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Bluetooth: remove unneeded hci_conn_hold/put_device()

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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 <dh.herrmann@gmail.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
This commit is contained in:
David Herrmann 2013-04-06 20:28:38 +02:00 committed by Gustavo Padovan
parent 93796fa6f2
commit fc225c3f5d
4 changed files with 4 additions and 41 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
include/net/bluetooth/hci_core.h
View file

@ -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));

17
net/bluetooth/hci_conn.c
View file

@ -410,8 +410,6 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst)
if (hdev->notify)
hdev->notify(hdev, HCI_NOTIFY_CONN_ADD);
atomic_set(&conn->devref, 0);
hci_conn_init_sysfs(conn);
return conn;
@ -460,7 +458,7 @@ int hci_conn_del(struct hci_conn *conn)
skb_queue_purge(&conn->data_q);
hci_conn_put_device(conn);
hci_conn_del_sysfs(conn);
hci_dev_put(hdev);
@ -847,19 +845,6 @@ void hci_conn_check_pending(struct hci_dev *hdev)
hci_dev_unlock(hdev);
}
void hci_conn_hold_device(struct hci_conn *conn)
{
atomic_inc(&conn->devref);
}
EXPORT_SYMBOL(hci_conn_hold_device);
void hci_conn_put_device(struct hci_conn *conn)
{
if (atomic_dec_and_test(&conn->devref))
hci_conn_del_sysfs(conn);
}
EXPORT_SYMBOL(hci_conn_put_device);
int hci_get_conn_list(void __user *arg)
{
struct hci_conn *c;

4
net/bluetooth/hci_event.c
View file

@ -1706,7 +1706,6 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, struct sk_buff *skb)
} else
conn->state = BT_CONNECTED;
hci_conn_hold_device(conn);
hci_conn_add_sysfs(conn);
if (test_bit(HCI_AUTH, &hdev->flags))
@ -2987,7 +2986,6 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev,
conn->handle = __le16_to_cpu(ev->handle);
conn->state = BT_CONNECTED;
hci_conn_hold_device(conn);
hci_conn_add_sysfs(conn);
break;
@ -3452,7 +3450,6 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
hcon->disc_timeout = HCI_DISCONN_TIMEOUT;
hci_conn_drop(hcon);
hci_conn_hold_device(hcon);
hci_conn_add_sysfs(hcon);
amp_physical_cfm(bredr_hcon, hcon);
@ -3586,7 +3583,6 @@ static void hci_le_conn_complete_evt(struct hci_dev *hdev, struct sk_buff *skb)
conn->handle = __le16_to_cpu(ev->handle);
conn->state = BT_CONNECTED;
hci_conn_hold_device(conn);
hci_conn_add_sysfs(conn);
hci_proto_connect_cfm(conn, ev->status);

20
net/bluetooth/hidp/core.c
View file

@ -73,18 +73,6 @@ static struct hidp_session *__hidp_get_session(bdaddr_t *bdaddr)
return NULL;
}
static void __hidp_link_session(struct hidp_session *session)
{
list_add(&session->list, &hidp_session_list);
}
static void __hidp_unlink_session(struct hidp_session *session)
{
hci_conn_put_device(session->conn);
list_del(&session->list);
}
static void __hidp_copy_session(struct hidp_session *session, struct hidp_conninfo *ci)
{
memset(ci, 0, sizeof(*ci));
@ -760,7 +748,7 @@ static int hidp_session(void *arg)
fput(session->ctrl_sock->file);
__hidp_unlink_session(session);
list_del(&session->list);
up_write(&hidp_session_sem);
@ -783,8 +771,6 @@ static struct hci_conn *hidp_get_connection(struct hidp_session *session)
hci_dev_lock(hdev);
conn = hci_conn_hash_lookup_ba(hdev, ACL_LINK, dst);
if (conn)
hci_conn_hold_device(conn);
hci_dev_unlock(hdev);
hci_dev_put(hdev);
@ -1026,7 +1012,7 @@ int hidp_add_connection(struct hidp_connadd_req *req, struct socket *ctrl_sock,
session->flags = req->flags & (1 << HIDP_BLUETOOTH_VENDOR_ID);
session->idle_to = req->idle_to;
__hidp_link_session(session);
list_add(&session->list, &hidp_session_list);
if (req->rd_size > 0) {
err = hidp_setup_hid(session, req);
@ -1106,7 +1092,7 @@ int hidp_add_connection(struct hidp_connadd_req *req, struct socket *ctrl_sock,
session->rd_data = NULL;
purge:
__hidp_unlink_session(session);
list_del(&session->list);
skb_queue_purge(&session->ctrl_transmit);
skb_queue_purge(&session->intr_transmit);