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

fusl/src/thread/__timedwait.c

+#include <pthread.h>
+#include <time.h>
+#include <errno.h>
+#include "futex.h"
+#include "syscall.h"
+#include "pthread_impl.h"
+
+int __pthread_setcancelstate(int, int *);
+int __clock_gettime(clockid_t, struct timespec *);
+
+int __timedwait_cp(volatile int *addr, int val,
+        clockid_t clk, const struct timespec *at, int priv)
+{
+        int r;
+        struct timespec to, *top=0;
+
+        if (priv) priv = 128;
+
+        if (at) {
+                if (at->tv_nsec >= 1000000000UL) return EINVAL;
+                if (__clock_gettime(clk, &to)) return EINVAL;
+                to.tv_sec = at->tv_sec - to.tv_sec;
+                if ((to.tv_nsec = at->tv_nsec - to.tv_nsec) < 0) {
+                        to.tv_sec--;
+                        to.tv_nsec += 1000000000;
+                }
+                if (to.tv_sec < 0) return ETIMEDOUT;
+                top = &to;
+        }
+
+        r = -__syscall_cp(SYS_futex, addr, FUTEX_WAIT|priv, val, top);
+        if (r == ENOSYS) r = -__syscall_cp(SYS_futex, addr, FUTEX_WAIT, val, top);
+        if (r != EINTR && r != ETIMEDOUT && r != ECANCELED) r = 0;
+
+        return r;
+}
+
+int __timedwait(volatile int *addr, int val,
+        clockid_t clk, const struct timespec *at, int priv)
+{
+        int cs, r;
+        __pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+        r = __timedwait_cp(addr, val, clk, at, priv);
+        __pthread_setcancelstate(cs, 0);
+        return r;
+}