[concurrency-interest] Proper workaround for FutureTask.set()/get() race (CR 7132378)
nathan.reynolds at oracle.com
Mon Apr 23 12:37:32 EDT 2012
Consider throwing an exception instead of returning false. The
exception will force the caller to deal with the already set condition.
Returning false is a bug waiting to happen.
Calling set() twice usually indicates a larger bug in the caller code.
Why would the algorithm call it twice? Is there a race between 2
threads in the caller code? Is one part of the caller code not aware of
what the other part of code did?
I raise this concern because FindBugs flags issues if the caller doesn't
deal with the result of the java.io.File and java.util.concurrent.Lock
APIs. For many that don't use FindBugs, they will have a lot of bugs.
Consulting Member of Technical Staff | 602.333.9091
Oracle PSR Engineering <http://psr.us.oracle.com/> | Server Technology
On 4/21/2012 1:33 PM, Joe Bowbeer wrote:
> On Sat, Apr 21, 2012 at 12:08 PM, Aleksey Shipilev wrote:
> Yes. SettableFuture-like class is something missing from concurrent
> classes I'm redoing over and over again in most of the projects.
> Implementing it directly on top of AQS might provide some benefits
> comparing to extending from FutureTask? Oh wait, it smells like
> API enhancement proposal? :)
> Bill Pugh once suggested a separate concurrency abstraction: an
> externally settable FutureValue<V>, which supports the following methods:
> V get() - Waits if necessary for the value to be set, and then
> returns the value.
> boolean isDone() - Returns true if the value is set
> boolean set(V v) - Sets the value if it was not already set.
> Returns true if the value was set by this call, false if it
> was set by another call.
> Having set(v) return a boolean seems like a good idea. What do you think?
> To this I would also add the other Future methods such as cancel(),
> plus setException(). In other words, I envision FutureValue as a
> Future with two additional methods: boolean set(v) and boolean
> Are there any other Future enhancements that you think are sorely
> needed in j.u.c.?
> Concurrency-interest mailing list
> Concurrency-interest at cs.oswego.edu
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