Return-path: Received: from sonata.ens-lyon.org ([140.77.166.138]:33698 "EHLO sonata.ens-lyon.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752536AbaIVHpq (ORCPT ); Mon, 22 Sep 2014 03:45:46 -0400 Date: Mon, 22 Sep 2014 09:37:26 +0200 From: Samuel Thibault To: Kari Suvanto Cc: "Hugh Dickins Sabrina Dubroca" , Valdis.Kletnieks@vt.edu, Vincent Donnefort , Bryan Wu , linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org Subject: Re: 3.17-rc1: leds blink workqueue causes sleeping BUGs Message-ID: <20140922073726.GQ3349@type.wlan.youpi.perso.aquilenet.fr> (sfid-20140922_094602_946869_9354522C) References: <541FD018.107@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <541FD018.107@gmail.com> Sender: linux-wireless-owner@vger.kernel.org List-ID: Kari Suvanto, le Mon 22 Sep 2014 10:30:32 +0300, a ?crit : > >Ew. I'll have a look. > > Any update on this one? I have already sent it, yes, on Tue, 26 Aug 2014 11:17:25 +0200, here it is again. Samuel Subject: [PATCHv2][input-led] Defer input led work to workqueue When the kbd changes its led state (e.g. caps lock), this triggers (led_trigger_event) the kbd-capsl trigger, which is by default used by the vt::capsl LED, which triggers (led_trigger_event) the vt-capsl trigger. These two nested led_trigger_event calls take a trig->leddev_list_lock lock and thus lockdep complains. Actually the user can make the vt::capsl LED use its own vt-capsl trigger and thus build a loop. This produces an immediate oops. This changeset defers the second led_trigger_event call into a workqueue, which avoids the nested locking altogether. This does not prevent the user from shooting himself in the foot by creating a vt::capsl <-> vt-capsl loop, but the only consequence is the workqueue threads eating some CPU until the user breaks the loop, which is not too bad. Signed-off-by: Samuel Thibault --- Difference with v1: uses schedule_work instead of its own workqueue. --- a/drivers/input/leds.c +++ b/drivers/input/leds.c @@ -100,13 +100,24 @@ static unsigned long vt_led_registered[B /* Number of input devices having each LED */ static int vt_led_references[LED_CNT]; +static int vt_led_state[LED_CNT]; +static struct work_struct vt_led_work[LED_CNT]; + +static void vt_led_cb(struct work_struct *work) +{ + int led = work - vt_led_work; + + led_trigger_event(&vt_led_triggers[led], vt_led_state[led]); +} + /* VT LED state change, tell the VT trigger. */ static void vt_led_set(struct led_classdev *cdev, enum led_brightness brightness) { int led = cdev - vt_leds; - led_trigger_event(&vt_led_triggers[led], !!brightness); + vt_led_state[led] = !!brightness; + schedule_work(&vt_led_work[led]); } /* LED state change for some keyboard, notify that keyboard. */ @@ -244,6 +255,22 @@ void input_led_disconnect(struct input_d mutex_unlock(&vt_led_registered_lock); } +static int __init input_led_init(void) +{ + unsigned i; + + for (i = 0; i < LED_CNT; i++) + INIT_WORK(&vt_led_work[i], vt_led_cb); + + return 0; +} + +static void __exit input_led_exit(void) +{ +} + MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("User LED support for input layer"); MODULE_AUTHOR("Samuel Thibault "); +module_init(input_led_init); +module_exit(input_led_exit);