Messages in this thread | | | Subject | Re: [ISSUE] Memleak in LED sysfs on heavy usage | From | Jacek Anaszewski <> | Date | Fri, 16 Sep 2016 23:08:03 +0200 |
| |
On 09/16/2016 09:44 PM, Greg KH wrote: > On Fri, Sep 16, 2016 at 08:49:44PM +0200, Jacek Anaszewski wrote: >> On 09/16/2016 04:39 PM, Greg KH wrote: >>> On Fri, Sep 16, 2016 at 04:32:39PM +0200, Jacek Anaszewski wrote: >>>> 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. >>> >>> Why are you abusing uevents for flashing an LED? Please don't do that, >>> it's not what that interface is for at all. >> >> It is called in a result of setting brightness value to LED_OFF, >> which also removes registered trigger if any. > > So every time the LED goes off a uevent happens? That's not a good > design.
We had a bug, but it was fixed with recent commit. Now the uevent will happen when LED goes off only if trigger has been set.
>> The rationale for calling kobject_uevent_env() is given in the >> relevant commit message: >> >> commit 52c47742f79d9240f90af9a6722fe8bb3fa8c0f9 >> Author: Colin Cross <ccross@android.com> >> Date: Mon Aug 27 09:31:49 2012 +0800 >> >> leds: triggers: send uevent when changing triggers >> >> Some triggers create sysfs files when they are enabled. Send a uevent >> "change" notification whenever the trigger is changed to allow userspace >> processes such as udev to modify permissions on the new files. >> >> A change notification will also be sent during registration of led class >> devices or led triggers if the default trigger of an led class device >> is found. > > If a sysfs file is removed, then I could see a change event being ok. > But that's not what this patch does, it ALWAYS sends a uevent, even if > nothing changed!
Yes, the function needs to be fixed. I'll submit relevant patch soon.
> Please fix that, otherwise you are going to really annoy userspace tools > with this. > > But even then, I don't see how the uevent code has a memory leak with > this, do you?
Not at the moment, but the fact is that the issue ceases to occur after commenting the line out.
> And why aren't you checking the return value of > kobject_uevent_env()?
Will fix.
-- Best regards, Jacek Anaszewski
| |