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

[Ilya Matveychikov]

> On Mar 3, 2020, at 3:43 PM, Josef Moellers <jmoellers at suse.de> wrote:
> 
> 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?

I hope I do pclose() all of them. Anyway, the same behavior I’m getting
with trying to do system(“ls -al / >/xxx”) before any popen(), just in
the beginning of the program. It fails! 

> 
> Josef
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