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Date: Mon, 8 Jan 2024 19:55:27 +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 19:44, 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
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