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Commit 37b16457 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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tty: Fix high cpu load if tty is unreleaseable 



Kernel oops can cause the tty to be unreleaseable (for example, if
n_tty_read() crashes while on the read_wait queue). This will cause
tty_release() to endlessly loop without sleeping.

Use a killable sleep timeout which grows by 2n+1 jiffies over the interval
[0, 120 secs.) and then jumps to forever (but still killable).

NB: killable just allows for the task to be rewoken manually, not
to be terminated.

Cc: <stable@vger.kernel.org> # since before 2.6.32
Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 547039ec

drivers/tty/tty_io.c

+6 −1
Original line number Original line Diff line number Diff line
@@ -1709,6 +1709,7 @@ int tty_release(struct inode *inode, struct file *filp) 
	int	pty_master, tty_closing, o_tty_closing, do_sleep;

	int	pty_master, tty_closing, o_tty_closing, do_sleep;

	int	idx;

	int	idx;

	char	buf[64];

	char	buf[64];

	long	timeout = 0;





	if (tty_paranoia_check(tty, inode, __func__))

	if (tty_paranoia_check(tty, inode, __func__))

		return 0;

		return 0;
@@ -1793,7 +1794,11 @@ int tty_release(struct inode *inode, struct file *filp) 
				__func__, tty_name(tty, buf));

				__func__, tty_name(tty, buf));

		tty_unlock_pair(tty, o_tty);

		tty_unlock_pair(tty, o_tty);

		mutex_unlock(&tty_mutex);

		mutex_unlock(&tty_mutex);

		schedule();

		schedule_timeout_killable(timeout);

		if (timeout < 120 * HZ)

			timeout = 2 * timeout + 1;

		else

			timeout = MAX_SCHEDULE_TIMEOUT;

	}

	}





	/*

	/*