[concurrency-interest] Single-threaded ForkJoinPool

Viktor Klang viktor.klang at gmail.com
Sat Feb 6 08:18:39 EST 2016


Try and report back :)

On Sat, Feb 6, 2016 at 1:05 PM, cowwoc <cowwoc at bbs.darktech.org> wrote:

> Interesting idea.
>
> By the looks of it, returning null causes ForkJoinPool to give up creating
> a new worker thread. If there are no active worker threads, then
> ForkJoinTask.get() hangs forever. Now, I wonder if it's safe to do as you
> mention... don't we run the risk of some sort of race conditions where the
> first thread shuts down at the exact same time that I reject the creation
> of the second thread and as a result ForkJoinTask.get() hangs forever?
>
> Gili
>
> On 2016-02-06 4:39 AM, Viktor Klang [via JSR166 Concurrency] wrote:
>
> What happens if you supply it with a thread factory which only allows a
> single thread to be alive at a time, and returns null if it already has
> returned a still living thread?
>
> --
> Cheers,
>> On Feb 6, 2016 05:19, "cowwoc" <[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=13234&i=0>> wrote:
>
>> Hi,
>>
>> Is this the correct mailing list for discussing ForkJoinPool in JDK9? If
>> not, please point me to the right place.
>>
>> I have a feature request for ForkJoinPool which doesn't seem to be
>> possible
>> to implement without a JDK change:
>> http://stackoverflow.com/q/34012134/14731
>>
>> Specifically, I need to be able to an application that uses Random and
>> ForkJoinPool in a deterministic manner when debugging/profiling but run
>> full-speed in normal execution mode. I have all the moving parts nailing
>> down except for ForkJoinPool.
>>
>> If I create ForkJoinPool with a parallelism of 1, sometimes I see two
>> worker
>> threads getting used. I am guessing that this is caused by
>> ForkJoinTask.get() invoking ForkJoinPool.common.externalHelpComplete(),
>> but
>> maybe something else is going on.
>>
>> Is there a way for me to guarantee that ForkJoinThread will use exactly 1
>> worker thread, no less, no more? Would you like me to file a formal
>> feature
>> request?
>>
>> Thank you,
>> Gili
>>
>>
>>
>> --
>> View this message in context:
>> http://jsr166-concurrency.10961.n7.nabble.com/Single-threaded-ForkJoinPool-tp13232.html
>> Sent from the JSR166 Concurrency mailing list archive at Nabble.com.
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-- 
Cheers,
√
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