u_async: add pipe() fallback for non-Linux POSIX wakeup (FreeBSD)

lib/u_async.c

@@ -1453,7 +1453,7 @@ struct UASYNC* uasync_create(void) {
     InitializeCriticalSection(&ua->posted_lock);
 
 #else
-    // POSIX: use eventfd for reliable cross-thread wakeup
+#ifdef __linux__
     ua->wakeup_pipe[0] = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
     if (ua->wakeup_pipe[0] < 0) {
         DEBUG_ERROR(DEBUG_CATEGORY_UASYNC, "eventfd() failed: %s", strerror(errno));
@@ -1461,6 +1461,19 @@ struct UASYNC* uasync_create(void) {
         return NULL;
     }
     ua->wakeup_pipe[1] = ua->wakeup_pipe[0];
+#else
+    if (pipe(ua->wakeup_pipe) < 0) {
+        DEBUG_ERROR(DEBUG_CATEGORY_UASYNC, "pipe() failed: %s", strerror(errno));
+        u_free(ua);
+        return NULL;
+    }
+    if (fcntl(ua->wakeup_pipe[0], F_SETFL, O_NONBLOCK) < 0) {
+        DEBUG_ERROR(DEBUG_CATEGORY_UASYNC, "fcntl(wakeup_pipe[0], O_NONBLOCK) failed: %s", strerror(errno));
+    }
+    if (fcntl(ua->wakeup_pipe[1], F_SETFL, O_NONBLOCK) < 0) {
+        DEBUG_ERROR(DEBUG_CATEGORY_UASYNC, "fcntl(wakeup_pipe[1], O_NONBLOCK) failed: %s", strerror(errno));
+    }
+#endif
     ua->wakeup_initialized = 1;
 
 #if HAS_EPOLL