From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754018AbeCRPXy (ORCPT ); Sun, 18 Mar 2018 11:23:54 -0400 Received: from eddie.linux-mips.org ([148.251.95.138]:53128 "EHLO cvs.linux-mips.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751539AbeCRPXx (ORCPT ); Sun, 18 Mar 2018 11:23:53 -0400 Date: Sun, 18 Mar 2018 16:23:49 +0100 From: Ladislav Michl To: Jia-Ju Bai Cc: perex@perex.cz, tiwai@suse.com, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, Markus Grabner , Stefan Hajnoczi , Chris Rorvick , Andrej Krutak Subject: Re: [alsa-devel] [PATCH 1/3] sound: usb: line6: Replace mdelay with msleep in line6_read_data Message-ID: <20180318152349.GA16414@lenoch> References: <1521384693-23336-1-git-send-email-baijiaju1990@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1521384693-23336-1-git-send-email-baijiaju1990@gmail.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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 > > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@alsa-project.org > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel