From 1307af30ec3e2bfaeeca45a63fbc944791662226 Mon Sep 17 00:00:00 2001
From: Jonas Faklkevik <jonas.falkevik@gmail.com>
Date: Mon, 2 May 2011 20:10:05 +0200
Subject: Teach run_erl RUN_ERL_DISABLE_FLOWCNTRL for disabling flow control
Flow control can cause unwanted behaviour of the beam process,
if accidentally hit Ctrl-S (instead of Ctrl-D to detach) the
entire beam may be blocked.
Fix this problem by making it possible to turn off flow
control by setting the environment variable RUN_ERL_DISABLE_FLOWCNTRL.
---
erts/doc/src/run_erl.xml | 8 ++++++++
erts/etc/unix/run_erl.c | 21 +++++++++++++++++++--
2 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/erts/doc/src/run_erl.xml b/erts/doc/src/run_erl.xml
index 7bf7f559c5..da08859c7b 100644
--- a/erts/doc/src/run_erl.xml
+++ b/erts/doc/src/run_erl.xml
@@ -144,6 +144,14 @@
<item>The size (in bytes) of a log file before switching to a
new log file. Default is 100000, minimum is 1000 and maximum is
approximately 2^30.</item>
+ <tag>RUN_ERL_DISABLE_FLOWCNTRL</tag>
+ <item>If defined, disables input and output flow control for the pty opend by run_erl.
+ Useful if you want to remove any risk of accidentally blocking the flow control
+ by hit Ctrl-S (instead of Ctrl-D to detach).
+ Which may result in blocking of the entire beam process
+ and in the case of running heart as supervisor
+ even the heart process will be blocked when writing log message to terminal.
+ Leaving the heart process unable to do its work.</item>
</taglist>
</section>
diff --git a/erts/etc/unix/run_erl.c b/erts/etc/unix/run_erl.c
index e97cc14fab..8db8e09bee 100644
--- a/erts/etc/unix/run_erl.c
+++ b/erts/etc/unix/run_erl.c
@@ -991,9 +991,7 @@ static int open_pty_master(char **ptyslave)
static int open_pty_slave(char *name)
{
int sfd;
-#ifdef DEBUG
struct termios tty_rmode;
-#endif
if ((sfd = open(name, O_RDWR, 0)) < 0) {
return -1;
@@ -1019,6 +1017,25 @@ static int open_pty_slave(char *name)
}
#endif
+ if (getenv("RUN_ERL_DISABLE_FLOWCNTRL")) {
+ if (tcgetattr(sfd, &tty_rmode) < 0) {
+ fprintf(stderr, "Cannot get terminal's current mode\n");
+ exit(-1);
+ }
+
+ tty_rmode.c_iflag &= ~IXOFF;
+ if (tcsetattr(sfd, TCSANOW, &tty_rmode) < 0) {
+ fprintf(stderr, "Cannot disable terminal's flow control on input\n");
+ exit(-1);
+ }
+
+ tty_rmode.c_iflag &= ~IXON;
+ if (tcsetattr(sfd, TCSANOW, &tty_rmode) < 0) {
+ fprintf(stderr, "Cannot disable terminal's flow control on output\n");
+ exit(-1);
+ }
+ }
+
#ifdef DEBUG
if (tcgetattr(sfd, &tty_rmode) < 0) {
fprintf(stderr, "Cannot get terminals current mode\n");
--
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