linux-kernel - Re: [PATCH v2] Bluetooth: hci_uart: fix race during initialization

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Message-ID: <b7fdaca1-b127-71c2-3286-2dd68b59f746@salutedevices.com>
Date: Thu, 19 Dec 2024 23:07:22 +0300
From: Arseniy Krasnov <avkrasnov@...utedevices.com>
To: Luiz Augusto von Dentz <luiz.dentz@...il.com>
CC: Marcel Holtmann <marcel@...tmann.org>, <oxffffaa@...il.com>,
	<linux-bluetooth@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kernel@...utedevices.com>
Subject: Re: [PATCH v2] Bluetooth: hci_uart: fix race during initialization



On 19.12.2024 22:01, Luiz Augusto von Dentz wrote:
> Hi Arseniy,
> 
> On Thu, Dec 19, 2024 at 1:42 PM Arseniy Krasnov
> <avkrasnov@...utedevices.com> wrote:
>>
>> Hi, sorry i'm new in bluetooth subsystem. I get the following
>> message from CI:
>> https://patchwork.kernel.org/project/bluetooth/list/?series=918554
>> Where one of tests was failed. Where I can get more information
>> about failure:
>>
>> tedd_an/TestRunner_mgmt-tester  fail    TestRunner_mgmt-tester: Total: 490, Passed: 483 (98.6%), Failed: 3, Not Run: 4
> 
> These looks like a false positives, your changes should affect the
> tests since that run with hci_vhci driver, not the uart ones.

Got it,

Thanks

> 
>> ?
>>
>> Thanks
>>
>> On 17.12.2024 11:12, Arseniy Krasnov wrote:
>>> 'hci_register_dev()' calls power up function, which is executed by
>>> kworker - 'hci_power_on()'. This function does access to bluetooth chip
>>> using callbacks from 'hci_ldisc.c', for example 'hci_uart_send_frame()'.
>>> Now 'hci_uart_send_frame()' checks 'HCI_UART_PROTO_READY' bit set, and
>>> if not - it fails. Problem is that 'HCI_UART_PROTO_READY' is set after
>>> 'hci_register_dev()', and there is tiny chance that 'hci_power_on()' will
>>> be executed before setting this bit. In that case HCI init logic fails.
>>>
>>> Patch moves setting of 'HCI_UART_PROTO_READY' before calling function
>>> 'hci_uart_register_dev()'.
>>>
>>> Signed-off-by: Arseniy Krasnov <avkrasnov@...utedevices.com>
>>> ---
>>>  Changelog v1->v2:
>>>  * Move 'set_bit()' before 'hci_uart_register_dev()' instead of
>>>    adding new bit 'HCI_UART_PROTO_INIT'.
>>>
>>>  drivers/bluetooth/hci_ldisc.c | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
>>> index 30192bb083549..07b9aa09bbe2e 100644
>>> --- a/drivers/bluetooth/hci_ldisc.c
>>> +++ b/drivers/bluetooth/hci_ldisc.c
>>> @@ -704,12 +704,13 @@ static int hci_uart_set_proto(struct hci_uart *hu, int id)
>>>
>>>       hu->proto = p;
>>>
>>> +     set_bit(HCI_UART_PROTO_READY, &hu->flags);
>>> +
>>>       err = hci_uart_register_dev(hu);
>>>       if (err) {
>>>               return err;
>>>       }
>>>
>>> -     set_bit(HCI_UART_PROTO_READY, &hu->flags);
>>>       return 0;
>>>  }
>>>
> 
> 
>