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

[Daniel Gorsulowski]

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).

Kind regards,
Daniel