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From:   Sonny Sasaka <sonnysasaka@chromium.org>
Date:   Mon, 15 Mar 2021 10:31:32 -0700
Message-ID: <CAO271mm3N4z674GOvr3t4qBaGKaEWL=x2rMfC0O_XysjF3aCkQ@mail.gmail.com>
Subject: Re: [PATCH] Bluetooth: Cancel le_scan_restart work when stopping discovery
To:     Marcel Holtmann <marcel@holtmann.org>
Cc:     BlueZ <linux-bluetooth@vger.kernel.org>,
        Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
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Hi Marcel,

I have just sent a v2 which is rebased on bluetooth-next/master. PTAL. Thanks.


On Sat, Mar 13, 2021 at 3:00 AM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Sonny,
>
> > Not cancelling it has caused a bug where passive background scanning is
> > disabled out of the blue, preventing BLE keyboards/mice to reconnect.
> > Here is how it happens:
> > After hci_req_stop_discovery, there is still le_scan_restart_work
> > scheduled. Invocation of le_scan_restart_work causes a harmful
> > le_scan_disable_work to be scheduled. This le_scan_disable_work will
> > eventually disable passive scanning when the timer fires.
> >
> > Sample btmon trace:
> >
> > < HCI Command: LE Set Scan Parameters (0x08|0x000b) plen 7
> >        Type: Passive (0x00)
> >        Interval: 367.500 msec (0x024c)
> >        Window: 37.500 msec (0x003c)
> >        Own address type: Public (0x00)
> >        Filter policy: Accept all advertisement (0x00)
> >> HCI Event: Command Complete (0x0e) plen 4
> >      LE Set Scan Parameters (0x08|0x000b) ncmd 1
> >        Status: Success (0x00)
> > < HCI Command: LE Set Scan Enable (0x08|0x000c) plen 2
> >        Scanning: Enabled (0x01)
> >        Filter duplicates: Disabled (0x00)
> >> HCI Event: Command Complete (0x0e) plen 4
> >      LE Set Scan Enable (0x08|0x000c) ncmd 2
> >        Status: Success (0x00)
> > ...
> > < HCI Command: LE Set Scan Enable (0x08|0x000c) plen 2
> >        Scanning: Disabled (0x00)
> >        Filter duplicates: Disabled (0x00)
> >> HCI Event: Command Complete (0x0e) plen 4
> >      LE Set Scan Enable (0x08|0x000c) ncmd 2
> >        Status: Success (0x00)
> > // Background scanning is not working here onwards.
> >
> > Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
> > Signed-off-by: Sonny Sasaka <sonnysasaka@chromium.org>
> >
> > ---
> > net/bluetooth/hci_request.c | 1 +
> > 1 file changed, 1 insertion(+)
>
> I can apply this cleanly to bluetooth-next tree. Please double-check and rebase if it is still needed.
>
> Regards
>
> Marcel
>