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

[Daniel Gorsulowski <daniel.gorsulowski@esd.eu>]

Hi Jacek,

Am 16.09.2016 um 15:41 schrieb Jacek Anaszewski:
> 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.
>
> CC GregKH.
>
> [1]
> https://git.kernel.org/cgit/linux/kernel/git/j.anaszewski/linux-leds.git/commit/?h=for-next&id=f3f624941be0fafb29fff5c1411fa433feca792c
>
Nice to hear about the Fix, thanks for your investigation!

Kind regards,
Daniel