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From "Ryan Bloom" <...@covalent.net>
Subject RE: how to debug worker mpm httpd with gdb?
Date Tue, 12 Mar 2002 23:06:13 GMT
> On Tue, Mar 12, 2002 at 06:21:27PM +0800, Stas Bekman wrote:
> > Any guidelines for debugging threaded (worker) mpm? I've read the
> > relevant gdb section, but it isn't enough. I couldn't find any
relevant
> > info in httpd-docs-2.0/manual/developer.
> >
> > I'm interested in tips making the debug process easier. Does anybody
> > have a cheatlist with useful tips/notes and willing to share it?
> <snip, snip>
> > During the first request yet another thread starts. And one of the
old
> > ones goes away.
> >
> > It seems that the newest thread is the one I need to attach to. But
when
> > I attach to it once, in a while I get switched to the previous
thread,
> > etc. This is very confusing and non-productive :(
> 
> Yeah, well, I've maintained that worker doesn't have the right
> support for debugging.  Nobody else seems to agree with me.  =(
> 
> AIUI (without placing words in anyone's mouth), it is that if you
> are using -X on worker, you want to debug the MPM *not* Apache.
> So, if you want to reliably test your code (i.e. a module), you
> should use the prefork MPM.  If you are using worker, you need to
> attach to the "right" worker thread and hope you get the right
> thread.  I've complained to the appropriate parties and they
> maintain their position is correct.  Whatever.  Feel free to
> join the complaint line.  Worker is useless in -X mode.

How would you fix this?  By having the worker MPM go into a single
threaded, single process mode with -X?  That won't actually solve the
problem, because the OS will still create the manager thread.  This is
just part of the pain of doing threaded debugging on Unix.

Ryan



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