From: James Gray <james@...>
Date: 2008-03-18T22:54:48+09:00
Subject: Re: Thread#raise, Thread#kill, and timeout.rb are unsafe

On Mar 18, 2008, at 12:04 AM, Tanaka Akira wrote:

> In article <E1JaM9H-0000jj-AB@x61.netlab.jp>,
>  Yukihiro Matsumoto <matz@ruby-lang.org> writes:
>
>> What should safe point declaration mechanism look like?
>
> Basically, asynchronous events should be queued.
>
> * make a queue for each thread.
> * Thread#raise(exc) enqueue exc to the queue.
> * Thread.check_interrupt(klass) checks an exception which is
>  a kind of klass in the queue of the current thread.  If it
>  exists, the exception is raised.
> * other queue examining mechanism, such as sigpending, etc,
>  may be useful.

Perl went kind-of along these lines around version 5.8, if I recall  
correctly.  They added "safe signals" which were signals that only  
interrupted at times when it was safe for them to do so.

This did have a few weird side-effects though.  For example, running a  
complex regex would shutoff signal handling for the duration.  That  
meant you could no longer timeout a regex.

Perhaps they've fixes these issues now, but I remember the change was  
not as smooth as they had hoped it would be.

James Edward Gray II