Re: [LTP] [v2 2/2] lib/tst_pid.c: Increase PIDS_RESERVED to avoid fork failure.

Cyril Hrubis
2023-02-14T14:24:51Z

Hi!
> > > > After Adjusting how we count used pid, we increase
> > > > the number of PIDS_RESERVED to void fork failure.
> > > nit: in this case I'd actually keep changes in single commit
> > > (otherwise first commit alone would break tests),
> >
> > Do we get a different result from ps and parsing /proc? That sounds
> > strange...
>
> I think that's because "ps -eT" would list threads with the same PID
> but with different SPID.
>
> I get the following output on my VM.
>
> ycliang@ubuntu01:~$ ps -eT | wc -l
> 170
> ycliang@ubuntu01:~$ ls -d /proc/[0-9]* | xargs -n1 | wc -l
> 127

Adjusting the RESERVED constant is then a lousy workaround that wouldn't
work for systems with many threads per process.

One alternative would be to open /proc/$PID/status and read the number
of threads from there. Should be as easy as one call to
SAFE_FILE_LINES_SCANF().

--
Cyril Hrubis
chrubis@suse.cz