usb: core: return -EAGAIN on usb_* functions reentrance

index 8c08aba..655d0c7 100644
@@ -274,7 +274,7 @@ static void usb_kbd_poll(struct poller_struct *poller)
 	struct usb_kbd_pdata *data = container_of(poller,
 						  struct usb_kbd_pdata, poller);
 	struct usb_device *usbdev = data->usbdev;
-	int diff, tout;
+	int diff, tout, ret;
 
 	if (data->lock)
 		return;

@@ -284,7 +284,10 @@ static void usb_kbd_poll(struct poller_struct *poller)
 		goto exit;
 	data->last_poll = get_time_ns();
 
-	if (0 > data->do_poll(data)) {
+	ret = data->do_poll(data);
+	if (ret == -EAGAIN)
+		goto exit;
+	if (ret < 0) {
 		/* exit and lock forever */
 		dev_err(&usbdev->dev,
 			"usb_submit_int_msg() failed. Keyboard disconnect?\n");

index a3fb1e8..ce229f2 100644
@@ -84,10 +84,25 @@ static void print_usb_device(struct usb_device *dev)
 
 static int host_busnum = 1;
 
+static inline int usb_host_acquire(struct usb_host *host)
+{
+	if (host->sem)
+		return -EAGAIN;
+	host->sem++;
+	return 0;
+}
+
+static inline void usb_host_release(struct usb_host *host)
+{
+	if (host->sem > 0)
+		host->sem--;
+}
+
 int usb_register_host(struct usb_host *host)
 {
 	list_add_tail(&host->list, &host_list);
 	host->busnum = host_busnum++;
+	host->sem = 0;
 	asynch_allowed = 1;
 	return 0;
 }

@@ -563,8 +578,17 @@ int usb_submit_int_msg(struct usb_device *dev, unsigned long pipe,
 			void *buffer, int transfer_len, int interval)
 {
 	struct usb_host *host = dev->host;
+	int ret;
+
+	ret = usb_host_acquire(host);
+	if (ret)
+		return ret;
+
+	ret = host->submit_int_msg(dev, pipe, buffer, transfer_len, interval);
 
-	return host->submit_int_msg(dev, pipe, buffer, transfer_len, interval);
+	usb_host_release(host);
+
+	return ret;
 }
 
 /*

@@ -590,6 +614,10 @@ int usb_control_msg(struct usb_device *dev, unsigned int pipe,
 		return -1;
 	}
 
+	ret = usb_host_acquire(host);
+	if (ret)
+		return ret;
+
 	/* set setup command */
 	setup_packet->requesttype = requesttype;
 	setup_packet->request = request;

@@ -603,6 +631,9 @@ int usb_control_msg(struct usb_device *dev, unsigned int pipe,
 
 	ret = host->submit_control_msg(dev, pipe, data, size, setup_packet,
 			timeout);
+
+	usb_host_release(host);
+
 	if (ret)
 		return ret;
 

@@ -623,8 +654,15 @@ int usb_bulk_msg(struct usb_device *dev, unsigned int pipe,
 	if (len < 0)
 		return -1;
 
+	ret = usb_host_acquire(host);
+	if (ret)
+		return ret;
+
 	dev->status = USB_ST_NOT_PROC; /* not yet processed */
 	ret = host->submit_bulk_msg(dev, pipe, data, len, timeout);
+
+	usb_host_release(host);
+
 	if (ret)
 		return ret;
 

index 8f3ce2a..aedc527 100644
@@ -152,6 +152,7 @@ struct usb_host {
 	struct device_d *hw_dev;
 	int busnum;
 	struct usb_device *root_dev;
+	int sem;
 };
 
 int usb_register_host(struct usb_host *);