Bluetooth: Add a new workqueue for hci_request operations

The hci_request function is blocking and cannot be called through the
usual per-HCI device workqueue (hdev->workqueue). While hci_request is
in progress any other work from the queue, including sending HCI
commands to the controller would be blocked and eventually cause the
hci_request call to time out.

This patch adds a second workqueue to be used by operations needing
hci_request and thereby avoiding issues with blocking other workqueue
users.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

include/net/bluetooth/hci_core.h

@@ -216,6 +216,7 @@ struct hci_dev {
 	unsigned long	le_last_tx;
 
 	struct workqueue_struct	*workqueue;
+	struct workqueue_struct	*req_workqueue;
 
 	struct work_struct	power_on;
 	struct delayed_work	power_off;

net/bluetooth/hci_core.c

@@ -1799,6 +1799,15 @@ int hci_register_dev(struct hci_dev *hdev)
 		goto err;
 	}
 
+	hdev->req_workqueue = alloc_workqueue(hdev->name,
+					      WQ_HIGHPRI | WQ_UNBOUND |
+					      WQ_MEM_RECLAIM, 1);
+	if (!hdev->req_workqueue) {
+		destroy_workqueue(hdev->workqueue);
+		error = -ENOMEM;
+		goto err;
+	}
+
 	error = hci_add_sysfs(hdev);
 	if (error < 0)
 		goto err_wqueue;
@@ -1827,6 +1836,7 @@ int hci_register_dev(struct hci_dev *hdev)
 
 err_wqueue:
 	destroy_workqueue(hdev->workqueue);
+	destroy_workqueue(hdev->req_workqueue);
 err:
 	ida_simple_remove(&hci_index_ida, hdev->id);
 	write_lock(&hci_dev_list_lock);
@@ -1880,6 +1890,7 @@ void hci_unregister_dev(struct hci_dev *hdev)
 	hci_del_sysfs(hdev);
 
 	destroy_workqueue(hdev->workqueue);
+	destroy_workqueue(hdev->req_workqueue);
 
 	hci_dev_lock(hdev);
 	hci_blacklist_clear(hdev);