Import the existing rwlock implementation for architectures that cannot

use  the futex(2)-based one due to missing atomic primitives.

1 files changed, 260 insertions, 0 deletions

diff --git a/lib/librthread/rthread_rwlock_compat.c b/lib/librthread/rthread_rwlock_compat.c
new file mode 100644
index 00000000000..f9dc6f858b2
--- /dev/null
+++ b/lib/librthread/rthread_rwlock_compat.c
@@ -0,0 +1,260 @@
+/*	$OpenBSD: rthread_rwlock_compat.c,v 1.1 2019/02/13 13:15:39 mpi Exp $ */
+/*
+ * Copyright (c) 2004,2005 Ted Unangst <tedu@openbsd.org>
+ * Copyright (c) 2012 Philip Guenther <guenther@openbsd.org>
+ * All Rights Reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * rwlocks
+ */
+
+#include <assert.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include <pthread.h>
+
+#include "rthread.h"
+
+static _atomic_lock_t rwlock_init_lock = _SPINLOCK_UNLOCKED;
+
+int
+pthread_rwlock_init(pthread_rwlock_t *lockp,
+    const pthread_rwlockattr_t *attrp __unused)
+{
+	pthread_rwlock_t lock;
+
+	lock = calloc(1, sizeof(*lock));
+	if (!lock)
+		return (errno);
+	lock->lock = _SPINLOCK_UNLOCKED;
+	TAILQ_INIT(&lock->writers);
+
+	*lockp = lock;
+
+	return (0);
+}
+DEF_STD(pthread_rwlock_init);
+
+int
+pthread_rwlock_destroy(pthread_rwlock_t *lockp)
+{
+	pthread_rwlock_t lock;
+
+	assert(lockp);
+	lock = *lockp;
+	if (lock) {
+		if (lock->readers || !TAILQ_EMPTY(&lock->writers)) {
+#define MSG "pthread_rwlock_destroy on rwlock with waiters!\n"
+			write(2, MSG, sizeof(MSG) - 1);
+#undef MSG
+			return (EBUSY);
+		}
+		free(lock);
+	}
+	*lockp = NULL;
+
+	return (0);
+}
+
+static int
+_rthread_rwlock_ensure_init(pthread_rwlock_t *lockp)
+{
+	int ret = 0;
+
+	/*
+	 * If the rwlock is statically initialized, perform the dynamic
+	 * initialization.
+	 */
+	if (*lockp == NULL)
+	{
+		_spinlock(&rwlock_init_lock);
+		if (*lockp == NULL)
+			ret = pthread_rwlock_init(lockp, NULL);
+		_spinunlock(&rwlock_init_lock);
+	}
+	return (ret);
+}
+
+
+static int
+_rthread_rwlock_rdlock(pthread_rwlock_t *lockp, const struct timespec *abstime,
+    int try)
+{
+	pthread_rwlock_t lock;
+	pthread_t thread = pthread_self();
+	int error;
+
+	if ((error = _rthread_rwlock_ensure_init(lockp)))
+		return (error);
+
+	lock = *lockp;
+	_rthread_debug(5, "%p: rwlock_rdlock %p\n", (void *)thread,
+	    (void *)lock);
+	_spinlock(&lock->lock);
+
+	/* writers have precedence */
+	if (lock->owner == NULL && TAILQ_EMPTY(&lock->writers))
+		lock->readers++;
+	else if (try)
+		error = EBUSY;
+	else if (lock->owner == thread)
+		error = EDEADLK;
+	else {
+		do {
+			if (__thrsleep(lock, CLOCK_REALTIME, abstime,
+			    &lock->lock, NULL) == EWOULDBLOCK)
+				return (ETIMEDOUT);
+			_spinlock(&lock->lock);
+		} while (lock->owner != NULL || !TAILQ_EMPTY(&lock->writers));
+		lock->readers++;
+	}
+	_spinunlock(&lock->lock);
+
+	return (error);
+}
+
+int
+pthread_rwlock_rdlock(pthread_rwlock_t *lockp)
+{
+	return (_rthread_rwlock_rdlock(lockp, NULL, 0));
+}
+
+int
+pthread_rwlock_tryrdlock(pthread_rwlock_t *lockp)
+{
+	return (_rthread_rwlock_rdlock(lockp, NULL, 1));
+}
+
+int
+pthread_rwlock_timedrdlock(pthread_rwlock_t *lockp,
+    const struct timespec *abstime)
+{
+	if (abstime == NULL || abstime->tv_nsec < 0 ||
+	    abstime->tv_nsec >= 1000000000)
+		return (EINVAL);
+	return (_rthread_rwlock_rdlock(lockp, abstime, 0));
+}
+
+
+static int
+_rthread_rwlock_wrlock(pthread_rwlock_t *lockp, const struct timespec *abstime,
+    int try)
+{
+	pthread_rwlock_t lock;
+	pthread_t thread = pthread_self();
+	int error;
+
+	if ((error = _rthread_rwlock_ensure_init(lockp)))
+		return (error);
+
+	lock = *lockp;
+
+	_rthread_debug(5, "%p: rwlock_timedwrlock %p\n", (void *)thread,
+	    (void *)lock);
+	_spinlock(&lock->lock);
+	if (lock->readers == 0 && lock->owner == NULL)
+		lock->owner = thread;
+	else if (try)
+		error = EBUSY;
+	else if (lock->owner == thread)
+		error = EDEADLK;
+	else {
+		int do_wait;
+
+		/* gotta block */
+		TAILQ_INSERT_TAIL(&lock->writers, thread, waiting);
+		do {
+			do_wait = __thrsleep(thread, CLOCK_REALTIME, abstime,
+			    &lock->lock, NULL) != EWOULDBLOCK;
+			_spinlock(&lock->lock);
+		} while (lock->owner != thread && do_wait);
+
+		if (lock->owner != thread) {
+			/* timed out, sigh */
+			TAILQ_REMOVE(&lock->writers, thread, waiting);
+			error = ETIMEDOUT;
+		}
+	}
+	_spinunlock(&lock->lock);
+
+	return (error);
+}
+
+int
+pthread_rwlock_wrlock(pthread_rwlock_t *lockp)
+{
+	return (_rthread_rwlock_wrlock(lockp, NULL, 0));
+}
+
+int
+pthread_rwlock_trywrlock(pthread_rwlock_t *lockp)
+{
+	return (_rthread_rwlock_wrlock(lockp, NULL, 1));
+}
+
+int
+pthread_rwlock_timedwrlock(pthread_rwlock_t *lockp,
+    const struct timespec *abstime)
+{
+	if (abstime == NULL || abstime->tv_nsec < 0 ||
+	    abstime->tv_nsec >= 1000000000)
+		return (EINVAL);
+	return (_rthread_rwlock_wrlock(lockp, abstime, 0));
+}
+
+
+int
+pthread_rwlock_unlock(pthread_rwlock_t *lockp)
+{
+	pthread_rwlock_t lock;
+	pthread_t thread = pthread_self();
+	pthread_t next;
+	int was_writer;
+
+	lock = *lockp;
+
+	_rthread_debug(5, "%p: rwlock_unlock %p\n", (void *)thread,
+	    (void *)lock);
+	_spinlock(&lock->lock);
+	if (lock->owner != NULL) {
+		assert(lock->owner == thread);
+		was_writer = 1;
+	} else {
+		assert(lock->readers > 0);
+		lock->readers--;
+		if (lock->readers > 0)
+			goto out;
+		was_writer = 0;
+	}
+
+	lock->owner = next = TAILQ_FIRST(&lock->writers);
+	if (next != NULL) {
+		/* dequeue and wake first writer */
+		TAILQ_REMOVE(&lock->writers, next, waiting);
+		_spinunlock(&lock->lock);
+		__thrwakeup(next, 1);
+		return (0);
+	}
+
+	/* could there have been blocked readers?  wake them all */
+	if (was_writer)
+		__thrwakeup(lock, 0);
+out:
+	_spinunlock(&lock->lock);
+
+	return (0);
+}