Hi Jonas, On Fri, Jan 5, 2024 at 10:54 AM Jonas Dreßler <verdre@xxxxxxx> wrote: > > Hi Luiz, > > On 1/3/24 17:05, Luiz Augusto von Dentz wrote: > > Hi Jonas, > > > > On Tue, Jan 2, 2024 at 1:59 PM Jonas Dreßler <verdre@xxxxxxx> wrote: > >> > >> Since commit 4c67bc74f016b0d360b8573e18969c0ff7926974, we retry connecting > >> later when we get a "Command Disallowed" error returned by "Create > >> Connection". > >> > >> In this commit the intention was to retry only once, and give up if we see > >> "Command Disallowed" again on the second try. > >> > >> This made sense back then when the retry was initiated *only* from the > >> "Connect Complete" event. If we received that event, we knew that now the > >> card now must have a "free slot" for a new connection request again. These > >> days we call hci_conn_check_pending() from a few more places though, and > >> in these places we can't really be sure that there's a "free slot" on the > >> card, so the second try to "Create Connection" might fail again. > >> > >> Deal with this by being less strict about these retries and try again > >> every time we get "Command Disallowed" errors, removing the limitation to > >> only two attempts. > >> > >> Since this can potentially cause us to enter an endless cycle of > >> reconnection attempts, we'll add some guarding against that with the next > >> commit. > > > > Don't see where you are doing such guarding, besides you seem to > > assume HCI_ERROR_COMMAND_DISALLOWED would always means the controller > > is busy, or something like that, but it could perform the connection > > later, but that may not always be the case, thus why I think > > reconnecting just a few number of times is better, if you really need > > to keep retrying then this needs to be controlled by a policy in > > userspace not hardcoded in the kernel, well I can even argument that > > perhaps the initial number of reconnection shall be configurable so > > one don't have to recompile the kernel if that needs changing. > > Yes, fair enough, the next commit assumes that COMMAND_DISALLOWED always > means busy. The guarding is that we stop retrying as soon as there's no > (competing) ongoing connection attempt nor an active inquiry, which > should eventually be the case no matter what, no? > > I agree it's probably still better to not rely on this fairly complex > sanity check and keep the checking of attempts nonetheless. > > I think we could keep doing that if we check for > !hci_conn_hash_lookup_state(hdev, ACL_LINK, BT_CONNECT) && > !test_bit(HCI_INQUIRY, &hdev->flags) in hci_conn_check_pending() before > we actually retry, to make sure the retry counter doesn't get > incremented wrongly. I'll give that a try. Perhaps I'm missing something, but it should be possible to block concurrent access to HCI while a command is pending with use of hci_cmd_sync, at least on LE we do that by waiting the connection complete event so connection attempts are serialized but we don't seem to be doing the same for BR/EDR. > > > >> Signed-off-by: Jonas Dreßler <verdre@xxxxxxx> > >> --- > >> net/bluetooth/hci_event.c | 7 ++++--- > >> 1 file changed, 4 insertions(+), 3 deletions(-) > >> > >> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > >> index e8b4a0126..e1f5b6f90 100644 > >> --- a/net/bluetooth/hci_event.c > >> +++ b/net/bluetooth/hci_event.c > >> @@ -2323,12 +2323,13 @@ 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) { > >> + if (status == HCI_ERROR_COMMAND_DISALLOWED) { > >> + conn->state = BT_CONNECT2; > >> + } else { > >> conn->state = BT_CLOSED; > >> hci_connect_cfm(conn, status); > >> hci_conn_del(conn); > >> - } else > >> - conn->state = BT_CONNECT2; > >> + } > >> } > >> } else { > >> if (!conn) { > >> -- > >> 2.43.0 > >> > > > > > > Cheers, > Jonas -- Luiz Augusto von Dentz