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| author | Jiri Slaby <jslaby@suse.cz> | 2011-08-10 16:59:28 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-08-23 21:10:38 +0400 |
| commit | 24d406a6bf736f7aebdc8fa0f0ec86e0890c6d24 (patch) | |
| tree | 3dfb2053f7785508304fd29d6c1bb6e6a42a7d5c /include/linux | |
| parent | dbb3b1ca5609d1f3848cd387d06cc60aaacf7f98 (diff) | |
| download | linux-24d406a6bf736f7aebdc8fa0f0ec86e0890c6d24.tar.xz | |
TTY: pty, fix pty counting
tty_operations->remove is normally called like:
queue_release_one_tty
->tty_shutdown
->tty_driver_remove_tty
->tty_operations->remove
However tty_shutdown() is called from queue_release_one_tty() only if
tty_operations->shutdown is NULL. But for pty, it is not.
pty_unix98_shutdown() is used there as ->shutdown.
So tty_operations->remove of pty (i.e. pty_unix98_remove()) is never
called. This results in invalid pty_count. I.e. what can be seen in
/proc/sys/kernel/pty/nr.
I see this was already reported at:
https://lkml.org/lkml/2009/11/5/370
But it was not fixed since then.
This patch is kind of a hackish way. The problem lies in ->install. We
allocate there another tty (so-called tty->link). So ->install is
called once, but ->remove twice, for both tty and tty->link. The fix
here is to count both tty and tty->link and divide the count by 2 for
user.
And to have ->remove called, let's make tty_driver_remove_tty() global
and call that from pty_unix98_shutdown() (tty_operations->shutdown).
While at it, let's document that when ->shutdown is defined,
tty_shutdown() is not called.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/tty.h | 2 | ||||
| -rw-r--r-- | include/linux/tty_driver.h | 3 |
2 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index 44bc0c5617e1..5f2ede82b3d6 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -421,6 +421,8 @@ extern void tty_driver_flush_buffer(struct tty_struct *tty); extern void tty_throttle(struct tty_struct *tty); extern void tty_unthrottle(struct tty_struct *tty); extern int tty_do_resize(struct tty_struct *tty, struct winsize *ws); +extern void tty_driver_remove_tty(struct tty_driver *driver, + struct tty_struct *tty); extern void tty_shutdown(struct tty_struct *tty); extern void tty_free_termios(struct tty_struct *tty); extern int is_current_pgrp_orphaned(void); diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h index 9deeac855240..ecdaeb98b293 100644 --- a/include/linux/tty_driver.h +++ b/include/linux/tty_driver.h @@ -47,6 +47,9 @@ * * This routine is called synchronously when a particular tty device * is closed for the last time freeing up the resources. + * Note that tty_shutdown() is not called if ops->shutdown is defined. + * This means one is responsible to take care of calling ops->remove (e.g. + * via tty_driver_remove_tty) and releasing tty->termios. * * * void (*cleanup)(struct tty_struct * tty); |