From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [ISSUE] Memleak in LED sysfs on heavy usage Date: Fri, 16 Sep 2016 20:49:44 +0200 Message-ID: <6f9326ea-0ff6-7ff7-58d5-210d0c3e7252@gmail.com> References: <37b949b3-6a9a-b8e3-c164-5ac2d44c9b3c@samsung.com> <4d51014d-c8fa-4687-cae8-1a8dd0f79beb@samsung.com> <7bb9a00e-0927-2fdc-5733-64bf922ebed6@samsung.com> <20160916140626.GB391@kroah.com> <20160916143951.GA20908@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wm0-f67.google.com ([74.125.82.67]:33253 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935345AbcIPSuX (ORCPT ); Fri, 16 Sep 2016 14:50:23 -0400 In-Reply-To: <20160916143951.GA20908@kroah.com> Sender: linux-leds-owner@vger.kernel.org List-Id: linux-leds@vger.kernel.org To: Greg KH , Jacek Anaszewski Cc: Daniel Gorsulowski , "linux-leds@vger.kernel.org" , "linux-kernel@vger.kernel.org" On 09/16/2016 04:39 PM, Greg KH wrote: > On Fri, Sep 16, 2016 at 04:32:39PM +0200, Jacek Anaszewski wrote: >> On 09/16/2016 04:06 PM, Greg KH wrote: >>> On Fri, Sep 16, 2016 at 03:41:09PM +0200, Jacek Anaszewski wrote: >>>> On 09/16/2016 02:08 PM, Daniel Gorsulowski wrote: >>>>> Hi Jacek, >>>>> >>>>> Am 16.09.2016 um 13:25 schrieb Jacek Anaszewski: >>>>>> On 09/16/2016 10:15 AM, Daniel Gorsulowski wrote: >>>>>>> Hi Jacek, >>>>>>> >>>>>>> Am 16.09.2016 um 09:31 schrieb Jacek Anaszewski: >>>>>>>> Hi Daniel, >>>>>>>> >>>>>>>> On 09/12/2016 10:50 AM, Daniel Gorsulowski wrote: >>>>>>>>> Hello! >>>>>>>>> >>>>>>>>> Please consider if I made something wrong, sending this issue. This is >>>>>>>>> my first contact to the LKML. >>>>>>>>> By mistake, I accessed an LED via /sys/class/leds subsystem very >>>>>>>>> fast in >>>>>>>>> an user application. I figured out, that the free user memory >>>>>>>>> decreased >>>>>>>>> constantly. So I tried to analyze the Problem and wrote a litte >>>>>>>>> script: >>>>>>>>> >>>>>>>>> #!/bin/sh >>>>>>>>> while [ 1 ]; do >>>>>>>>> echo 1 > /sys/class/leds/2a_service_yellow/brightness >>>>>>>>> echo 0 > /sys/class/leds/2a_service_yellow/brightness >>>>>>>>> done >>>>>>>>> >>>>>>>>> And voila, I was able to reproduce the problem. >>>>>>>>> So I add a bit more debugging: >>>>>>>>> >>>>>>>>> #!/bin/sh >>>>>>>>> cnt=0 >>>>>>>>> while [ 1 ]; do >>>>>>>>> if [ `expr $cnt % 1000` -eq 0 ]; then >>>>>>>>> free | grep Mem: | cut -d' ' -f25 >>>>>>>>> fi >>>>>>>>> echo 1 > /sys/class/leds/2a_service_yellow/brightness >>>>>>>>> echo 0 > /sys/class/leds/2a_service_yellow/brightness >>>>>>>>> let "cnt++" >>>>>>>>> done >>>>>>>>> >>>>>>>>> And huh? No memory is eaten anymore. So it looks like, the problem >>>>>>>>> only >>>>>>>>> occours on heavy (fast) usage of /sys/class/leds subsystem. >>>>>>>>> >>>>>>>>> I rewrote the script and toggled a GPIO pin, but there was no problem >>>>>>>>> recognizable. >>>>>>>> >>>>>>>> I've been unable to reproduce the problem with leds-aat1290 driver >>>>>>>> and Samsung M0 board. It must be driver specific issue. >>>>>>>> What driver did you use? >>>>>>>> >>>>>>> I defined LEDS_GPIO and so I'm using leds-gpio driver. >>>>>>> danielg@debby:~/opt/prj/ti-linux-kernel$ cat .config | grep LEDS | grep >>>>>>> -v "^# " >>>>>>> CONFIG_INPUT_LEDS=y >>>>>>> CONFIG_NEW_LEDS=y >>>>>>> CONFIG_LEDS_CLASS=y >>>>>>> CONFIG_LEDS_GPIO=y >>>>>>> CONFIG_LEDS_TRIGGERS=y >>>>>>> CONFIG_LEDS_TRIGGER_TIMER=y >>>>>>> CONFIG_LEDS_TRIGGER_ONESHOT=y >>>>>>> CONFIG_LEDS_TRIGGER_HEARTBEAT=y >>>>>>> CONFIG_LEDS_TRIGGER_GPIO=y >>>>>>> CONFIG_LEDS_TRIGGER_DEFAULT_ON=y >>>>>>> CONFIG_LEDS_TRIGGER_TRANSIENT=y >>>>>>> >>>>>> >>>>>> Unfortunately I am still unable to reproduce the problem with leds-gpio. >>>>>> I'm not observing any heavy usage with your test case: >>>>>> >>>>>> ~#free >>>>>> total used free shared buffers >>>>>> cached >>>>>> Mem: 1028092 61364 966728 0 8416 22396 >>>>>> -/+ buffers/cache: 30552 997540 >>>>>> Swap: 0 0 0 >>>>>> >>>>>> >>>>>> Actually you didn't give any numbers. What kernel version are you using? >>>>>> >>>>> As I wrote, the problems occurred in vanilla 4.6 kernel, but also in 4.4 >>>>> kernel (with PREEMPT-RT Patchset). >>>> >>>> Heh, funny coincidence. I was testing this on recent linux-leds.git, >>>> for-next branch and was not able to detect the issue. It started to >>>> appear after resetting HEAD to 4.8-rc2 base. Finally it turned out >>>> that what fixes the issue is the most recent commit [1]. >>>> >>>> Further investigation revealed that this is kobject_uevent_env(), >>>> called from led_trigger_set(), which causes memory leaks when called >>>> with high frequency. >>> >>> Really? Where in kobject_uevent_env() is the memory leak? >> >> I'll chase it down when and will let you know. This may be >> non-trivial issue as it suffices to add "sleep 0.1" between >> brightness setting operations to prevent it. > > Why are you abusing uevents for flashing an LED? Please don't do that, > it's not what that interface is for at all. It is called in a result of setting brightness value to LED_OFF, which also removes registered trigger if any. The rationale for calling kobject_uevent_env() is given in the relevant commit message: commit 52c47742f79d9240f90af9a6722fe8bb3fa8c0f9 Author: Colin Cross Date: Mon Aug 27 09:31:49 2012 +0800 leds: triggers: send uevent when changing triggers Some triggers create sysfs files when they are enabled. Send a uevent "change" notification whenever the trigger is changed to allow userspace processes such as udev to modify permissions on the new files. A change notification will also be sent during registration of led class devices or led triggers if the default trigger of an led class device is found. -- Best regards, Jacek Anaszewski