From: Sam Roberts <sroberts@...>
Date: 2005-02-18T22:31:55+09:00
Subject: Re: pulling my hair out, why won't Kernel.sleep(0) sleep?

Quoteing matz@ruby-lang.org, on Fri, Feb 18, 2005 at 01:50:26PM +0900:
> Hi,
> 

> |Do you have any idea why this should be? What does Kernel.sleep(0)
> |actually do?
> 
> I guess it was busy looping, but there were other threads to work
> sometimes.  sleep(0) does not sleep but causes context switch.

That describes what I saw, kindof (race conditions are inherently
weird).

Thanks,
Sam

Here's a start to the docs, but I don't know if my description is
correct!

 /*
  *  call-seq:
- *     sleep(duration=0)    => fixnum
+ *     sleep(duration)    => fixnum
+ *     sleep()            => fixnum
  *  
- *  Suspends the current thread for _duration_ seconds (which may be
- *  any number, including a +Float+ with fractional seconds). Returns the actual
- *  number of seconds slept (rounded), which may be less than that asked
- *  for if the thread was interrupted by a +SIGALRM+, or if
- *  another thread calls <code>Thread#run</code>. An argument of zero
- *  causes +sleep+ to sleep forever.
- *     
+ *  Suspends the current thread for _duration_ seconds (which may be any
+ *  number, including a +Float+ with fractional seconds).  Calling sleep with
+ *  no arguments causes +sleep+ to sleep "forever" - where "forever" means
+ *  until it is woken up, see below. Calling sleep with an argument of
+ *  +0+ causes a context switch, if another thread is ready to be
+ *  scheduled.
+ *
+ *  Returns the actual number of seconds slept (rounded), which may be less
+ *  than that asked for if the thread was interrupted by a +SIGALRM+, or if
+ *  another thread calls <code>Thread#run</code>.
+ *
+ *  WHAT ABOUT OTHER SIGNALS?
+ *
  *     Time.new    #=> Wed Apr 09 08:56:32 CDT 2003
  *     sleep 1.2   #=> 1
  *     Time.new    #=> Wed Apr 09 08:56:33 CDT 2003