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

[Josef Moellers]

On 03.03.20 12:26, Ilya Matveychikov wrote:
> 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?
Just a shot in the dark: do you pclose() all popen()s?

Josef
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