Commit c776b77a authored by Greg Kroah-Hartman's avatar Greg Kroah-Hartman
Browse files

Revert "drivers:tty:pty: Fix a race causing data loss on close" 



This reverts commit 33d4ae98.

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 33d4ae98 ("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: default avatarPierre-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: 33d4ae98 ("drivers:tty:pty: Fix a race causing data loss on close")
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2334de19

drivers/tty/pty.c

+2 −13
Original line number Diff line number Diff line
@@ -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);

	}

}

drivers/tty/tty_io.c

+2 −3
Original line number Diff line number Diff line
@@ -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