On Sun, Mar 18, 2018 at 10:51:33PM +0800, Jia-Ju Bai wrote:
> line6_read_data() is never called in atomic context.
>
> The call chains ending up at line6_read_data() are:
> [1] line6_read_data() <- line6_read_serial_number() -> pod_startup4()
> [2] line6_read_data() <- line6_read_serial_number() <-
> podhd_startup_workqueue()
> [3] line6_read_data() <- podhd_dev_start() <- podhd_startup_workqueue()
> [4] line6_read_data() <- line6_read_serial_number() <- toneport_init()
> <- line6_probe()
> [5] line6_read_data() <- toneport_init() <- line6_probe()
>
> pod_startup4() and podhd_startup_workqueue() are set in INIT_WORK().
> line6_probe() is called in toneport_probe(), pod_probe(), podhd_probe()
> and variax_probe(), which are set as ".probe" in usb_driver structure.
> These functions are not called in atomic context.
>
> Despite never getting called from atomic context, line6_read_data()
> calls mdelay for busy wait.
> That is not necessary and can be replaced with msleep to
> avoid busy waiting.
Can we have usleep_range here? Please see Documentation/timers/timers-howto.txt
for rationale and range settings.
> This is found by a static analysis tool named DCNS written by myself.
Here I'm assuming you do not have hardware and do not know how it works,
therefore few more people from 'git log --follow sound/usb/line6/driver.c'
were added to Cc list. Hopefully they can clarify the right range value.
Thank you.
> Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
> ---
> sound/usb/line6/driver.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
> index 0ff5a7d..af99e73 100644
> --- a/sound/usb/line6/driver.c
> +++ b/sound/usb/line6/driver.c
> @@ -356,7 +356,7 @@ int line6_read_data(struct usb_line6 *line6, unsigned address, void *data,
>
> /* Wait for data length. We'll get 0xff until length arrives. */
> for (count = 0; count < LINE6_READ_WRITE_MAX_RETRIES; count++) {
> - mdelay(LINE6_READ_WRITE_STATUS_DELAY);
> + msleep(LINE6_READ_WRITE_STATUS_DELAY);
>
> ret = usb_control_msg(usbdev, usb_rcvctrlpipe(usbdev, 0), 0x67,
> USB_TYPE_VENDOR | USB_RECIP_DEVICE |
> --
> 1.9.1
>
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