Handling EINTR on linux epoll in case of timeout

Adding read timeout so that test won't hang

Author: ktakashi

ext/socket/selector-epoll.c

@@ -87,8 +87,14 @@ static SgObject wait_selector(unix_context_t *ctx, int nsock,
 
   evm = SG_NEW_ATOMIC2(struct epoll_event *, n * sizeof(struct epoll_event));
   c = epoll_wait(ctx->fd, evm, n, millis);
+  /*
+    EINTR  The call was interrupted by a signal handler before either
+    (1) any of the requested events occurred or (2) the
+    timeout expired; see signal(7).
 
-  if (c < 0) {
+    So, timeout is also EINTR which we do put.
+  */
+  if (c < 0 && errno != EINTR) {
     *err = errno;
     return SG_FALSE;
   }

ext/socket/test.scm

@@ -451,6 +451,7 @@
       (lambda ()
 	(let ((s (make-client-socket "localhost" (server-service server)))
 	      (msg (string->utf8 (string-append "hello " (number->string i)))))
+	  (socket-set-read-timeout! s 100) ;; 100ms
 	  (thread-sleep! delay)
 	  (guard (e (else #t))
 	    (socket-send s msg)
@@ -477,9 +478,11 @@
   (socket-close server)
 
   (values (atomic-fixnum-load result) (atomic-fixnum-load result-to)))
+
 (let-values (((r rt) (selector-test 500)))
   (test-equal "no timeout (received)" 500 r)
   (test-equal "no timeout (timedout)" 0 rt))
+
 (let-values (((r rt) (selector-test 500 (duration:of-nanos 1))))
   ;; for some reason, some sockets don't timeout.
   (test-assert "with timeout (received)" (< r 500))