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

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This reverts commit 33d4ae9885.

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 33d4ae9885 ("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: 33d4ae9885 ("drivers:tty:pty: Fix a race causing data loss on close")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Greg Kroah-Hartman 2021-03-04 17:18:02 +01:00
parent 2334de198f
commit c776b77a27
2 changed files with 4 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/tty/pty.c
View File

@ -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);
}
}

5
drivers/tty/tty_io.c
View File

@ -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