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.

--
Best regards,
Jacek Anaszewski

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