT)) == 0))
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if (atomic_cmpset_acq_32(&mtx->m_owner, UMUTEX_CONTESTED, id | UMUTEX_CONTESTED))
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return (0);
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return (EBUSY);
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}
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static inline int
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_thr_umutex_lock(struct umutex *mtx, uint32_t id)
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{
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if (_thr_umutex_trylock2(mtx, id) == 0)
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return (0);
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return (__thr_umutex_lock(mtx, id));
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}
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static inline int
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_thr_umutex_timedlock(struct umutex *mtx, uint32_t id,
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const struct timespec *timeout)
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{
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if (_thr_umutex_trylock2(mtx, id) == 0)
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return (0);
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return (__thr_umutex_timedlock(mtx, id, timeout));
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}
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static inline int
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_thr_umutex_unlock(struct umutex *mtx, uint32_t id)
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{
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if (atomic_cmpset_rel_32(&mtx->m_owner, id, UMUTEX_UNOWNED))
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return (0);
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return (__thr_umutex_unlock(mtx, id));
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}
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static inline int
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_thr_rwlock_tryrdlock(struct urwlock *rwlock, int flags)
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{
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int32_t state;
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int32_t wrflags;
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if (flags & URWLOCK_PREFER_READER || rwlock->rw_flags & URWLOCK_PREFER_READER)
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wrflags = URWLOCK_WRITE_OWNER;
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else
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wrflags = URWLOCK_WRITE_OWNER | URWLOCK_WRITE_WAITERS;
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state = rwlock->rw_state;
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while (!(state & wrflags)) {
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if (__predict_false(URWLOCK_READER_COUNT(state) == URWLOCK_MAX_READERS))
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return (EAGAIN);
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if (atomic_cmpset_acq_32(&rwlock->rw_state, state, state + 1))
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return (0);
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state = rwlock->rw_state;
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}
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return (EBUSY);
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}
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static inline int
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_thr_rwlock_trywrlock(struct urwlock *rwlock)
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{
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int32_t state;
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state = rwlock->rw_state;
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while (!(state & URWLOCK_WRITE_OWNER) && URWLOCK_READER_COUNT(state) == 0) {
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if (atomic_cmpset_acq_32(&rwlock->rw_state, state, state | URWLOCK_WRITE_OWNER))
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return (0);
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state = rwlock->rw_state;
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}
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return (EBUSY);
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}
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static inline int
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_thr_rwlock_rdlock(struct urwlock *rwlock, int flags, struct timespec *tsp)
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{
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if (_thr_rwlock_tryrdlock(rwlock, flags) == 0)
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return (0);
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return (__thr_rwlock_rdlock(rwlock, flags, tsp));
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}
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static inline int
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_thr_rwlock_wrlock(struct urwlock *rwlock, struct timespec *tsp)
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{
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if (_thr_rwlock_trywrlock(rwlock) == 0)
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return (0);
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return (__thr_rwlock_wrlock(rwlock, tsp));
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}
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static inline int
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_thr_rwlock_unlock(struct urwlock *rwlock)
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{
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int32_t state;
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state = rwlock->rw_state;
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if (state & URWLOCK_WRITE_OWNER) {
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if (atomic_cmpset_rel_32(&rwlock->rw_state, URWLOCK_WRITE_OWNER, 0))
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return (0);
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} else {
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for (;;) {
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if (__predict_false(URWLOCK_READER_COUNT(state) == 0))
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return (EPERM);
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if (!((state & (URWLOCK_WRITE_WAITERS |
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URWLOCK_READ_WAITERS)) &&
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URWLOCK_READER_COUNT(state) == 1)) {
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if (atomic_cmpset_rel_32(&rwlock->rw_state,
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state, state-1))
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return (0);
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state = rwlock->rw_state;
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} else {
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break;
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}
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}
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}
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return (__thr_rwlock_unlock(rwlock));
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}
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#endif
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