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

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Message-ID: <CABBYNZKXJAvOQie37yCgNUTct2HXzPYNNqNN5Am+pGViGe1=Gw@mail.gmail.com>
Date: Thu, 19 Dec 2024 14:01:05 -0500
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: Arseniy Krasnov <avkrasnov@...utedevices.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

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.

> ?
>
> 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;
> >  }
> >



-- 
Luiz Augusto von Dentz