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

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Date:   Fri, 16 Sep 2016 13:25:07 +0200
From:   Jacek Anaszewski <j.anaszewski@...sung.com>
To:     Daniel Gorsulowski <daniel.gorsulowski@....eu>,
        "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

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?

-- 
Best regards,
Jacek Anaszewski