From: Bob Alexander <bobalex@...>
Date: 2002-03-13T02:06:20+09:00
Subject: Re: Some potential RCRs

"Paul Brannan" wrote

> As an alternative, I would suggest a wrapper around the current Mutex
> object.  There's a name for this kind of mutex, but I can't remember
> what it is.

It has various names -- Python calls it RLock ("R" for recursive, as opposed
to Lock). Java, which fancies itself a multi-threaded, performant language
doesn't have a non-recursive lock. My thought is that Ruby doesn't need a
non-recursive mutex. Non-recursive mutexes (muti?) only make sense in
low-level performance-sensitive code where the saving of a couple of machine
cycles is an issue. (If you are that performance-oriented, then Ruby isn't
your choice.) Other than that, their non-recursiveness serves no useful
purpose (except to cause deadlocks  :-). Nested locks, on the other hand,
are very useful, allowing higher level methods which acquire the mutex to
call lower level methods which also have to acquire the mutex.

I suggest just changing the current Mutex to be recursive. I don't think
that would introduce any compatibility issues.


Bob