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tty: avoid recursive BTM in pty_close 

When the console has been redirected, a hangup of the tty
will cause tty_release to be called under the big tty_mutex,
which leads to a deadlock because hangup is also called
under the BTM.

This moves the BTM deeper into the tty_hangup function so
we can close the redirected tty without holding the BTM.
In case of pty, we now need to drop the BTM before
calling tty_vhangup.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Arnd Bergmann 2010-06-18 14:58:07 +02:00 committed by Greg Kroah-Hartman
parent a0821df6e5
commit 11dbf20392
2 changed files with 15 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/char/pty.c
View File

@ -62,7 +62,9 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
if (tty->driver == ptm_driver)
devpts_pty_kill(tty->link);
#endif
tty_vhangup_locked(tty->link);
tty_unlock();
tty_vhangup(tty->link);
tty_lock();
}
}

24
drivers/char/tty_io.c
View File

@ -471,7 +471,7 @@ void tty_wakeup(struct tty_struct *tty)
EXPORT_SYMBOL_GPL(tty_wakeup);
/**
* do_tty_hangup - actual handler for hangup events
* __tty_hangup - actual handler for hangup events
* @work: tty device
*
* This can be called by the "eventd" kernel thread. That is process
@ -492,7 +492,7 @@ EXPORT_SYMBOL_GPL(tty_wakeup);
* tasklist_lock to walk task list for hangup event
* ->siglock to protect ->signal/->sighand
*/
void tty_vhangup_locked(struct tty_struct *tty)
void __tty_hangup(struct tty_struct *tty)
{
struct file *cons_filp = NULL;
struct file *filp, *f = NULL;
@ -512,10 +512,12 @@ void tty_vhangup_locked(struct tty_struct *tty)
}
spin_unlock(&redirect_lock);
tty_lock();
/* inuse_filps is protected by the single tty lock,
this really needs to change if we want to flush the
workqueue with the lock held */
check_tty_count(tty, "do_tty_hangup");
check_tty_count(tty, "tty_hangup");
file_list_lock();
/* This breaks for file handles being sent over AF_UNIX sockets ? */
@ -594,6 +596,9 @@ void tty_vhangup_locked(struct tty_struct *tty)
*/
set_bit(TTY_HUPPED, &tty->flags);
tty_ldisc_enable(tty);
tty_unlock();
if (f)
fput(f);
}
@ -603,9 +608,7 @@ static void do_tty_hangup(struct work_struct *work)
struct tty_struct *tty =
container_of(work, struct tty_struct, hangup_work);
tty_lock();
tty_vhangup_locked(tty);
tty_unlock();
__tty_hangup(tty);
}
/**
@ -643,13 +646,12 @@ void tty_vhangup(struct tty_struct *tty)
printk(KERN_DEBUG "%s vhangup...\n", tty_name(tty, buf));
#endif
tty_lock();
tty_vhangup_locked(tty);
tty_unlock();
__tty_hangup(tty);
}
EXPORT_SYMBOL(tty_vhangup);
/**
* tty_vhangup_self - process vhangup for own ctty
*
@ -727,10 +729,8 @@ void disassociate_ctty(int on_exit)
if (tty) {
tty_pgrp = get_pid(tty->pgrp);
if (on_exit) {
tty_lock();
if (tty->driver->type != TTY_DRIVER_TYPE_PTY)
tty_vhangup_locked(tty);
tty_unlock();
tty_vhangup(tty);
}
tty_kref_put(tty);
} else if (on_exit) {