From 4cebd2ded01f733957919cea9d10a67101cb7a67 Mon Sep 17 00:00:00 2001
From: Philipp Stephani
Date: Sat, 9 Jan 2021 21:17:42 +0100
Subject: Don't unblock SIGCHLD too early.

We first need to register the received process ID so that
'handle_child_signal' checks it.  Otherwise we might never call
'waitpid' for these processes, risking deadlock.

* src/callproc.c (call_process):
* src/process.c (create_process): Don't unblock SIGCHLD before
registering the process ID to wait for.

* src/callproc.c (emacs_spawn): Accept a signal set from the caller.
---
 src/process.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

(limited to 'src/process.c')

diff --git a/src/process.c b/src/process.c
index 06d750d3368..67e930e18f1 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2059,6 +2059,7 @@ create_process (Lisp_Object process, char **new_argv, Lisp_Object current_dir)
   bool pty_flag = 0;
   char pty_name[PTY_NAME_SIZE];
   Lisp_Object lisp_pty_name = Qnil;
+  sigset_t oldset;
 
   inchannel = outchannel = -1;
 
@@ -2139,13 +2140,16 @@ create_process (Lisp_Object process, char **new_argv, Lisp_Object current_dir)
   setup_process_coding_systems (process);
   char **env = make_environment_block (current_dir);
 
+  block_input ();
+  block_child_signal (&oldset);
+
   pty_flag = p->pty_flag;
   eassert (pty_flag == ! NILP (lisp_pty_name));
 
   vfork_errno
     = emacs_spawn (&pid, forkin, forkout, forkerr, new_argv, env,
                    SSDATA (current_dir),
-                   pty_flag ? SSDATA (lisp_pty_name) : NULL);
+                   pty_flag ? SSDATA (lisp_pty_name) : NULL, &oldset);
 
   eassert ((vfork_errno == 0) == (0 < pid));
 
@@ -2153,6 +2157,10 @@ create_process (Lisp_Object process, char **new_argv, Lisp_Object current_dir)
   if (pid >= 0)
     p->alive = 1;
 
+  /* Stop blocking in the parent.  */
+  unblock_child_signal (&oldset);
+  unblock_input ();
+
   /* Environment block no longer needed.  */
   unbind_to (count, Qnil);
 
-- 
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