Add a "fork" of musl as //fusl.

fusl/src/thread/pthread_mutex_unlock.c

Index: fusl/src/thread/pthread_mutex_unlock.c
diff --git a/fusl/src/thread/pthread_mutex_unlock.c b/fusl/src/thread/pthread_mutex_unlock.c
new file mode 100644
index 0000000000000000000000000000000000000000..02da92a96b0b83f44b31ee91803fd74af70ecc6f
--- /dev/null
+++ b/fusl/src/thread/pthread_mutex_unlock.c
@@ -0,0 +1,37 @@
+#include "pthread_impl.h"
+
+int __pthread_mutex_unlock(pthread_mutex_t *m)
+{
+	pthread_t self;
+	int waiters = m->_m_waiters;
+	int cont;
+	int type = m->_m_type & 15;
+	int priv = (m->_m_type & 128) ^ 128;
+
+	if (type != PTHREAD_MUTEX_NORMAL) {
+		self = __pthread_self();
+		if ((m->_m_lock&0x7fffffff) != self->tid)
+			return EPERM;
+		if ((type&3) == PTHREAD_MUTEX_RECURSIVE && m->_m_count)
+			return m->_m_count--, 0;
+		if (!priv) {
+			self->robust_list.pending = &m->_m_next;
+			__vm_lock();
+		}
+		volatile void *prev = m->_m_prev;
+		volatile void *next = m->_m_next;
+		*(volatile void *volatile *)prev = next;
+		if (next != &self->robust_list.head) *(volatile void *volatile *)
+			((char *)next - sizeof(void *)) = prev;
+	}
+	cont = a_swap(&m->_m_lock, (type & 8) ? 0x40000000 : 0);
+	if (type != PTHREAD_MUTEX_NORMAL && !priv) {
+		self->robust_list.pending = 0;
+		__vm_unlock();
+	}
+	if (waiters || cont<0)
+		__wake(&m->_m_lock, 1, priv);
+	return 0;
+}
+
+weak_alias(__pthread_mutex_unlock, pthread_mutex_unlock);