Re: Synchronization Question

From:
Knute Johnson <nospam@rabbitbrush.frazmtn.com>
Newsgroups:
comp.lang.java.programmer
Date:
Sun, 13 Sep 2009 18:59:34 -0700
Message-ID:
<4aada385$0$17249$b9f67a60@news.newsdemon.com>
Lew wrote:

Knute Johnson wrote:

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.


This [1] would work, as elucidated in the JLS's discussion of
'happens-before'[2], but Patricia's suggestion of using 'join()' seems
simpler and easier.


Now that I think about it you do have a point (and so did Patricia).

[1] The array variable could be volatile, too.


A volatile array variable doesn't have volatile elements.

[2] It's really worth reading the JLS.


--

Knute Johnson
email s/nospam/knute2009/

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