tty: Convert termios_mutex to termios_rwsem
termios is commonly accessed unsafely (especially by N_TTY)
because the existing mutex forces exclusive access.
Convert existing usage.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 0fa5db4..639e24a 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -604,7 +604,7 @@
* redirect lock for undoing redirection
* file list lock for manipulating list of ttys
* tty_ldiscs_lock from called functions
- * termios_mutex resetting termios data
+ * termios_rwsem resetting termios data
* tasklist_lock to walk task list for hangup event
* ->siglock to protect ->signal/->sighand
*/
@@ -2230,7 +2230,7 @@
*
* Copies the kernel idea of the window size into the user buffer.
*
- * Locking: tty->termios_mutex is taken to ensure the winsize data
+ * Locking: tty->termios_rwsem is taken to ensure the winsize data
* is consistent.
*/
@@ -2238,9 +2238,9 @@
{
int err;
- mutex_lock(&tty->termios_mutex);
+ down_read(&tty->termios_rwsem);
err = copy_to_user(arg, &tty->winsize, sizeof(*arg));
- mutex_unlock(&tty->termios_mutex);
+ up_read(&tty->termios_rwsem);
return err ? -EFAULT: 0;
}
@@ -2261,7 +2261,7 @@
unsigned long flags;
/* Lock the tty */
- mutex_lock(&tty->termios_mutex);
+ down_write(&tty->termios_rwsem);
if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
goto done;
/* Get the PID values and reference them so we can
@@ -2276,7 +2276,7 @@
tty->winsize = *ws;
done:
- mutex_unlock(&tty->termios_mutex);
+ up_write(&tty->termios_rwsem);
return 0;
}
EXPORT_SYMBOL(tty_do_resize);
@@ -3015,7 +3015,7 @@
tty->session = NULL;
tty->pgrp = NULL;
mutex_init(&tty->legacy_mutex);
- mutex_init(&tty->termios_mutex);
+ init_rwsem(&tty->termios_rwsem);
init_ldsem(&tty->ldisc_sem);
init_waitqueue_head(&tty->write_wait);
init_waitqueue_head(&tty->read_wait);