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authorArnd Bergmann <arnd@arndb.de>2010-06-18 14:58:07 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-10 13:47:44 -0700
commit11dbf203922dc70a340417c895c95fb96f6b7068 (patch)
tree7c79b79c74a184a7d67d3f54af4e37dee930d11e /drivers/char
parenta0821df6e57c8af0053963d0d08c8d5198ea077d (diff)
downloadop-kernel-dev-11dbf203922dc70a340417c895c95fb96f6b7068.zip
op-kernel-dev-11dbf203922dc70a340417c895c95fb96f6b7068.tar.gz
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>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/pty.c4
-rw-r--r--drivers/char/tty_io.c24
2 files changed, 15 insertions, 13 deletions
diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index f2d7a76..ad46eae 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -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();
}
}
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index dcf7d36..4c4030c 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -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) {
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