Date: Wed, 6 Sep 2000 13:36:53 -0700 (PDT) From: Mikko Tyolajarvi <mikko@dynas.se> To: Cy.Schubert@uumail.gov.bc.ca Cc: freebsd-stable@freebsd.org Subject: Re: running lyris for linux makes many zombies Message-ID: <200009062036.NAA19883@explorer.rsa.com> References: Your message of "Wed, 06 Sep 2000 13:03:14 EDT." <14774.30930.120103.685216@onceler.kciLink.com> <200009061756.e86Huaa75647@cwsys.cwsent.com>
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In local.freebsd-stable you write:
>In message <14774.30930.120103.685216@onceler.kciLink.com>, Vivek Khera
>writes:
>> On a FreeBSD 4.1-S cvsup'd yesterday, I'm running Lyris 4.0 for linux
>> (with the security patches installed). I had been running this on a
>> RedHat 6.0 system quite well, but I'd rather rid myself of that system
>> ;-)
>>
>> Anyhow, I'm getting *lots* of zombie processes being left around after
>> processing a few messages, and the number keeps growing. This did not
>> happen on the "real" linux system.
>>
>> Is there some knob I can turn on in the linux compatibility system to
>> get the zombies to be reaped properly? I have COMPAT_LINUX defined in
>> my kernel so the linux compat is statically linked into the kernel.
>Lyris is failing to issue a wait(2) call to obtain the exit status of
>children that have terminated. The kernel will keep a a process table
>entry for the terminated child until the exit status has been fetched
>by its parent.
>My guess the reason Linux doesn't have any zombies is that the Linux
>init(8) is getting involved to fetch the status and clean up after the
>application. This is not standard UNIX. What FreeBSD is doing, e.g.
>nothing as it's an application issue, is the correct thing to do.
>IIRC, there are some differences between SYSV and BSD in this regard,
>though I cannot remember the details and I don't have Stevens' book
>here to reference.
On SYSV (and Linux) doing "signal(SIGCHLD, SIG_IGN)" is sufficient to
get rid of zombies. On BSD, you have to use sigaction() with the
SA_NOCLDWAIT flag to get the same result.
(Two minutes later)
Yes, the following Q&D program does not leave a zombie child on linux.
But when the linux-compiled binary is run under the linuxulator, it
does leave a zombie.
I.e. linuxulator bug.
#include <signal.h>
int
main()
{
int pid;
signal(SIGCHLD, SIG_IGN);
if ((pid = (int)fork()) == 0) {
exit(0);
}
printf("Child is %d, go look for it!\n", pid);
sleep(30);
}
The same source compiled under FreeBSD also leaves a zombie, but that
is an entirely different matter (it is supposed to).
$.02,
/Mikko
--
Mikko Työläjärvi_______________________________________mikko@rsasecurity.com
RSA Security
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