diff options
Diffstat (limited to 'lib/libthr/thread/thr_rwlock.c')
-rw-r--r-- | lib/libthr/thread/thr_rwlock.c | 393 |
1 files changed, 393 insertions, 0 deletions
diff --git a/lib/libthr/thread/thr_rwlock.c b/lib/libthr/thread/thr_rwlock.c new file mode 100644 index 000000000000..084181ba922a --- /dev/null +++ b/lib/libthr/thread/thr_rwlock.c @@ -0,0 +1,393 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause + * + * Copyright (c) 1998 Alex Nash + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <errno.h> +#include <limits.h> +#include <stdlib.h> +#include <string.h> + +#include "namespace.h" +#include <pthread.h> +#include "un-namespace.h" +#include "thr_private.h" + +_Static_assert(sizeof(struct pthread_rwlock) <= THR_PAGE_SIZE_MIN, + "pthread_rwlock is too large for off-page"); + +__weak_reference(_thr_rwlock_destroy, pthread_rwlock_destroy); +__weak_reference(_thr_rwlock_destroy, _pthread_rwlock_destroy); +__weak_reference(_thr_rwlock_init, pthread_rwlock_init); +__weak_reference(_thr_rwlock_init, _pthread_rwlock_init); +__weak_reference(_Tthr_rwlock_rdlock, pthread_rwlock_rdlock); +__weak_reference(_Tthr_rwlock_rdlock, _pthread_rwlock_rdlock); +__weak_reference(_pthread_rwlock_timedrdlock, pthread_rwlock_timedrdlock); +__weak_reference(_Tthr_rwlock_tryrdlock, pthread_rwlock_tryrdlock); +__weak_reference(_Tthr_rwlock_tryrdlock, _pthread_rwlock_tryrdlock); +__weak_reference(_Tthr_rwlock_trywrlock, pthread_rwlock_trywrlock); +__weak_reference(_Tthr_rwlock_trywrlock, _pthread_rwlock_trywrlock); +__weak_reference(_Tthr_rwlock_unlock, pthread_rwlock_unlock); +__weak_reference(_Tthr_rwlock_unlock, _pthread_rwlock_unlock); +__weak_reference(_Tthr_rwlock_wrlock, pthread_rwlock_wrlock); +__weak_reference(_Tthr_rwlock_wrlock, _pthread_rwlock_wrlock); +__weak_reference(_pthread_rwlock_timedwrlock, pthread_rwlock_timedwrlock); + +static int init_static(struct pthread *thread, pthread_rwlock_t *rwlock); +static int init_rwlock(pthread_rwlock_t *rwlock, pthread_rwlock_t *rwlock_out); + +static __always_inline int +check_and_init_rwlock(pthread_rwlock_t *rwlock, pthread_rwlock_t *rwlock_out) +{ + if (__predict_false(*rwlock == THR_PSHARED_PTR || + *rwlock <= THR_RWLOCK_DESTROYED)) + return (init_rwlock(rwlock, rwlock_out)); + *rwlock_out = *rwlock; + return (0); +} + +static int __noinline +init_rwlock(pthread_rwlock_t *rwlock, pthread_rwlock_t *rwlock_out) +{ + pthread_rwlock_t prwlock; + int ret; + + if (*rwlock == THR_PSHARED_PTR) { + prwlock = __thr_pshared_offpage(rwlock, 0); + if (prwlock == NULL) + return (EINVAL); + } else if ((prwlock = *rwlock) <= THR_RWLOCK_DESTROYED) { + if (prwlock == THR_RWLOCK_INITIALIZER) { + ret = init_static(_get_curthread(), rwlock); + if (ret != 0) + return (ret); + } else if (prwlock == THR_RWLOCK_DESTROYED) { + return (EINVAL); + } + prwlock = *rwlock; + } + *rwlock_out = prwlock; + return (0); +} + +static int +rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr) +{ + pthread_rwlock_t prwlock; + + if (attr == NULL || *attr == NULL || + (*attr)->pshared == PTHREAD_PROCESS_PRIVATE) { + prwlock = aligned_alloc(CACHE_LINE_SIZE, + roundup(sizeof(struct pthread_rwlock), CACHE_LINE_SIZE)); + if (prwlock == NULL) + return (ENOMEM); + memset(prwlock, 0, sizeof(struct pthread_rwlock)); + *rwlock = prwlock; + } else { + prwlock = __thr_pshared_offpage(rwlock, 1); + if (prwlock == NULL) + return (EFAULT); + prwlock->lock.rw_flags |= USYNC_PROCESS_SHARED; + *rwlock = THR_PSHARED_PTR; + } + return (0); +} + +int +_thr_rwlock_destroy(pthread_rwlock_t *rwlock) +{ + pthread_rwlock_t prwlock; + int ret; + + prwlock = *rwlock; + if (prwlock == THR_RWLOCK_INITIALIZER) + ret = 0; + else if (prwlock == THR_RWLOCK_DESTROYED) + ret = EINVAL; + else if (prwlock == THR_PSHARED_PTR) { + *rwlock = THR_RWLOCK_DESTROYED; + __thr_pshared_destroy(rwlock); + ret = 0; + } else { + *rwlock = THR_RWLOCK_DESTROYED; + free(prwlock); + ret = 0; + } + return (ret); +} + +static int +init_static(struct pthread *thread, pthread_rwlock_t *rwlock) +{ + int ret; + + THR_LOCK_ACQUIRE(thread, &_rwlock_static_lock); + + if (*rwlock == THR_RWLOCK_INITIALIZER) + ret = rwlock_init(rwlock, NULL); + else + ret = 0; + + THR_LOCK_RELEASE(thread, &_rwlock_static_lock); + + return (ret); +} + +int +_thr_rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr) +{ + + _thr_check_init(); + *rwlock = NULL; + return (rwlock_init(rwlock, attr)); +} + +static int +rwlock_rdlock_common(pthread_rwlock_t *rwlock, const struct timespec *abstime) +{ + struct pthread *curthread = _get_curthread(); + pthread_rwlock_t prwlock; + int flags; + int ret; + + ret = check_and_init_rwlock(rwlock, &prwlock); + if (ret != 0) + return (ret); + + if (curthread->rdlock_count) { + /* + * To avoid having to track all the rdlocks held by + * a thread or all of the threads that hold a rdlock, + * we keep a simple count of all the rdlocks held by + * a thread. If a thread holds any rdlocks it is + * possible that it is attempting to take a recursive + * rdlock. If there are blocked writers and precedence + * is given to them, then that would result in the thread + * deadlocking. So allowing a thread to take the rdlock + * when it already has one or more rdlocks avoids the + * deadlock. I hope the reader can follow that logic ;-) + */ + flags = URWLOCK_PREFER_READER; + } else { + flags = 0; + } + + /* + * POSIX said the validity of the abstimeout parameter need + * not be checked if the lock can be immediately acquired. + */ + ret = _thr_rwlock_tryrdlock(&prwlock->lock, flags); + if (ret == 0) { + curthread->rdlock_count++; + return (ret); + } + + if (__predict_false(abstime && + (abstime->tv_nsec >= 1000000000 || abstime->tv_nsec < 0))) + return (EINVAL); + + for (;;) { + /* goto kernel and lock it */ + ret = __thr_rwlock_rdlock(&prwlock->lock, flags, abstime); + if (ret != EINTR) + break; + + /* if interrupted, try to lock it in userland again. */ + if (_thr_rwlock_tryrdlock(&prwlock->lock, flags) == 0) { + ret = 0; + break; + } + } + if (ret == 0) + curthread->rdlock_count++; + return (ret); +} + +int +_Tthr_rwlock_rdlock(pthread_rwlock_t *rwlock) +{ + _thr_check_init(); + return (rwlock_rdlock_common(rwlock, NULL)); +} + +int +_pthread_rwlock_timedrdlock(pthread_rwlock_t * __restrict rwlock, + const struct timespec * __restrict abstime) +{ + _thr_check_init(); + return (rwlock_rdlock_common(rwlock, abstime)); +} + +int +_Tthr_rwlock_tryrdlock(pthread_rwlock_t *rwlock) +{ + struct pthread *curthread; + pthread_rwlock_t prwlock; + int flags; + int ret; + + _thr_check_init(); + ret = check_and_init_rwlock(rwlock, &prwlock); + if (ret != 0) + return (ret); + + curthread = _get_curthread(); + if (curthread->rdlock_count) { + /* + * To avoid having to track all the rdlocks held by + * a thread or all of the threads that hold a rdlock, + * we keep a simple count of all the rdlocks held by + * a thread. If a thread holds any rdlocks it is + * possible that it is attempting to take a recursive + * rdlock. If there are blocked writers and precedence + * is given to them, then that would result in the thread + * deadlocking. So allowing a thread to take the rdlock + * when it already has one or more rdlocks avoids the + * deadlock. I hope the reader can follow that logic ;-) + */ + flags = URWLOCK_PREFER_READER; + } else { + flags = 0; + } + + ret = _thr_rwlock_tryrdlock(&prwlock->lock, flags); + if (ret == 0) + curthread->rdlock_count++; + return (ret); +} + +int +_Tthr_rwlock_trywrlock(pthread_rwlock_t *rwlock) +{ + struct pthread *curthread; + pthread_rwlock_t prwlock; + int ret; + + _thr_check_init(); + ret = check_and_init_rwlock(rwlock, &prwlock); + if (ret != 0) + return (ret); + + curthread = _get_curthread(); + ret = _thr_rwlock_trywrlock(&prwlock->lock); + if (ret == 0) + prwlock->owner = TID(curthread); + return (ret); +} + +static int +rwlock_wrlock_common(pthread_rwlock_t *rwlock, const struct timespec *abstime) +{ + struct pthread *curthread = _get_curthread(); + pthread_rwlock_t prwlock; + int ret; + + ret = check_and_init_rwlock(rwlock, &prwlock); + if (ret != 0) + return (ret); + + /* + * POSIX said the validity of the abstimeout parameter need + * not be checked if the lock can be immediately acquired. + */ + ret = _thr_rwlock_trywrlock(&prwlock->lock); + if (ret == 0) { + prwlock->owner = TID(curthread); + return (ret); + } + + if (__predict_false(abstime && + (abstime->tv_nsec >= 1000000000 || abstime->tv_nsec < 0))) + return (EINVAL); + + for (;;) { + /* goto kernel and lock it */ + ret = __thr_rwlock_wrlock(&prwlock->lock, abstime); + if (ret == 0) { + prwlock->owner = TID(curthread); + break; + } + + if (ret != EINTR) + break; + + /* if interrupted, try to lock it in userland again. */ + if (_thr_rwlock_trywrlock(&prwlock->lock) == 0) { + ret = 0; + prwlock->owner = TID(curthread); + break; + } + } + return (ret); +} + +int +_Tthr_rwlock_wrlock(pthread_rwlock_t *rwlock) +{ + _thr_check_init(); + return (rwlock_wrlock_common(rwlock, NULL)); +} + +int +_pthread_rwlock_timedwrlock(pthread_rwlock_t * __restrict rwlock, + const struct timespec * __restrict abstime) +{ + _thr_check_init(); + return (rwlock_wrlock_common(rwlock, abstime)); +} + +int +_Tthr_rwlock_unlock(pthread_rwlock_t *rwlock) +{ + struct pthread *curthread = _get_curthread(); + pthread_rwlock_t prwlock; + int ret; + int32_t state; + + if (*rwlock == THR_PSHARED_PTR) { + prwlock = __thr_pshared_offpage(rwlock, 0); + if (prwlock == NULL) + return (EINVAL); + } else { + prwlock = *rwlock; + } + + if (__predict_false(prwlock <= THR_RWLOCK_DESTROYED)) + return (EINVAL); + + state = prwlock->lock.rw_state; + if (state & URWLOCK_WRITE_OWNER) { + if (__predict_false(prwlock->owner != TID(curthread))) + return (EPERM); + prwlock->owner = 0; + } + + ret = _thr_rwlock_unlock(&prwlock->lock); + if (ret == 0 && (state & URWLOCK_WRITE_OWNER) == 0) + curthread->rdlock_count--; + + return (ret); +} |