Deadlock falsely detected when using condition variables

I have a fragment of multi-threaded code using Ruby’s Mutex and
ConditionVariable class, where it appears that the interpreter
is calling a deadlock incorrectly.

I’m using ruby 1.8.6 on Windows XP.

The code in question looks like this:

@mutex = Mutex.new
@condition = ConditionVariable.new

@mutex.synchronize {
@condition.wait(@mutex) until @data_ready
… use data…
@data_ready = false
}

And the producer thread says:

@mutex.synchronize {
… make data available…
@data_ready = true
@condition.signal
}

Now sometimes the call to synchronize in the producer cause a deadlock,
which shows the two threads to be both sleeping, one in the condition
wait, one in the producer’s synchronise call.

This should never happen… the condition is meant to atomically release
the mutex as it goes to sleep.

Whats happening here folk?

Clifford H…

Whats happening here folk?
What patchlevel of 1.8.6 are you using ? 1.8.6-p0 is completely broken
w.r.t. thread support. 1.8.6 p36 and p110 are better.

Sylvain

Clifford H. wrote:

What patchlevel of 1.8.6 are you using ? 1.8.6-p0 is completely broken
w.r.t. thread support. 1.8.6 p36 and p110 are better.

My ruby -v said p0, but the install actually came from the latest
one-click
installer, which calls itself 186-25. I don’t know what the -25 means,
but
there seems to be no newer one-click installer.

Do I have to build the current ruby from source, or is there a newer
one-click installer?

Clifford H…

Sylvain J. wrote:

Whats happening here folk?
What patchlevel of 1.8.6 are you using ? 1.8.6-p0 is completely broken
w.r.t. thread support. 1.8.6 p36 and p110 are better.

Craaap! It’s patch -p0! How can such a fundamental thing be so
catastrophically broken?
Are there no test suites? I’ve been blaming myself for three hours
now…

Thanks for much for setting me straight… I’ll get a new version right
away.

Clifford H…

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs