perl-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Torsten Foertsch <torsten.foert...@gmx.net>
Subject Re: Releasing an independent Apache::SizeLimit to CPAN?
Date Fri, 16 Jun 2006 17:08:19 GMT
On Friday 16 June 2006 17:23, Perrin Harkins wrote:
> Dave Rolsky wrote:
> > Apache::SizeLimit has a long-standing bug on Linux where it never
> > actually kills a child, because of Perl's caching of ppid info
> > internally, and the way this interacts with Apache's forking.
> >
> > See this thread for details:
> > http://mail-archives.apache.org/mod_mbox/perl-modperl/200505.mbox/%3C51EE
> >FE1ECF72D811B384000E7F228BB7024CC6BC@DEBAGE71.BERTELSMANN.DE%3E
>
> You're saying that it always thinks it is in the main process even
> though it's actually in a child?  I haven't seen this behavior.  Is it
> specific to certain versions of Perl or Linux?

Yes, since 5.8.1. The problem is that the now old linux-threads implementation 
returns different values for getpid() and getppid() for different threads. 
Hence Perl decides better to cache these values and update the cache on 
fork() to make it more compatible with other thread implementations. Since 
Apache does its own fork the cache is not updated. Mp2 contains code that 
handles the situation but mp1 does not.

For more information see also

http://www.gossamer-threads.com/lists/perl/porters/193162
http://www.gossamer-threads.com/lists/perl/porters/175806

Dave, have you tried the proposed approach from the thread you mentioned?

> PerlModule Perl::AfterFork
> PerlModule Apache::Constants
> PerlInitHandler "sub {Perl::AfterFork::reinit(); return Apache::OK;}"
> 
> or
> 
> PerlModule Perl::AfterFork
> PerlInitHandler "sub {Perl::AfterFork::reinit();}"

If you are working on Apache::SizeLimit maybe you could incorporate also 
Linux::Smaps for newer kernels. Also the problem of counting out of core 
pages could be addressed at least in the docs, see

http://www.gossamer-threads.com/lists/modperl/dev/84375

Torsten

Mime
View raw message