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

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Date: Mon, 8 Jan 2024 19:44:42 +0100
From: Jonas Dreßler <verdre@...d.nl>
To: Marcel Holtmann <marcel@...tmann.org>,
 Johan Hedberg <johan.hedberg@...il.com>,
 Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc: linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, verdre@...d.nl
Subject: Re: [PATCH v2 4/4] Bluetooth: Remove pending ACL connection attempts

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.

Thanks,
Jonas