Re: [PATCH v2] Bluetooth: hci_event: fix simultaneous discovery stuck in FINDING

[Jiajia Liu]

On Tue, Jun 02, 2026 at 11:53:29PM +0200, Paul Menzel wrote:
> [Cc: -brian.gix@xxxxxxxxx (bouncing)]
> 
> Dear Luiz,
> 
> 
> Am 02.06.26 um 18:43 schrieb Luiz Augusto von Dentz:
> 
> > On Tue, Jun 2, 2026 at 10:41 AM Paul Menzel <pmenzel@xxxxxxxxxxxxx> wrote:
> 
> > > Am 02.06.26 um 09:00 schrieb Jiajia Liu:
> > > > When hci_inquiry_complete_evt is called between le_scan_disable and
> > > > le_set_scan_enable_complete and no remote name needs to be resolved,
> > > > the interleaved discovery with SIMULTANEOUS quirk gets stuck in
> > > > DISCOVERY_FINDING. le_set_scan_enable_complete does not check inquiry
> > > > state. No one sets DISCOVERY_STOPPED in this process.
> > > > 
> > > > Add state check in le_set_scan_enable_complete and change state if
> > > > the state is DISCOVERY_FINDING. Tested with AX201 (8087:0026) in Dell
> > > 
> > > … change state to DISCOVERY_STOPPED …
> > > 
> > > I’d add a new paragraph for the Tested part.
> > > 
> > > > Vostro 13. Discovering disabled MGMT Event below is reported when
> > > > running into the above condition.
> > > 
> > > Thank you for sharing the test device. Could you please document how to
> > > get into this state exactly? Some Xiaomi device?
> > 
> > What are you talking about here by saying Xiaomi device? He literally
> > said Dell Vostro 13, a laptop, and this is a local only procedure,
> > there is no remote device involved here.
> 
> In the trace below a Xiaomi device shows up, if I am not mistaken.

There should be no requirements for Bluetooth devices. To keep the serial
number of packet continuous, I didn't remove the Device Found MGMT Event.
It looks like someone's TV device.

The producer is Open the bluetooth panel of gnome-control-center and wait.
If the device list on the pannel is not flushed again and becomes empty,
it probably gets into this state. btmon or dynamic debug of
hci_discovery_set_state can confirm the state.

It think it depends on the timing of Inquiry Complete Event. There is a
very small time slot between disabling LE scan and disabling completion.
If Inquiry Complete Event arrives in the slot, there is a chance to hit
the state.

> 
> > > >    @ MGMT Command: Start Discovery (0x0023)    {0x0001} [hci0] 10885.970873
> > > >            Address type: 0x07
> > > >              BR/EDR
> > > >              LE Public
> > > >              LE Random
> > > >    ...
> > > >    < HCI Command: LE Set Extended Scan Enable    #38205 [hci0] 10886.131438
> > > >            Extended scan: Enabled (0x01)
> > > >            Filter duplicates: Enabled (0x01)
> > > >            Duration: 0 msec (0x0000)
> > > >            Period: 0.00 sec (0x0000)
> > > >    > HCI Event: Command Complete (0x0e) plen 4   #38206 [hci0] 10886.133295
> > > >          LE Set Extended Scan Enable (0x08|0x0042) ncmd 2
> > > >            Status: Success (0x00)
> > > >    @ MGMT Event: Discovering (0x0013) plen 2   {0x0001} [hci0] 10886.133414
> > > >            Address type: 0x07
> > > >              BR/EDR
> > > >              LE Public
> > > >              LE Random
> > > >            Discovery: Enabled (0x01)
> > > >    < HCI Command: Inquiry (0x01|0x0001) plen 5   #38207 [hci0] 10886.133528
> > > >            Access code: 0x9e8b33 (General Inquiry)
> > > >            Length: 10.24s (0x08)
> > > >            Num responses: 0
> > > >    > HCI Event: Command Status (0x0f) plen 4     #38208 [hci0] 10886.141333
> > > >          Inquiry (0x01|0x0001) ncmd 2
> > > >            Status: Success (0x00)
> > > >    ...
> > > >    < HCI Command: LE Set Extended Scan Enable    #38242 [hci0] 10896.381802
> > > >            Extended scan: Disabled (0x00)
> > > >            Filter duplicates: Disabled (0x00)
> > > >            Duration: 0 msec (0x0000)
> > > >            Period: 0.00 sec (0x0000)
> > > >    > HCI Event: Inquiry Complete (0x01) plen 1   #38243 [hci0] 10896.383419
> > > >            Status: Success (0x00)
> > > >    > HCI Event: Command Complete (0x0e) plen 4   #38244 [hci0] 10896.394378
> > > >          LE Set Extended Scan Enable (0x08|0x0042) ncmd 2
> > > >            Status: Success (0x00)
> > > >    @ MGMT Event: Device Found (0x0012) plen 22 {0x0001} [hci0] 10896.394497
> > > >            LE Address: 88:12:AC:92:43:69
> > > >            RSSI: -101 dBm (0x9b)
> > > >            Flags: 0x00000004
> > > >              Not Connectable
> > > >            Data length: 8
> > > >            Company: Xiaomi Inc. (911)
> > > >              Data[0]:
> > > >            16-bit Service UUIDs (complete): 1 entry
> > > >              Xiaomi Inc. (0xfdaa)
> > > >    @ MGMT Event: Discovering (0x0013) plen 2   {0x0001} [hci0] 10896.394506
> > > >            Address type: 0x07
> > > >              BR/EDR
> > > >              LE Public
> > > >              LE Random
> > > >            Discovery: Disabled (0x00)
> > > > 
> > > > Fixes: 8ffde2a73f2c ("Bluetooth: Convert le_scan_disable timeout to hci_sync")
> > > > Signed-off-by: Jiajia Liu <liujiajia@xxxxxxxxxx>
> > > > ---
> > > > 
> > > > Changes in v2:
> > > > - move the handler to hci_event.c
> > > > - remove unnecessary bt_dev_dbg
> > > > - update commit message
> > > > 
> > > > ---
> > > >    net/bluetooth/hci_event.c | 7 +++++++
> > > >    1 file changed, 7 insertions(+)
> > > > 
> > > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > > > index eea2f810aafa..1cd5f97daafe 100644
> > > > --- a/net/bluetooth/hci_event.c
> > > > +++ b/net/bluetooth/hci_event.c
> > > > @@ -1769,6 +1769,13 @@ static void le_set_scan_enable_complete(struct hci_dev *hdev, u8 enable)
> > > > 
> > > >                hci_dev_clear_flag(hdev, HCI_LE_SCAN);
> > > > 
> > > > +             if (hdev->discovery.type == DISCOV_TYPE_INTERLEAVED &&
> > > > +                 hci_test_quirk(hdev, HCI_QUIRK_SIMULTANEOUS_DISCOVERY) &&
> > > > +                 !test_bit(HCI_INQUIRY, &hdev->flags) &&
> > > > +                 hdev->discovery.state == DISCOVERY_FINDING) {
> > > > +                     hci_discovery_set_state(hdev, DISCOVERY_STOPPED);
> > > > +             }
> > > > +
> > > >                /* The HCI_LE_SCAN_INTERRUPTED flag indicates that we
> > > >                 * interrupted scanning due to a connect request. Mark
> > > >                 * therefore discovery as stopped.
> 
> 
> Kind regards,
> 
> Paul