Bug #2349: fork() after signal(SIGCHLD, SIG_IGN) produces zombies - DragonFlyBSD - DragonFlyBSD bugtracker

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Bug #2349

closed

fork() after signal(SIGCHLD, SIG_IGN) produces zombies

Added by matthiasr over 12 years ago. Updated about 12 years ago.

Status:

Closed

Priority:

Normal

Assignee:

Category:

Target version:

Start date:

04/17/2012

Due date:

% Done:

100%

Estimated time:

Description

The code in the attached zombifier.c makes every exiting child into a zombie on master¹. This doesn't happen on any non-DragonFly system I could test it on, and from what I gather from this discussion² and what Wikipedia says about SUSv3/POSIX-1.2001 the correct behaviour is not to keep them around if the SIGCHLD handler is explicitly set to SIG_IGN.

This has realworldly bitten me because the FCGI-to-CGI-wrapper I use⁴ relies on this behaviour and I couldn't SSH into my server as a non-root user due to PID exhaustion.

[1] DragonFly zz.2pktfkt.net 3.1-DEVELOPMENT DragonFly v3.1.0.545.g4c42b-DEVELOPMENT #6: Tue Apr 17 21:24:31 CEST 2012 matthias@zz.2pktfkt.net:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64
[2] http://markmail.org/message/3s4jj7dpgw34yvmh
[3] http://en.wikipedia.org/wiki/Zombie_process
[4] http://pkgsrc.se/wip/fcgiwrap

Files

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zombifier.c (401 Bytes) zombifier.c	test case – run and check "ps axl \| fgrep zombifier"	matthiasr, 04/17/2012 01:11 PM
dragonfly-SIGCHLD.patch (2.84 KB) dragonfly-SIGCHLD.patch	proposed patch	matthiasr, 04/17/2012 02:42 PM

Related issues 1 (0 open — 1 closed)

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Updated by herrgard over 12 years ago

On Tue, Apr 17, 2012 at 01:11:09PM -0700, Matthias Rampke via Redmine wrote:

The code in the attached zombifier.c makes every exiting child into a zombie on master¹. This doesn't happen on any non-DragonFly system I could test it on, and from what I gather from this discussion² and what Wikipedia says about SUSv3/POSIX-1.2001 the correct behaviour is not to keep them around if the SIGCHLD handler is explicitly set to SIG_IGN.

This has realworldly bitten me because the FCGI-to-CGI-wrapper I use⁴ relies on this behaviour and I couldn't SSH into my server as a non-root user due to PID exhaustion.

Hm, maybe this could be the same reason why I keep getting zombies with firefox, thunderbird and xpdf all the time.

Max

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Updated by matthiasr over 12 years ago

File dragonfly-SIGCHLD.patch dragonfly-SIGCHLD.patch added
% Done changed from 0 to 50

Here's a patch against master I cargoculted from FreeBSD-current, taking the patches in that old thread as pointers. The kernel boots and works for me and the test case no longer generates zombie processes.

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