Revert revision 214007, I realized that MySQL wants to resolve

a silly rwlock deadlock problem, the deadlock is caused by writer
waiters, if a thread has already locked a reader lock, and wants to
acquire another reader lock, it will be blocked by writer waiters,
but we had already fixed it years ago.

4 files changed, 2 insertions, 52 deletions

diff --git a/lib/libthr/pthread.map b/lib/libthr/pthread.map
index 4094016..5e36239 100644
--- a/lib/libthr/pthread.map
+++ b/lib/libthr/pthread.map
@@ -318,9 +318,7 @@ FBSDprivate_1.0 {
 	_pthread_rwlock_wrlock;
 	_pthread_rwlockattr_destroy;
 	_pthread_rwlockattr_getpshared;
-	_pthread_rwlockattr_getkind_np;
 	_pthread_rwlockattr_init;
-	_pthread_rwlockattr_setkind_np;
 	_pthread_rwlockattr_setpshared;
 	_pthread_self;
 	_pthread_set_name_np;
@@ -403,8 +401,6 @@ FBSD_1.1 {
 
 FBSD_1.2 {
 	openat;
-	pthread_rwlockattr_getkind_np;
-	pthread_rwlockattr_setkind_np;
 	setcontext;
 	swapcontext;
 };
diff --git a/lib/libthr/thread/thr_private.h b/lib/libthr/thread/thr_private.h
index 5d0c301..aa9feef 100644
--- a/lib/libthr/thread/thr_private.h
+++ b/lib/libthr/thread/thr_private.h
@@ -285,14 +285,11 @@ struct pthread_prio {
 
 struct pthread_rwlockattr {
 	int		pshared;
-	int		kind;
 };
 
 struct pthread_rwlock {
 	struct urwlock 	lock;
 	struct pthread	*owner;
-	int	recurse;
-	int	kind;
 };
 
 /*
diff --git a/lib/libthr/thread/thr_rwlock.c b/lib/libthr/thread/thr_rwlock.c
index 20b9b79..ebdeae7 100644
--- a/lib/libthr/thread/thr_rwlock.c
+++ b/lib/libthr/thread/thr_rwlock.c
@@ -63,19 +63,13 @@ __weak_reference(_pthread_rwlock_timedwrlock, pthread_rwlock_timedwrlock);
  */
 
 static int
-rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr)
+rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr __unused)
 {
 	pthread_rwlock_t prwlock;
 
 	prwlock = (pthread_rwlock_t)calloc(1, sizeof(struct pthread_rwlock));
 	if (prwlock == NULL)
 		return (ENOMEM);
-	if (attr != NULL)
-		prwlock->kind = (*attr)->kind;
-	else
-		prwlock->kind = PTHREAD_RWLOCK_DEFAULT_NP;
-	if (prwlock->kind == PTHREAD_RWLOCK_PREFER_READER_NP)
-		prwlock->lock.rw_flags |= URWLOCK_PREFER_READER;
 	*rwlock = prwlock;
 	return (0);
 }
@@ -118,7 +112,7 @@ init_static(struct pthread *thread, pthread_rwlock_t *rwlock)
 }
 
 int
-_pthread_rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr)
+_pthread_rwlock_init (pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr)
 {
 	*rwlock = NULL;
 	return (rwlock_init(rwlock, attr));
@@ -266,14 +260,6 @@ rwlock_wrlock_common (pthread_rwlock_t *rwlock, const struct timespec *abstime)
 
 	CHECK_AND_INIT_RWLOCK
 
-	if (__predict_false(prwlock->owner == curthread)) {
-		if (__predict_false(
-			prwlock->kind == PTHREAD_RWLOCK_PREFER_WRITER_NP)) {
-			prwlock->recurse++;
-			return (0);
-		}
-	}
-
 	/*
 	 * POSIX said the validity of the abstimeout parameter need
 	 * not be checked if the lock can be immediately acquired.
@@ -349,13 +335,6 @@ _pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
 	if (state & URWLOCK_WRITE_OWNER) {
 		if (__predict_false(prwlock->owner != curthread))
 			return (EPERM);
-		if (__predict_false(
-			prwlock->kind == PTHREAD_RWLOCK_PREFER_WRITER_NP)) {
-			if (prwlock->recurse > 0) {
-				prwlock->recurse--;
-				return (0);
-			}
-		}
 		prwlock->owner = NULL;
 	}
 
diff --git a/lib/libthr/thread/thr_rwlockattr.c b/lib/libthr/thread/thr_rwlockattr.c
index 23ea73e..73ccdc9 100644
--- a/lib/libthr/thread/thr_rwlockattr.c
+++ b/lib/libthr/thread/thr_rwlockattr.c
@@ -36,10 +36,8 @@
 
 __weak_reference(_pthread_rwlockattr_destroy, pthread_rwlockattr_destroy);
 __weak_reference(_pthread_rwlockattr_getpshared, pthread_rwlockattr_getpshared);
-__weak_reference(_pthread_rwlockattr_getkind_np, pthread_rwlockattr_getkind_np);
 __weak_reference(_pthread_rwlockattr_init, pthread_rwlockattr_init);
 __weak_reference(_pthread_rwlockattr_setpshared, pthread_rwlockattr_setpshared);
-__weak_reference(_pthread_rwlockattr_setkind_np, pthread_rwlockattr_setkind_np);
 
 int
 _pthread_rwlockattr_destroy(pthread_rwlockattr_t *rwlockattr)
@@ -83,7 +81,6 @@ _pthread_rwlockattr_init(pthread_rwlockattr_t *rwlockattr)
 		return(ENOMEM);
 
 	prwlockattr->pshared 	= PTHREAD_PROCESS_PRIVATE;
-	prwlockattr->kind	= PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP;
 	*rwlockattr		= prwlockattr;
 
 	return(0);
@@ -100,22 +97,3 @@ _pthread_rwlockattr_setpshared(pthread_rwlockattr_t *rwlockattr, int pshared)
 
 	return(0);
 }
-
-int
-_pthread_rwlockattr_setkind_np(pthread_rwlockattr_t *attr, int kind)
-{
-	if (kind != PTHREAD_RWLOCK_PREFER_READER_NP &&
-	    kind != PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP &&
-	    kind != PTHREAD_RWLOCK_PREFER_WRITER_NP) {
-		return (EINVAL);
-	}
-	(*attr)->kind = kind;
-	return (0);
-}
-
-int
-_pthread_rwlockattr_getkind_np(const pthread_rwlockattr_t *attr, int *kind)
-{
-	*kind = (*attr)->kind;
-	return (0);
-}