Bug#926896: sysvinit-utils: pidof is unreliable

[Hoyer, David]

We have also been experiencing this problem since moving to Buster.   We never saw this with Jessie.   I believe it comes down to the following code in readproc:

                        if ( (strchr(process_status, 'D') != NULL) ||
                             (strchr(process_status, 'Z') != NULL) ){
                           /* Ignore zombie processes or processes in
                              disk sleep, as attempts
                              to access the stats of these will
                              sometimes fail. */
                              if (p->argv0) free(p->argv0);
                              if (p->argv1) free(p->argv1);
                              if (p->statname) free(p->statname);
                             free(p);
                             continue;
                        }

Our scenario is similar although not with the same process that is described below.    It seems like this makes pidof not as effective for finding the pid of a process if D states are skipped.   Are there alternatives to pidof?   (BTW the -z option does not appear to help since this code snippet will remove it from the process list).

-----Original Message-----
From: Thorsten Glaser <t.glaser at tarent.de> 
Sent: Tuesday, October 22, 2019 6:26 PM
To: jsmith at resonatingmedia.com; 926896 at bugs.debian.org
Subject: Bug#926896: sysvinit-utils: pidof is unreliable

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On Tue, 22 Oct 2019, Jesse Smith wrote:

> >    any ideas how it could be possible for process to be discovered by
> >    ps(1), but not pidof(1)?

> I can think of a few possibilities, though they seem unlikely. One is 
> that the process could be crashing and restarting, making it a zombie

or in D state, doing disc I/O… more likely even.

> for brief periods of time. Testing pidof with the "-z" flag would fill 
> in the "holes" in the test output if that theory is correct.

Also: start-stop-daemon --status should probably be used ipv pidof.

(Even its manpage says so.)

bye,
//mirabilos
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