[reactive] Re: black hole detection and concurrency

Conal Elliott conal at conal.net
Wed Jan 7 22:39:16 EST 2009

Hi Simon,

That's great news.  Please let me know when there's a build I can grab, and
I'll try it out.

Regards,   - Conal

On Wed, Jan 7, 2009 at 7:22 AM, Simon Marlow <marlowsd at gmail.com> wrote:

> The bugs that we have identified result in deadlocks - the runtime doesn't
> notice that a thread blocked in throwTo can continue.  I can't think of a
> way that this could lead to bogus <<loop>>, but I suppose I wouldn't be too
> surprised if it were possible.
> The best way forward is for you to test out a snapshot once these patches
> have made it into a build.  Does that sound reasonable?  I've been running
> your TestRace program for quite a while on 4 processors without any hangs
> now.
> Cheers,
>        Simon
> Conal Elliott wrote:
>> I don't know if the bug would explain <<loop>>.  My guess is that the
>> black-hole-detection code is incorrectly concluding there is a black hole
>> because a thunk was marked as in the process of being evaluated, then the
>> evaluating thread is killed without unmarking the thunk, and then another
>> thread needs the whnf.  This is a fairly naive guess.  I don't know this
>> machinery well enough to have confidence.
>> What do you think?
>>   - Conal
>> On Tue, Jan 6, 2009 at 6:27 AM, Simon Marlow <marlowsd at gmail.com <mailto:
>> marlowsd at gmail.com>> wrote:
>>    Conal Elliott wrote:
>>        Indeed -- many thanks to Bertram, Sterling, Peter & others for
>>        the help!  I think getting this bug fixed will solve Reactive's
>>        mysterious bugs and unblock its progress.
>>    Ok, we can fix the fairly simple bug that a thread created in
>>    blocked mode blocks throwTos after the thread has finished.  But I'm
>>    slightly suspicious of the <<loop>> results you were getting - does
>>    this bug explain those too?
>>    Cheers,
>>           Simon
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