USB: cdc-wdm: don't enable interrupts in USB-giveback

In the code path
  __usb_hcd_giveback_urb()
  -> wdm_in_callback()
   -> service_outstanding_interrupt()

The function service_outstanding_interrupt() will unconditionally enable
interrupts during unlock and invoke usb_submit_urb() with GFP_KERNEL.
If the HCD completes in BH (like ehci does) then the context remains
atomic due local_bh_disable() and enabling interrupts does not change
this.

Defer the error case handling to a workqueue as suggested by Oliver
Neukum. In case of an error the worker performs the read out and wakes
the user.

Fixes: c1da59dad0eb ("cdc-wdm: Clear read pipeline in case of error")
Cc: Robert Foss <robert.foss@collabora.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 24 insertions, 7 deletions

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index a0d284ef3f40..203bbd378858 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -96,6 +96,7 @@ struct wdm_device {
         struct mutex            rlock;
         wait_queue_head_t       wait;
         struct work_struct      rxwork;
+        struct work_struct      service_outs_intr;
         int                     werr;
         int                     rerr;
         int                     resp_count;
@@ -151,9 +152,6 @@ static void wdm_out_callback(struct urb *urb)
         wake_up(&desc->wait);
 }
 
-/* forward declaration */
-static int service_outstanding_interrupt(struct wdm_device *desc);
-
 static void wdm_in_callback(struct urb *urb)
 {
         struct wdm_device *desc = urb->context;
@@ -209,8 +207,6 @@ static void wdm_in_callback(struct urb *urb)
                 }
         }
 skip_error:
-        set_bit(WDM_READ, &desc->flags);
-        wake_up(&desc->wait);
 
         if (desc->rerr) {
                 /*
@@ -219,9 +215,11 @@ skip_error:
                  * We should respond to further attempts from the device to send
                  * data, so that we can get unstuck.
                  */
-                service_outstanding_interrupt(desc);
+                schedule_work(&desc->service_outs_intr);
+        } else {
+                set_bit(WDM_READ, &desc->flags);
+                wake_up(&desc->wait);
         }
-
         spin_unlock(&desc->iuspin);
 }
 
@@ -758,6 +756,21 @@ static void wdm_rxwork(struct work_struct *work)
         }
 }
 
+static void service_interrupt_work(struct work_struct *work)
+{
+        struct wdm_device *desc;
+
+        desc = container_of(work, struct wdm_device, service_outs_intr);
+
+        spin_lock_irq(&desc->iuspin);
+        service_outstanding_interrupt(desc);
+        if (!desc->resp_count) {
+                set_bit(WDM_READ, &desc->flags);
+                wake_up(&desc->wait);
+        }
+        spin_unlock_irq(&desc->iuspin);
+}
+
 /* --- hotplug --- */
 
 static int wdm_create(struct usb_interface *intf, struct usb_endpoint_descriptor *ep,
@@ -779,6 +792,7 @@ static int wdm_create(struct usb_interface *intf, struct usb_endpoint_descriptor
         desc->inum = cpu_to_le16((u16)intf->cur_altsetting->desc.bInterfaceNumber);
         desc->intf = intf;
         INIT_WORK(&desc->rxwork, wdm_rxwork);
+        INIT_WORK(&desc->service_outs_intr, service_interrupt_work);
 
         rv = -EINVAL;
         if (!usb_endpoint_is_int_in(ep))
@@ -964,6 +978,7 @@ static void wdm_disconnect(struct usb_interface *intf)
         mutex_lock(&desc->wlock);
         kill_urbs(desc);
         cancel_work_sync(&desc->rxwork);
+        cancel_work_sync(&desc->service_outs_intr);
         mutex_unlock(&desc->wlock);
         mutex_unlock(&desc->rlock);
 
@@ -1006,6 +1021,7 @@ static int wdm_suspend(struct usb_interface *intf, pm_message_t message)
                 /* callback submits work - order is essential */
                 kill_urbs(desc);
                 cancel_work_sync(&desc->rxwork);
+                cancel_work_sync(&desc->service_outs_intr);
         }
         if (!PMSG_IS_AUTO(message)) {
                 mutex_unlock(&desc->wlock);
@@ -1065,6 +1081,7 @@ static int wdm_pre_reset(struct usb_interface *intf)
         mutex_lock(&desc->wlock);
         kill_urbs(desc);
         cancel_work_sync(&desc->rxwork);
+        cancel_work_sync(&desc->service_outs_intr);
         return 0;
 }