From b102addf9f12f314f03834b18a1114229ba65b04 Mon Sep 17 00:00:00 2001
From: Witold Filipczyk <witekfl@poczta.onet.pl>
Date: Thu, 7 Mar 2024 11:44:42 +0100
Subject: [PATCH] [fg] Try to send CONT signal only from the master instance.
 Refs #287

---
 src/osdep/signals.c     | 23 ++++++++++++-----------
 src/terminal/terminal.c |  7 +++++++
 src/terminal/terminal.h |  1 +
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/osdep/signals.c b/src/osdep/signals.c
index bb9c3aa0..8bb0d0c3 100644
--- a/src/osdep/signals.c
+++ b/src/osdep/signals.c
@@ -73,21 +73,22 @@ static void
 sig_tstp(struct terminal *term)
 {
 #ifdef SIGSTOP
-	pid_t newpid;
 	pid_t pid = getpid();
 
 	block_itrm();
 #if defined (SIGCONT) && defined(SIGTTOU)
-	newpid = fork();
-	if (!newpid) {
-		sleep(1);
-		kill(pid, SIGCONT);
-		/* Use _exit() rather than exit(), so that atexit
-		 * functions are not called, and stdio output buffers
-		 * are not flushed.  Any such things must have been
-		 * inherited from the parent process, which will take
-		 * care of them when appropriate.  */
-		_exit(0);
+	if (pid == master_pid) {
+		pid_t newpid = fork();
+		if (!newpid) {
+			sleep(1);
+			kill(pid, SIGCONT);
+			/* Use _exit() rather than exit(), so that atexit
+			 * functions are not called, and stdio output buffers
+			 * are not flushed.  Any such things must have been
+			 * inherited from the parent process, which will take
+			 * care of them when appropriate.  */
+			_exit(0);
+		}
 	}
 #endif
 	raise(SIGSTOP);
diff --git a/src/terminal/terminal.c b/src/terminal/terminal.c
index e8f68920..2a415762 100644
--- a/src/terminal/terminal.c
+++ b/src/terminal/terminal.c
@@ -54,6 +54,8 @@ INIT_LIST_OF(struct terminal, terminals);
 struct hash *temporary_files;
 static void check_if_no_terminal(void);
 
+pid_t master_pid = 0;
+
 void
 clean_temporary_files(void)
 {
@@ -188,6 +190,11 @@ init_term(int fdin, int fdout)
 	term->fdin = fdin;
 	term->fdout = fdout;
 	term->master = (term->fdout == get_output_handle());
+
+	if (term->master) {
+		master_pid = getpid();
+	}
+
 	term->blocked = -1;
 
 	get_terminal_name(name + 9);
diff --git a/src/terminal/terminal.h b/src/terminal/terminal.h
index 0c91ac31..53c62f56 100644
--- a/src/terminal/terminal.h
+++ b/src/terminal/terminal.h
@@ -14,6 +14,7 @@ struct option;
 struct terminal_screen;
 struct terminal_interlink;
 
+extern pid_t master_pid;
 
 /** The terminal type, meaningful for frames (lines) drawing. */
 enum term_mode_type {