linux-kernel - Re: [ISSUE] Memleak in LED sysfs on heavy usage

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Date:   Fri, 16 Sep 2016 14:08:34 +0200
From:   Daniel Gorsulowski <daniel.gorsulowski@....eu>
To:     Jacek Anaszewski <j.anaszewski@...sung.com>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [ISSUE] Memleak in LED sysfs on heavy usage

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 $cnt % 1000` -eq 0 ]; then
>>>>                 free | grep Mem: | cut -d' ' -f25
>>>>         fi
>>>>         echo 1 > /sys/class/leds/2a_service_yellow/brightness
>>>>         echo 0 > /sys/class/leds/2a_service_yellow/brightness
>>>>         let "cnt++"
>>>> done
>>>>
>>>> And huh? No memory is eaten anymore. So it looks like, the problem only
>>>> occours on heavy (fast) usage of /sys/class/leds subsystem.
>>>>
>>>> I rewrote the script and toggled a GPIO pin, but there was no problem
>>>> recognizable.
>>>
>>> I've been unable to reproduce the problem with leds-aat1290 driver
>>> and Samsung M0 board. It must be driver specific issue.
>>> What driver did you use?
>>>
>> I defined LEDS_GPIO and so I'm using leds-gpio driver.
>> danielg@...by:~/opt/prj/ti-linux-kernel$ 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).

Kind regards,
Daniel