diff -prU2 Modules/signalmodule.c Modules/signalmodule.c
--- Modules/signalmodule.c
+++ Modules/signalmodule.c
@@ -170,14 +170,18 @@ static void
 signal_handler(int sig_num)
 {
-#ifdef WITH_THREAD
-#ifdef WITH_PTH
+    int save_errno = errno;
+
+#if defined(WITH_THREAD) && defined(WITH_PTH)
     if (PyThread_get_thread_ident() != main_thread) {
         pth_raise(*(pth_t *) main_thread, sig_num);
-        return;
     }
+    else
 #endif
+    {
+#ifdef WITH_THREAD
     /* See NOTES section above */
-    if (getpid() == main_pid) {
+    if (getpid() == main_pid)
 #endif
+    {
         Handlers[sig_num].tripped = 1;
         /* Set is_tripped after setting .tripped, as it gets
@@ -186,18 +190,15 @@ signal_handler(int sig_num)
         Py_AddPendingCall(checksignals_witharg, NULL);
         if (wakeup_fd != -1)
-            write(wakeup_fd, "\0", 1);
-#ifdef WITH_THREAD
+            while (write(wakeup_fd, "", 1) < 0 && errno == EINTR) ;
     }
-#endif
+
+#ifndef HAVE_SIGACTION
 #ifdef SIGCHLD
-    if (sig_num == SIGCHLD) {
         /* To avoid infinite recursion, this signal remains
            reset until explicit re-instated.
            Don't clear the 'func' field as it is our pointer
            to the Python handler... */
-        return;
-    }
+    if (sig_num != SIGCHLD)
 #endif
-#ifndef HAVE_SIGACTION
     /* If the handler was not set up with sigaction, reinstall it.  See
      * Python/pythonrun.c for the implementation of PyOS_setsig which
@@ -205,4 +206,7 @@ signal_handler(int sig_num)
     PyOS_setsig(sig_num, signal_handler);
 #endif
+    } /* end !WITH_PTH */
+
+    if (errno != save_errno) errno = save_errno;
 }