USB: serial: fix assumption that throttle/unthrottle cannot sleep

many serial subdrivers are clearly written as if throttle/unthrottle
cannot sleep. This leads to unneeded atomic submissions. This
patch converts affected drivers in a way to makes very clear that
throttle/unthrottle can sleep. Thus future misdesigns can be avoided
and efficiency and reliability improved.

This removes any such assumption using GFP_KERNEL and spin_lock_irq()

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 6 insertions, 8 deletions

diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index ad4998bbf16..cd009cb280a 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -777,20 +777,19 @@ static void mct_u232_throttle(struct tty_struct *tty)
 {
         struct usb_serial_port *port = tty->driver_data;
         struct mct_u232_private *priv = usb_get_serial_port_data(port);
-        unsigned long flags;
         unsigned int control_state;
 
         dbg("%s - port %d", __func__, port->number);
 
-        spin_lock_irqsave(&priv->lock, flags);
+        spin_lock_irq(&priv->lock);
         priv->rx_flags |= THROTTLED;
         if (C_CRTSCTS(tty)) {
                 priv->control_state &= ~TIOCM_RTS;
                 control_state = priv->control_state;
-                spin_unlock_irqrestore(&priv->lock, flags);
+                spin_unlock_irq(&priv->lock);
                 (void) mct_u232_set_modem_ctrl(port->serial, control_state);
         } else {
-                spin_unlock_irqrestore(&priv->lock, flags);
+                spin_unlock_irq(&priv->lock);
         }
 }
 
@@ -799,20 +798,19 @@ static void mct_u232_unthrottle(struct tty_struct *tty)
 {
         struct usb_serial_port *port = tty->driver_data;
         struct mct_u232_private *priv = usb_get_serial_port_data(port);
-        unsigned long flags;
         unsigned int control_state;
 
         dbg("%s - port %d", __func__, port->number);
 
-        spin_lock_irqsave(&priv->lock, flags);
+        spin_lock_irq(&priv->lock);
         if ((priv->rx_flags & THROTTLED) && C_CRTSCTS(tty)) {
                 priv->rx_flags &= ~THROTTLED;
                 priv->control_state |= TIOCM_RTS;
                 control_state = priv->control_state;
-                spin_unlock_irqrestore(&priv->lock, flags);
+                spin_unlock_irq(&priv->lock);
                 (void) mct_u232_set_modem_ctrl(port->serial, control_state);
         } else {
-                spin_unlock_irqrestore(&priv->lock, flags);
+                spin_unlock_irq(&priv->lock);
         }
 }