[M3devel] cvsup

[Jay K]

Dragisha, Really? The server? With the -C flag and/or -f?

 

Evidence is very very very very very good as to what is going on here.

  It is all related to "fork1" vs. "forkall".

  fork1 is the overwhelming usual behavior (Solaris has an option),

  and basically *any* library that uses pthreads is obligated to use

   pthread_atfork, be it a C library or the Modula-3 library, etc..

 

   The application cannot do things, unless

   the library exposes its internal locks. The Posix spec for

   pthread_atfork explains the problem.

 

  Consider C code that links in Modula-3 code.

  C code is fairly free to use the fork + do work model. It isn't very common,

   but it does exist, and people have gone to extra length to keep it viable.

   bash and ccache I believe both use this model.

 

 

Granted, if you had your own kernel thread implementation, it might

have addressed this.

 

 

I have a version now that has served over 1000 requests, similar to what I sent, but a bit reduced. The main change was I just called pthread_mutex_lock/unlock over the locks in ThreadPThread.m3, instead of using SuspendOthers. Haven't tested on Solaris/Darwin yet, just Linux. This version also doesn't expose the ForkProcessAndAllThreads functions.

The client has to restart its threads, or in the cvsupd case, don't depend on the dispatcher thread to survive fork.

I want to still try out the "bigger" change, but with the simpler lock/unlock.

And test on Solaris and Darwin.

 

 

I think for SuspendOthers to not work is not surprising.

The threads can still hold a few locks even if suspended, I'm pretty sure.

The point is to fork in a "controlled" fashion -- all locks held, and in

the right order, so that both parent and child can release them.

 

 

Taking "all" the locks in Prepare is more reliable.

 

 

I do wonder if really "all" locks need to be taken.

I only take the static ones declared in PThreadThread.c.

 

 - Jay

 
> Subject: Re: [M3devel] cvsup
> From: dragisha at m3w.org
> To: jay.krell at cornell.edu
> CC: hosking at cs.purdue.edu; m3devel at elegosoft.com
> Date: Wed, 17 Mar 2010 13:29:43 +0100
> 
> Yes, I can. I am building it regularly, from version to version, at
> least few times a year. And it also worked with my ancient kernel thread
> implementation. Was one of stress tests.
> 
> On Tue, 2010-03-16 at 16:10 +0000, Jay K wrote:
> > 
> > (Can anyone claim to have seen cvsup server work with kernel threads?)
> -- 
> Dragiša Durić <dragisha at m3w.org>
> 
 		 	   		  
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