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author | Jiri Slaby <jslaby@suse.cz> | 2011-08-10 14:59:28 +0200 |
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committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-08-23 10:10:38 -0700 |
commit | 24d406a6bf736f7aebdc8fa0f0ec86e0890c6d24 (patch) | |
tree | 3dfb2053f7785508304fd29d6c1bb6e6a42a7d5c /drivers/tty/tty_io.c | |
parent | dbb3b1ca5609d1f3848cd387d06cc60aaacf7f98 (diff) | |
download | op-kernel-dev-24d406a6bf736f7aebdc8fa0f0ec86e0890c6d24.zip op-kernel-dev-24d406a6bf736f7aebdc8fa0f0ec86e0890c6d24.tar.gz |
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 'drivers/tty/tty_io.c')
-rw-r--r-- | drivers/tty/tty_io.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 150e4f7..4f1fc81 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1295,8 +1295,7 @@ static int tty_driver_install_tty(struct tty_driver *driver, * * Locking: tty_mutex for now */ -static void tty_driver_remove_tty(struct tty_driver *driver, - struct tty_struct *tty) +void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct *tty) { if (driver->ops->remove) driver->ops->remove(driver, tty); |