Re: Synchronization Question

From:
Knute Johnson <nospam@rabbitbrush.frazmtn.com>
Newsgroups:
comp.lang.java.programmer
Date:
Sun, 13 Sep 2009 18:42:09 -0700
Message-ID:
<4aad9f70$0$17297$b9f67a60@news.newsdemon.com>
Patricia Shanahan wrote:

At the most flexible, it could merely mean that you want the final value
of each element to be one of the values written to it if it was written,
and the original value if it was never written. In that case, you just
need to make sure that each thread does something that causes its writes
to happen-before any read of the array. For example, any write by a
thread happens-before any read that follows a join that detects its
termination.


The OP doesn't need to synchronize for contention because of the atomic
writes of ints. He needs visibility by the reading thread. Is this a
possible situation to use the universal visibility of volatile write/read?

Each of the OPs array modifying threads would write to a common volatile
variable as the last action before terminating. Prior to reading the
array, the reading thread reads the common volatile variable and all
variables written to by the writing threads will be now be visible to
the reading thread.

 From my re-reading Java Concurrency In Practice it is not clear to me
either way (see pages 38,39). Not sure how one could test this.

--

Knute Johnson
email s/nospam/knute2009/

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