[Bordeaux-threads-devel] with-timeout abstraction leaks a bit?

[Stelian Ionescu]

On Fri, 2009-12-18 at 11:57 -0800, Peter Seibel wrote:
> Well, the use I had for it was I needed to wait on a condition
> variable with a timeout. I.e. wait until the condition was notified or
> a certain amount of time had passed. In Allegro there was a direct way
> of doing that but there wasn't in Bordeaux Threads so I had to roll my
> own. If Bordeaux Threads wants to provide a way of doing that I'll be
> happy (at least for now). Though I'm not sure I see that WITH-TIMEOUT
> deserves to be totally removed--you may need to exercise some care
> about what you put inside a WITH-TIMEOUT but it seems that it
> shouldn't be drastically worse than any code that, say, calls a
> user-provided function (which could also signal a condition at a more
> or less random time.) Unless you're saying it's hard/impossible to
> implement safely within the Lisp implementation. That I wouldn't know
> about.

The problem is that the only general way to implement timeouts is to use
alarm(2) which asks the kernel to send SIGALRM after a certain amount of
time, and mixing signals and condition variables is very prone to errors
- the example given by Martin is a typical case of resource leak caused
by asynchronous unwinds

-- 
Stelian Ionescu a.k.a. fe[nl]ix
Quidquid latine dictum sit, altum videtur.
http://common-lisp.net/project/iolib
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