[systemd-devel] UDEV popen/system returns error if called from the program (RUN option)

[Ilya Matveychikov]

Dear Lennart,

Thank you for the reply.

> On Mar 3, 2020, at 12:54 PM, Lennart Poettering <lennart at poettering.net> wrote:
> 
> On Mo, 02.03.20 00:35, Ilya Matveychikov (matvejchikov at gmail.com) wrote:
> 
>> Hey guys,
>> 
>> I’m not sure is it the right place to ask about the UDEV or not.
>> 
>> Anyways, I have a problem with running custom program from the UDEV rule (RUN+= option).
>> The problem is somehow related to fork/exec, I can’t tell for sure.
>> 
>> My code (this custom “RUN+=“-binary) using popen() to call external program
>> and get the result using stream. Once I run this custom program alone it works
>> perfectly well. But once it is executed under the systemd/udev via the rule
>> this popen() returns error with the code ENOMEM which is very strange for me
>> as the system has like 32Gb of RAM.
>> 
>> The same happen with system() ...
>> 
>> Do you guys have any glue of what the heck is going on?
>> Are there any constraints on what can be done in “programs”?
> 
> We enforce a limit on the number of processes/threads forked off
> services, and udevd has a limt set like that too, via the TasksMax=
> setting in its unit file. Maybe you are leaking processes/threads
> somehow and hit that limit?

I don’t do any multithreading in my program, except some popen()’s ..

My system (archlinux) has "TasksMax=infinity” line in file:
/usr/lib/systemd/system/sysinit.target.wants/systemd-udev.service

Any other tips?


> 
> Lennart
> 
> --
> Lennart Poettering, Berlin