TProcess.Execute/Terminate with root privileges for child process
lazarus / 32-Linux

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sporer@sctn.de · 2019-06-17 12:55

I'am launching an external process on a Raspberry PI (debian jessie)
with TProcess.
This external process is attempting to set it's own priority via the
Linux scheduler to a value of 80.
When I configure it in TProcess.CommandLine without "sudo"
(/home/pi/ext_process) the scheduler refuses to increase the PR value;
I can execute the external process with PR=20 and terminate it at any
time, as it is supposed to be.
On the other side, when I configure the CommandLine with "sudo" (sudo
/home/pi/ext_process) the scheduler increases the priority to 80, but
then I cannot terminate it any more (TProcess.Terminate).
And this is even the case, when I start the parent process (sudo
/home/pi/parent) with root privileges.
Does anyone have an idea how to resolve this?

Thanks in advance

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marcov · 2019-06-17 13:08

It doesn't make sense that an ordinary user would be able to terminate
root processes. So without special software like a special sudo this
is hard, and beyond the ability of normal compilers.

You need kernel cooperation for that.

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bylaardt · 2019-06-17 13:11

Quote from: sporer@sctn.de on June 17, 2019, 02:55:18 pmDoes anyone
have an idea how to resolve this?
Run your application as root

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sporer@sctn.de · 2019-06-17 13:17

by bylaardt: Run your application as root

Yes I was also trying this. The result is the same.

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sporer@sctn.de · 2019-06-17 13:52

Quote from: marcov on June 17, 2019, 03:08:01 pmIt doesn't make sense
that an ordinary user would be able to terminate root processes. So
without special software like a special sudo this is hard, and beyond
the ability of normal compilers.

You need kernel cooperation for that.

Ok, understood.
I will just manage with PR=20. Obviously there is no perceptible
difference (latency) with PR=20.
(The external process is streaming VoIP, the application is performing
the signalling protocol that controls the RTP stream)