Re: [PATCH v2 4/4] Bluetooth: Remove pending ACL connection attempts

[Jonas Dreßler]

On 1/8/24 19:44, Jonas Dreßler wrote:
> On 1/8/24 19:39, Jonas Dreßler wrote:
> > With the last commit we moved to using the hci_sync queue for "Create
> > Connection" requests, removing the need for retrying the paging after
> > finished/failed "Create Connection" requests and after the end of
> > inquiries.
> >
> > hci_conn_check_pending() was used to trigger this retry, we can remove it
> > now.
> >
> > Note that we can also remove the special handling for COMMAND_DISALLOWED
> > errors in the completion handler of "Create Connection", because "Create
> > Connection" requests are now always serialized.
> >
> > This is somewhat reverting commit 4c67bc74f016 ("[Bluetooth] Support
> > concurrent connect requests").
> >
> > With this, the BT_CONNECT2 state of ACL hci_conn objects should now be
> > back to meaning only one thing: That we received a connection request
> > from another device (see hci_conn_request_evt), but the actual connect
> > should be deferred.
> > ---
> >   include/net/bluetooth/hci_core.h |  1 -
> >   net/bluetooth/hci_conn.c         | 16 ----------------
> >   net/bluetooth/hci_event.c        | 21 ++++-----------------
> >   3 files changed, 4 insertions(+), 34 deletions(-)
> >
> > diff --git a/include/net/bluetooth/hci_core.h 
> > b/include/net/bluetooth/hci_core.h
> > index 2c30834c1..d7483958d 100644
> > --- a/include/net/bluetooth/hci_core.h
> > +++ b/include/net/bluetooth/hci_core.h
> > @@ -1330,7 +1330,6 @@ struct hci_conn *hci_conn_add(struct hci_dev 
> > *hdev, int type, bdaddr_t *dst,
> >                     u8 role);
> >   void hci_conn_del(struct hci_conn *conn);
> >   void hci_conn_hash_flush(struct hci_dev *hdev);
> > -void hci_conn_check_pending(struct hci_dev *hdev);
> >   struct hci_chan *hci_chan_create(struct hci_conn *conn);
> >   void hci_chan_del(struct hci_chan *chan);
> > diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> > index 541d55301..22033057b 100644
> > --- a/net/bluetooth/hci_conn.c
> > +++ b/net/bluetooth/hci_conn.c
> > @@ -2534,22 +2534,6 @@ void hci_conn_hash_flush(struct hci_dev *hdev)
> >       }
> >   }
> > -/* Check pending connect attempts */
> > -void hci_conn_check_pending(struct hci_dev *hdev)
> > -{
> > -    struct hci_conn *conn;
> > -
> > -    BT_DBG("hdev %s", hdev->name);
> > -
> > -    hci_dev_lock(hdev);
> > -
> > -    conn = hci_conn_hash_lookup_state(hdev, ACL_LINK, BT_CONNECT2);
> > -    if (conn)
> > -        hci_cmd_sync_queue(hdev, hci_acl_create_connection_sync, 
> > conn, NULL);
> > -
> > -    hci_dev_unlock(hdev);
> > -}
> > -
> >   static u32 get_link_mode(struct hci_conn *conn)
> >   {
> >       u32 link_mode = 0;
> > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > index e8b4a0126..91973d6d1 100644
> > --- a/net/bluetooth/hci_event.c
> > +++ b/net/bluetooth/hci_event.c
> > @@ -117,8 +117,6 @@ static u8 hci_cc_inquiry_cancel(struct hci_dev 
> > *hdev, void *data,
> >           hci_discovery_set_state(hdev, DISCOVERY_STOPPED);
> >       hci_dev_unlock(hdev);
> > -    hci_conn_check_pending(hdev);
> > -
> >       return rp->status;
> >   }
> > @@ -149,8 +147,6 @@ static u8 hci_cc_exit_periodic_inq(struct hci_dev 
> > *hdev, void *data,
> >       hci_dev_clear_flag(hdev, HCI_PERIODIC_INQ);
> > -    hci_conn_check_pending(hdev);
> > -
> >       return rp->status;
> >   }
> > @@ -2296,10 +2292,8 @@ static void hci_cs_inquiry(struct hci_dev 
> > *hdev, __u8 status)
> >   {
> >       bt_dev_dbg(hdev, "status 0x%2.2x", status);
> > -    if (status) {
> > -        hci_conn_check_pending(hdev);
> > +    if (status)
> >           return;
> > -    }
> >       set_bit(HCI_INQUIRY, &hdev->flags);
> >   }
> > @@ -2323,12 +2317,9 @@ static void hci_cs_create_conn(struct hci_dev 
> > *hdev, __u8 status)
> >       if (status) {
> >           if (conn && conn->state == BT_CONNECT) {
> > -            if (status != HCI_ERROR_COMMAND_DISALLOWED || 
> > conn->attempt > 2) {
> > -                conn->state = BT_CLOSED;
> > -                hci_connect_cfm(conn, status);
> > -                hci_conn_del(conn);
> > -            } else
> > -                conn->state = BT_CONNECT2;
> > +            conn->state = BT_CLOSED;
> > +            hci_connect_cfm(conn, status);
> > +            hci_conn_del(conn);
> >           }
> >       } else {
> >           if (!conn) {
> > @@ -3020,8 +3011,6 @@ static void hci_inquiry_complete_evt(struct 
> > hci_dev *hdev, void *data,
> >       bt_dev_dbg(hdev, "status 0x%2.2x", ev->status);
> > -    hci_conn_check_pending(hdev);
> > -
> >       if (!test_and_clear_bit(HCI_INQUIRY, &hdev->flags))
> >           return;
> > @@ -3247,8 +3236,6 @@ static void hci_conn_complete_evt(struct hci_dev 
> > *hdev, void *data,
> >   unlock:
> >       hci_dev_unlock(hdev);
> > -
> > -    hci_conn_check_pending(hdev);
> >   }
> >   static void hci_reject_conn(struct hci_dev *hdev, bdaddr_t *bdaddr)
>
> Please take a special look at this one: I'm not sure if I'm breaking the 
> functionality of deferred connecting using BT_CONNECT2 in 
> hci_conn_request_evt() here, as I don't see anywhere where we check for 
> this state and establish a connection later.
>
> It seems that this is how hci_conn_request_evt() was initially written 
> though, hci_conn_check_pending() only got introduced later and seems 
> unrelated.

Ahh nevermind... The check for BT_CONNECT2 on "Conn Complete event" got 
introduced with 4c67bc74f01 ([Bluetooth] Support concurrent connect 
requests). And later the deferred connection setup on "Conn Request 
event" got introduced with 20714bfef8 ("Bluetooth: Implement deferred 
sco socket setup").

I assume the latter commit was relying on the "Create Connection" 
request "Conn Complete event" that got introduced with the former commit 
then? That would imply that we use BT_CONNECT2 if there's already a 
"Create Connection" going on when the "Conn Request event" happens, and 
we must wait for that existing request to finish.. Is that how those 
deferred connections are supposed to work?

> Thanks,
> Jonas