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-rw-r--r--lib/libthr/thread/thr_rwlock.c393
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);
+}