Re: Question whether a problem with race conditions exists in this case

Tom Anderson <>
Thu, 15 Dec 2011 14:44:39 +0000
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On Wed, 14 Dec 2011, Saxo wrote:

On Dec 14, 10:26?pm, Eric Sosman <esos...@ieee-dot-org.invalid> wrote:

? ?private Object lock = new Object();

? ? ?What does `lock' buy you? ?Why not just synchronize on the
Node itself?

The purpose is only to indicate that some more fine-gtrained locking
would be used for the real thing instead of doing a synchronized(this)
{ ... } thing.

It's quite a common pattern. I'm always a bit dubious about using an
public object (FSVO 'public') as the victim of a synchronized block; how
do i know some random other bit of code in some other thread isn't going
to try to lock the object at some point, and cause trouble? You wouldn't
expose a field, would you? So why expose an object's lock? Essentially, i
see an object's lock as a feature, like a method or a field; it should
only be exposed to other classes after due consideration, and if it is,
its proper use should be documented.

The locking analogue of a private field is an object like the above,
created for the sole purpose of supplying a lock that is provably only
accessible to code which can see the private details of the class.

I have coined the name 'lockguffin' for these objects, and i encourage you
all to use it.


And the future is certain, give us time to work it out

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