Re: [ID 19991229.003] perl 5.005_03 core dumps -- signal

[Joshua N Pritikin <joshua.pritikin@db.com>]

On Wed, Jan 12, 2000 at 10:18:24AM -0500, dan@sidhe.org wrote:
> At 09:54 AM 1/12/00 -0500, Joshua N Pritikin wrote:
> >I usually give up at this point because I can see that signals are a
> >mess and getting them to work with multiple threads is going to make it
> >worse.  I am encouraged to hear that linux does not follow POSIX.  My
> >experience with POSIX threads has not been very encouraging.
> 
> I wouldn't get too encouraged. Linux threads are an attempt to shoehorn 
> POSIX threads onto a system that actively disapproves of them. The big 
> issues are signals and process table exhaustion, but there are other niggly 
> things. (Each thread has a separate pid, for example, and the kernel 
> doesn't really know what 'process' a thread belongs to)

So what?  I know (from kernel traffic) they are aware of and fixing the
process table exhaustion...

> >My
> >unsubstantiated suspicion is that the POSIX thread spec was written well
> >ahead of any working implementation. I think it is likely that the linux
> >model is better even though I haven't checked myself.  This is just a
> >vague feeling.  I might be completely backwards here.
> 
> In some ways its worse. Because threads are really separate processes,

What's the difference?  Memory sharing is the same, right?

> only the thread that actually gets the signal delivered can see it.

Yes.  That's one of the reasons I felt that linux might be an
improvement over the POSIX mess.

> Not 
> necessarily a bad thing (though it makes separate signal-handling threads 
> trickier)

I never understood the alure of routing all the signals to a single
signal-handling thread.  Can anyone comment on this?

> but it is in direct contradiction to the standard they're 
> implementing.

True.

> (And for all its limits, POSIX threads were designed by a 
> bunch of experienced, clever guys who got a standard that managed to meet 
> the requirements of the folks involved. I'm not sure that the Linux changes 
> have that level of experience behind their changes)

As seen from here, that doesn't sound conclusive one way or the other.

-- 
"Never ascribe to malice that which can be explained by stupidity."
                            via, but not speaking for Deutsche Bank

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Follow-Ups from:

Dan Sugalski <dan@sidhe.org>

References to:

Joshua N Pritikin <joshua.pritikin@db.com>
Dan Sugalski <dan@sidhe.org>

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