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


Some details about my test environment:
Hardware: Ti Sitara AM3357ZCZ with 128MiB memory
Kernel: vanilla 4.6

The relevant part of my .dts:
#include "am33xx.dtsi"

/ {
...
    cpus {
        cpu@0 {
            cpu0-supply = <&dcdc2_reg>;
            operating-points = <
                /* kHz    uV */
                800000  1300000
                600000  1112000
                300000   969000
            >;
        };
    };

    memory {
        device_type = "memory";
        reg = <0x80000000 0x08000000>; /* 128 Mib */
    };
...

    leds {
        pinctrl-names = "default";
        pinctrl-0 = <&user_leds_s0>;

        compatible = "gpio-leds";

...
        led2 {
            label = "2a_service_yellow";
            gpios = <&gpio1 2 GPIO_ACTIVE_HIGH>;
            linux,default-trigger = "2a_service_yellow";
            default-state = "off";
        };

...
    };
...
};

&am33xx_pinmux {
    pinctrl-names = "default";
    pinctrl-0 = <&gpio_misc_pins>;

...
    user_leds_s0: user_leds_s0 {
        pinctrl-single,pins = <
...
            0x24 (PIN_OUTPUT_PULLDOWN | MUX_MODE7) /* (T10)
gpmc_ad9.gpio0[23] */
        >;
    };
...
};
...

Kind regards
Daniel
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