From: Philipp Stephani <phst@google.com>
Date: Tue, 19 Jan 2021 20:35:06 +0000 (+0100)
Subject: Make child signal read pipe non-blocking.
X-Git-Tag: emacs-28.0.90~4204
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=8ed97a8d543b9596166c670212265dabc44aa3d5;p=emacs.git

Make child signal read pipe non-blocking.

Otherwise Emacs might hang when trying to read the pipe twice in a
row.  This is consistent with the other file descriptors we pass to
'pselect'.

* src/process.c (child_signal_init): Make read end of pipe
non-blocking.
---

diff --git a/src/process.c b/src/process.c
index 09f87908a45..57105982c15 100644
--- a/src/process.c
+++ b/src/process.c
@@ -7179,6 +7179,8 @@ child_signal_init (void)
      exits.  */
   eassert (0 <= fds[0]);
   eassert (0 <= fds[1]);
+  if (fcntl (fds[0], F_SETFL, O_NONBLOCK) != 0)
+    emacs_perror ("fcntl");
   add_read_fd (fds[0], child_signal_read, NULL);
   fd_callback_info[fds[0]].flags &= ~KEYBOARD_FD;
   child_signal_read_fd = fds[0];