Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933022AbcLBIs0 (ORCPT ); Fri, 2 Dec 2016 03:48:26 -0500 Received: from mail-wm0-f67.google.com ([74.125.82.67]:33273 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932820AbcLBIsW (ORCPT ); Fri, 2 Dec 2016 03:48:22 -0500 Date: Fri, 2 Dec 2016 09:48:18 +0100 From: Ralph Sennhauser To: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= Cc: Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, =?UTF-8?B?UmFm?= =?UTF-8?B?YcWCIE1pxYJlY2tp?= Subject: Re: [BUG 4.9] New led trigger usbport gets the kernel to panic Message-ID: <20161202094818.6b9c1ed2@gmail.com> In-Reply-To: References: <20161121094022.30478a37@gmail.com> <43ea90fb-780a-3612-77dd-265e877ac18e@milecki.pl> <20161201152825.3b2686db@gmail.com> Organization: none X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id uB28mYN7019280 Content-Length: 3422 Lines: 80 On Thu, 1 Dec 2016 17:56:07 +0100 Rafał Miłecki wrote: > On 12/01/2016 03:28 PM, Ralph Sennhauser wrote: > > Below the oops with your debug patch applied. > > > > (...) > > > > root@wrt1900acs:/# cd sys/class/leds/pca963x\:shelby\:white\:usb2/ > > root@wrt1900acs:/sys/devices/platform/soc/soc:internal-regs/f1011000.i2c/i2c-0/0-0068/leds/pca963x:shelby:white:usb2# > > echo usbport > trigger [ 124.727665] leds > > pca963x:shelby:white:usb2: [usbport_trig_add_port] port:dd708240 > > [ 124.735266] leds pca963x:shelby:white:usb2: > > [usbport_trig_add_port] port->port_name:usb1-port1 > > port->data:dd708140 [ 124.745671] leds pca963x:shelby:white:usb2: > > [usbport_trig_add_port] port:dd7083c0 [ 124.753194] leds > > pca963x:shelby:white:usb2: [usbport_trig_add_port] > > port->port_name:usb2-port1 port->data:dd708140 [ 124.763594] leds > > pca963x:shelby:white:usb2: [usbport_trig_add_port] port:dd708300 > > [ 124.771114] leds pca963x:shelby:white:usb2: > > [usbport_trig_add_port] port->port_name:usb3-port1 > > port->data:dd708140 > > root@wrt1900acs:/sys/devices/platform/soc/soc:internal-regs/f1011000.i2c/i2c-0/0-0068/leds/pca963x:shelby:white:usb2# > > echo 1 > ports/usb2-port1[ 171.649751] leds > > pca963x:shelby:white:usb2: [usbport_trig_port_store] buf:1 > > [ 171.649751] size:2 > > > > [ 171.660160] leds pca963x:shelby:white:usb2: > > [usbport_trig_port_store] port:dd7083c0 [ 171.668103] leds > > pca963x:shelby:white:usb2: [usbport_trig_port_store] > > port->port_name:usb2-port1 port->data:dd708140 [ 171.678678] > > [usbport_trig_update_count] usbport_data->count:0 [ 171.684457] > > [usbport_trig_update_count] usbport_data->count:0 [ 171.690253] > > Unable to handle kernel NULL pointer dereference at virtual address > > 00000000 > > Oh, so this happens a bit later than I expected or I could read from > the backtrace. Anyway this debugging was still helpful, I think I can > see a possible problem. > > So most likely the crash happens at the: > led_cdev->brightness_set(led_cdev, ...); > call. I'm not sure what I was thinking when writing that code. It > looks wrong. > > The thing is some LEDs (drivers) don't provide brightness_set op. > It's fine, we should just use brightness_set_blocking op when that > happens. Of course kernel has proper helpers for that, we don't have > to worry about the choice of op or scheduling the work. I have no > idea why I didn't use a proper helper in the first place. > > So we should simply replace above call with one of following ones: > 1) led_set_brightness(led_cdev, ...); > 2) led_set_brightness_nosleep(led_cdev, ...); > 3) led_set_brightness_sync(led_cdev, ...); > > I still have to check which one is correct. In theory we don't deal > blinking at this point so we shouldn't need to use led_set_brightness. > > led_set_brightness_nosleep looks like the most likely correct choice. > > led_set_brightness_sync requires brightness_set_blocking which is not > always present so most likely we don't want this one. > > > If you have some free time and you want to play with this, please > replace led_cdev->brightness_set > with > led_set_brightness_nosleep > and give it a try. This should fix crashes for you. > > I'll look at this again during next days. Hi Rafał I just gave 2) led_set_brightness_nosleep a try. The kernel no longer crashes and the led does work as expected. Thanks Ralph