linux-kernel - [PATCH] ktest: restore tty settings after closing console

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Date:	Tue, 27 Jan 2015 12:10:04 -0600
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Satoru Takeuchi <satoru.takeuchi@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] ktest: restore tty settings after closing console

When ktest runs the console program as a child process, the parent and
child share the same tty for stdin and stderr.  This is problematic when
using a libvirt target.  The "virsh console" program makes a lot of
changes to the tty settings, making ktest's output hard to read
(carriage returns don't work).  After ktest exits, the terminal is
unusable (CRs broken, stdin isn't echoed).

I think the best way to fix this issue would be to create a
pseudoterminal (pty pair) so the child process would have a dedicated
tty, and then use pipes to connect the two ttys.  I'm not sure if that's
overkill, but it's far beyond my current Perl abilities.

This patch is a much easier way to (partially) fix this issue.  It saves
the tty settings before opening the console and restores them after
closing it.  There are still a few places where ktest prints mangled
output while the console is open, but the output is much more legible
overall, and the terminal works just fine after ktest exits.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 tools/testing/ktest/ktest.pl | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/testing/ktest/ktest.pl b/tools/testing/ktest/ktest.pl
index b9cd036..ba20f89 100755
--- a/tools/testing/ktest/ktest.pl
+++ b/tools/testing/ktest/ktest.pl
@@ -178,6 +178,7 @@ my $checkout;
 my $localversion;
 my $iteration = 0;
 my $successes = 0;
+my $stty;

 my $bisect_good;
 my $bisect_bad;
@@ -1349,6 +1350,9 @@ sub open_console {

     my $flags;

+    # save terminal settings
+    $stty = `stty -g`;
+
     my $pid = open($fp, "$console|") or
 	dodie "Can't open console $console";

@@ -1368,6 +1372,9 @@ sub close_console {

     print "closing!\n";
     close($fp);
+
+    # restore terminal settings
+    system("stty $stty");
 }

 sub start_monitor {
-- 
2.1.0

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