[M3commit] CVS Update: cm3

[Tony Hosking]

We've been over this before.  The run-time libraries (including sysutils) can be assumed to bootstrap from a *new* compiler, which has itself been compiled against the *old* libraries.  Then, you can build a *new new* compiler linked against the *new* libraries.  Let's not make the libraries have braindead code when it is not necessary.  They should be kept clean going forward!

On 10 Feb 2010, at 12:00, Jay K wrote:

> sysutils has somewhat of a need to know if it is using user threads.
> We've been over this multiple times through the years.
> Never seems to be 100% resolved, but a solid 99%.
>  
>  
> It runs a process and waits.
> Historically in sysutils and m3core this was sleep/wait(nohang) in a loop.
> It was identified by people as a major performance problem.
>  Because the process exits fairly quickly but you have to wait for the sleep to finish.
>  Sleep being Modula-3 Thread.Sleep I guess -- call into the user thread scheduler.
> By and by, most platforms got kernel threads. Changing it to be wait(hang)
> became good, faster, no deadlock. But openbsd comes along with lame
> pthreads, usermode at that, so we use user threads, and wait(hang)
> could deadlock..
>  
>  
> There is an interface in m3core to handle this stuff, but if
> you bootstrap from an old build, it isn't there.
>  
>  
> Mitigating factor as I understand that we don't use threads agressively,
> so the deadlock isn't actually likely.
> "we" meaning code that launches processes.
>  
>  
> I understand that ideally you don't care if you are using userthreads or kernelthreads.
> But the abstraction historically was incomplete.
>  
>  
>  - Jay
> 
>  
> > From: hosking at cs.purdue.edu
> > Date: Wed, 10 Feb 2010 10:16:24 -0500
> > To: jkrell at elego.de
> > CC: m3commit at elegosoft.com
> > Subject: Re: [M3commit] CVS Update: cm3
> > 
> > Huh? Cryptic comment.
> > 
> > On 10 Feb 2010, at 12:20, Jay Krell wrote:
> > 
> > > CVSROOT: /usr/cvs
> > > Changes by: jkrell at birch. 10/02/10 12:20:55
> > > 
> > > Modified files:
> > > cm3/m3-libs/sysutils/src/POSIX/: m3makefile 
> > > 
> > > Log message:
> > > I had this change around: expose if we are using user threads, i.e. if we are OpenBSD
> > 

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