[PATCH] tty: clarify disassociate_ctty

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Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=680a96710041c3c25464b5e093b80ca43cb94f52
Commit:     680a96710041c3c25464b5e093b80ca43cb94f52
Parent:     cdc623300841bc8f1625c320d5a6cbc52c43c60d
Author:     Eric W. Biederman <[EMAIL PROTECTED]>
AuthorDate: Mon Feb 12 00:52:52 2007 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Mon Feb 12 09:48:31 2007 -0800

    [PATCH] tty: clarify disassociate_ctty
    
    The code to look at tty_old_pgrp and send SIGHUP and SIGCONT when it is
    present only executes when disassociate_ctty is called from do_exit.  Make
    this clear by adding an explict on_exit check, and explicitly setting
    tty_old_pgrp to 0.
    
    In addition fix the locking by reading tty_old_pgrp under the siglock.
    
    Signed-off-by: Eric W. Biederman <[EMAIL PROTECTED]>
    Cc: Alan Cox <[EMAIL PROTECTED]>
    Cc: Oleg Nesterov <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 drivers/char/tty_io.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index b9fce77..ac937f7 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1508,8 +1508,12 @@ void disassociate_ctty(int on_exit)
                /* XXX: here we race, there is nothing protecting tty */
                if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
                        tty_vhangup(tty);
-       } else {
-               pid_t old_pgrp = current->signal->tty_old_pgrp;
+       } else if (on_exit) {
+               pid_t old_pgrp;
+               spin_lock_irq(&current->sighand->siglock);
+               old_pgrp = current->signal->tty_old_pgrp;
+               current->signal->tty_old_pgrp = 0;
+               spin_unlock_irq(&current->sighand->siglock);
                if (old_pgrp) {
                        kill_pg(old_pgrp, SIGHUP, on_exit);
                        kill_pg(old_pgrp, SIGCONT, on_exit);
-
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