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Subject: Re: [PATCH v2] Bluetooth: Cancel le_scan_restart work when stopping
 discovery
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <20210315173059.74030-1-sonnysasaka@chromium.org>
Date:   Mon, 15 Mar 2021 21:07:35 +0100
Cc:     Bluetooth Kernel Mailing List <linux-bluetooth@vger.kernel.org>,
        Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
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Message-Id: <43E0F57D-321D-4963-B0D1-6A1C078BDC7B@holtmann.org>
References: <20210315173059.74030-1-sonnysasaka@chromium.org>
To:     Sonny Sasaka <sonnysasaka@chromium.org>
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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(+)

patch has been applied to bluetooth-next tree.

Regards

Marcel