From fc225c3f5d1b6aa6f99c5c300af4605e4923ce79 Mon Sep 17 00:00:00 2001 From: David Herrmann Date: Sat, 6 Apr 2013 20:28:38 +0200 Subject: Bluetooth: remove unneeded hci_conn_hold/put_device() hci_conn_hold/put_device() is used to control when hci_conn->dev is no longer needed and can be deleted from the system. Lets first look how they are currently used throughout the code (excluding HIDP!). All code that uses hci_conn_hold_device() looks like this: ... hci_conn_hold_device(); hci_conn_add_sysfs(); ... On the other side, hci_conn_put_device() is exclusively used in hci_conn_del(). So, considering that hci_conn_del() must not be called twice (which would fail horribly), we know that hci_conn_put_device() is only called _once_ (which is in hci_conn_del()). On the other hand, hci_conn_add_sysfs() must not be called twice, either (it would call device_add twice, which breaks the device, see drivers/base/core.c). So we know that hci_conn_hold_device() is also called only once (it's only called directly before hci_conn_add_sysfs()). So hold and put are known to be called only once. That means we can safely remove them and directly call hci_conn_del_sysfs() in hci_conn_del(). But there is one issue left: HIDP also uses hci_conn_hold/put_device(). However, this case can be ignored and simply removed as it is totally broken. The issue is, the only thing HIDP delays with hci_conn_hold_device() is the removal of the hci_conn->dev from sysfs. But, the hci_conn device has no mechanism to get notified when its own parent (hci_dev) gets removed from sysfs. hci_dev_hold/put() does _not_ control when it is removed but only when the device object is created and destroyed. And hci_dev calls hci_conn_flush_*() when it removes itself from sysfs, which itself causes hci_conn_del() to be called, but it does _not_ cause hci_conn_del_sysfs() to be called, which is wrong. Hence, we fix it to call hci_conn_del_sysfs() in hci_conn_del(). This guarantees that a hci_conn object is removed from sysfs _before_ its parent hci_dev is removed. The changes to HIDP look scary, wrong and broken. However, if you look at the HIDP session management, you will notice they're already broken in the exact _same_ way (ever tried "unplugging" HIDP devices? Breaks _all_ the time). So this patch only makes HIDP look _scary_ and _obviously broken_. It does not break HIDP itself, it already is! See later patches in this series which fix HIDP to use proper session-management. Signed-off-by: David Herrmann Acked-by: Marcel Holtmann Signed-off-by: Gustavo Padovan --- include/net/bluetooth/hci_core.h | 4 ---- 1 file changed, 4 deletions(-) (limited to 'include/net') diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h index 78ea9c7c202c..5590cc4412c6 100644 --- a/include/net/bluetooth/hci_core.h +++ b/include/net/bluetooth/hci_core.h @@ -345,7 +345,6 @@ struct hci_conn { struct timer_list auto_accept_timer; struct device dev; - atomic_t devref; struct hci_dev *hdev; void *l2cap_data; @@ -601,9 +600,6 @@ int hci_conn_switch_role(struct hci_conn *conn, __u8 role); void hci_conn_enter_active_mode(struct hci_conn *conn, __u8 force_active); -void hci_conn_hold_device(struct hci_conn *conn); -void hci_conn_put_device(struct hci_conn *conn); - static inline void hci_conn_hold(struct hci_conn *conn) { BT_DBG("hcon %p orig refcnt %d", conn, atomic_read(&conn->refcnt)); -- cgit v1.2.3