From c776b77a279c327fe9e7710e71a3400766554255 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Thu, 4 Mar 2021 17:18:02 +0100
Subject: [PATCH] Revert "drivers:tty:pty: Fix a race causing data loss on
close"
This reverts commit 33d4ae98859873ddd49e22e4ca724387548b3d89.
Pierre-Louis writes:
Our SOF/audio CI shows an across-the-board regression when we try v5.12-rc1,
specifically on pause/resume tests with an interactive terminal running 'aplay
-i' commands managed by expect to simulate the user pressing the space bar to
pause/unpause. It turns out the processes are not longer killed and the audio
devices remain busy (see publicly available test results listed below).
git bisect points to commit 33d4ae9885987 ("drivers:tty:pty: Fix a race
causing data loss on close"). Reverting the patch fixes the issue on all test
devices.
Further analysis with Corey Minyard points to a problem where a slave tty will
not get a SIGHUP when the master is closed.
So revert this for now:
Reported-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/00154592-c5ee-aaba-956e-b265473b53bc@linux.intel.com
Cc: Corey Minyard <cminyard@mvista.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Mark Brown <broonie@kernel.org>,
Fixes: 33d4ae988598 ("drivers:tty:pty: Fix a race causing data loss on close")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/pty.c | 15 ++-------------
drivers/tty/tty_io.c | 5 ++---
2 files changed, 4 insertions(+), 16 deletions(-)
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 8b2797b6ee441..5e2374580e271 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -66,8 +66,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
wake_up_interruptible(&tty->link->read_wait);
wake_up_interruptible(&tty->link->write_wait);
if (tty->driver->subtype == PTY_TYPE_MASTER) {
- struct file *f;
-
+ set_bit(TTY_OTHER_CLOSED, &tty->flags);
#ifdef CONFIG_UNIX98_PTYS
if (tty->driver == ptm_driver) {
mutex_lock(&devpts_mutex);
@@ -76,17 +75,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
mutex_unlock(&devpts_mutex);
}
#endif
-
- /*
- * This hack is required because a program can open a
- * pty and redirect a console to it, but if the pty is
- * closed and the console is not released, then the
- * slave side will never close. So release the
- * redirect when the master closes.
- */
- f = tty_release_redirect(tty->link);
- if (f)
- fput(f);
+ tty_vhangup(tty->link);
}
}
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 74733ec8f5653..391bada4cedb6 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -544,9 +544,7 @@ EXPORT_SYMBOL_GPL(tty_wakeup);
* @tty: tty device
*
* This is available to the pty code so if the master closes, if the
- * slave is a redirect it can release the redirect. It returns the
- * filp for the redirect, which must be fput when the operations on
- * the tty are completed.
+ * slave is a redirect it can release the redirect.
*/
struct file *tty_release_redirect(struct tty_struct *tty)
{
@@ -561,6 +559,7 @@ struct file *tty_release_redirect(struct tty_struct *tty)
return f;
}
+EXPORT_SYMBOL_GPL(tty_release_redirect);
/**
* __tty_hangup - actual handler for hangup events
--
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