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, 5 insertions, 7 deletions

diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index e0a8b715f2f2..a591ebec0f89 100644
--- a/drivers/usb/serial/cypress_m8.c
+++ b/drivers/usb/serial/cypress_m8.c
@@ -1155,13 +1155,12 @@ static void cypress_throttle(struct tty_struct *tty)
 {
         struct usb_serial_port *port = tty->driver_data;
         struct cypress_private *priv = usb_get_serial_port_data(port);
-        unsigned long flags;
 
         dbg("%s - port %d", __func__, port->number);
 
-        spin_lock_irqsave(&priv->lock, flags);
+        spin_lock_irq(&priv->lock);
         priv->rx_flags = THROTTLED;
-        spin_unlock_irqrestore(&priv->lock, flags);
+        spin_unlock_irq(&priv->lock);
 }
 
 
@@ -1170,14 +1169,13 @@ static void cypress_unthrottle(struct tty_struct *tty)
         struct usb_serial_port *port = tty->driver_data;
         struct cypress_private *priv = usb_get_serial_port_data(port);
         int actually_throttled, result;
-        unsigned long flags;
 
         dbg("%s - port %d", __func__, port->number);
 
-        spin_lock_irqsave(&priv->lock, flags);
+        spin_lock_irq(&priv->lock);
         actually_throttled = priv->rx_flags & ACTUALLY_THROTTLED;
         priv->rx_flags = 0;
-        spin_unlock_irqrestore(&priv->lock, flags);
+        spin_unlock_irq(&priv->lock);
 
         if (!priv->comm_is_ok)
                 return;
@@ -1185,7 +1183,7 @@ static void cypress_unthrottle(struct tty_struct *tty)
         if (actually_throttled) {
                 port->interrupt_in_urb->dev = port->serial->dev;
 
-                result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
+                result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
                 if (result) {
                         dev_err(&port->dev, "%s - failed submitting read urb, "
                                         "error %d\n", __func__, result);