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

fusl/src/thread/pthread_mutex_trylock.c

+#include "pthread_impl.h"
+
+int __pthread_mutex_trylock_owner(pthread_mutex_t *m)
+{
+        int old, own;
+        int type = m->_m_type & 15;
+        pthread_t self = __pthread_self();
+        int tid = self->tid;
+
+        old = m->_m_lock;
+        own = old & 0x7fffffff;
+        if (own == tid && (type&3) == PTHREAD_MUTEX_RECURSIVE) {
+                if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN;
+                m->_m_count++;
+                return 0;
+        }
+        if (own == 0x40000000) return ENOTRECOVERABLE;
+
+        if (m->_m_type & 128) {
+                if (!self->robust_list.off) {
+                        self->robust_list.off = (char*)&m->_m_lock-(char *)&m->_m_next;
+                        __syscall(SYS_set_robust_list, &self->robust_list, 3*sizeof(long));
+                }
+                if (m->_m_waiters) tid |= 0x80000000;
+                self->robust_list.pending = &m->_m_next;
+        }
+
+        if ((own && (!(own & 0x40000000) || !(type & 4)))
+            || a_cas(&m->_m_lock, old, tid) != old) {
+                self->robust_list.pending = 0;
+                return EBUSY;
+        }
+
+        volatile void *next = self->robust_list.head;
+        m->_m_next = next;
+        m->_m_prev = &self->robust_list.head;
+        if (next != &self->robust_list.head) *(volatile void *volatile *)
+                ((char *)next - sizeof(void *)) = &m->_m_next;
+        self->robust_list.head = &m->_m_next;
+        self->robust_list.pending = 0;
+
+        if (own) {
+                m->_m_count = 0;
+                m->_m_type |= 8;
+                return EOWNERDEAD;
+        }
+
+        return 0;
+}
+
+int __pthread_mutex_trylock(pthread_mutex_t *m)
+{
+        if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL)
+                return a_cas(&m->_m_lock, 0, EBUSY) & EBUSY;
+        return __pthread_mutex_trylock_owner(m);
+}
+
+weak_alias(__pthread_mutex_trylock, pthread_mutex_trylock);