From: Joel VanderWerf <joelvanderwerf@...>
Date: 2014-04-17T11:57:39-07:00
Subject: [ruby-core:62080] Re: [ruby-trunk - Bug #9754] [Open] Ruby refuses to run source with Mutex locks though there is no hazard..

On 04/17/2014 03:48 AM, thomas.lynch@reasoningtechnology.com wrote:
> Bug #9754: Ruby refuses to run source with Mutex locks though there is no hazard..

A Mutex is not reentrant.

This deadlocks:

     m = Mutex.new
     m.lock
     m.synchronize {}

So does this:

     m = Mutex.new
     m.synchronize {m.synchronize {}}

But Monitor is reentrant, so the following does not deadlock:

     m = Monitor.new
     m.synchronize {m.synchronize {}}

There is no Monitor#lock, but there is MonitorMixin::ConditionVariable, 
which will do what you want.

(Btw, ruby-talk might be better for these questions than the forum.)