usb: cdc-acm: fix devices not unthrottled on open

commit 6c4707f3f8c44ec18282e1c014c80e1c257042f9 upstream.

Currently CDC-ACM devices stay throttled when their TTY is closed while
throttled, stalling further communication attempts after the next open.

Unthrottling during open/activate got lost starting with kernel
3.0.0 and this patch reintroduces it.

Signed-off-by: Otto Meta <otto.patches@sister-shadow.de>
Acked-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 158f6312143..496e06e5fa6 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -498,6 +498,14 @@ static int acm_tty_open(struct tty_struct *tty, struct file *filp)
 
         usb_autopm_put_interface(acm->control);
 
+        /*
+         * Unthrottle device in case the TTY was closed while throttled.
+         */
+        spin_lock_irq(&acm->read_lock);
+        acm->throttled = 0;
+        acm->throttle_req = 0;
+        spin_unlock_irq(&acm->read_lock);
+
         if (acm_submit_read_urbs(acm, GFP_KERNEL))
                 goto bail_out;