linux-kernel - Re: [PATCH] bluetooth: hci_ll: Replace mdelay with msleep in download

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Date:   Wed, 7 Feb 2018 09:55:46 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     "Gustavo F. Padovan" <gustavo@...ovan.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bluetooth: hci_ll: Replace mdelay with msleep in
 download_firmware

Hi Jia-Ju,

> download_firmware() is never called from atomic context.
> 
> It is only called by ll_setup() that is called only via function pointer 
> "->setup" used in hci_uart_setup() in drivers/bluetooth/hci_serdev.c and
> drivers/bluetooth/hci_ldisc.c. hci_uart_setup() is called only 
> via function pointer "->setup" used in hci_dev_do_open() 
> in net/bluetooth/hci_core.c.
> All of the above functions do not enter atomic context.
> 
> Besides, ll_setup() calls msleep() and hci_dev_do_open calls mutex_lock().
> So it indicates that all the above functions call functions that can sleep.
> 
> Despite never getting called from atomic context, download_firmware() 
> calls mdelay() for busy wait.
> That is not necessary and can be replaced with msleep to avoid busy wait.
> 
> This is found by a static analysis tool named DCNS written by myself.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
> ---
> drivers/bluetooth/hci_ll.c |    2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel