From: MenTaLguY <mental@...>
Date: 2008-03-20T03:50:13+09:00
Subject: Re: Thread#raise, Thread#kill, and timeout.rb are unsafe

On Thu, 20 Mar 2008 02:29:09 +0900, Paul Brannan <pbrannan@atdesk.com> wrote:
> On Tue, Mar 18, 2008 at 02:04:40PM +0900, Tanaka Akira wrote:
>> It is because Thread.check_interrupt with blocking operations causes
>> race conditions.
> 
> Raising an exception during a blocking write operation makes it
> impossible to know how much data was written.
> 
> Similarly, raising an exception during a blocking read operation makes
> it impossible to access the data that was read.
> 
> The same is true for any operation for which partial success is
> possible.

That's a good point.  To some extent it is an API design and
implementation problem; an API which can partially "succeed" in that
fashion is arguably flawed.

There are really two alternatives:

 1. fix the operation so that it succeeds or fails atomically

 2. otherwise, make the operation always non-interruptable

(Well, there is also a third solution, used by Java's NIO for blocking
reads and writes: on interrupt, destroy the object in question so that
it doesn't matter anymore.  But I don't think it's a particularly good
solution.)

-mental