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tty: Document check_tty_count() requires tty_lock held

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Holding the tty_lock() is necessary to prevent concurrent changes
to the tty count that may cause it to differ from the open file
list count. The tty_lock() is already held at all call sites.

NB: Note that the check for the pty master tty count is safe because
the slave's tty_lock() is held while decrementing the pty master
tty count.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2014-11-05 12:12:55 -05:00 committed by Greg Kroah-Hartman
parent d5e370a4ee
commit deb287e740
1 changed files with 1 additions and 0 deletions
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drivers/tty/tty_io.c
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@ -275,6 +275,7 @@ int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
return 0;
}
/* Caller must hold tty_lock */
static int check_tty_count(struct tty_struct *tty, const char *routine)
{
#ifdef CHECK_TTY_COUNT