[Haskell-cafe] SIGVTALRM and Unbound threads

[Lane Seppala]

Hmm. Using your experiment, I didn't see any differing behavior from my
original example (both GHC 7.6.3 and 7.8.3). What should I have expected?

That being said, I hadn't tried sending SIGINT to the running process as
you suggested. Thanks for this idea. Both for my example and yours, it
takes two SIGINTs to kill the process. Interesting and surely not desired
behavior, but I might not understand what the implications are.

I ran each program with strace and sent SIGINTs to it while running. I
found it interesting that each program had paused emitting SIGVTALRMs until
I sent the first SIGINT, which then it resumed without interrupting the
sleep. The second SIGINT exited the process.

I'm even more curious &/ confused about the interaction of unbounded
threads and signals now, or if there's any interaction at all. The pausing
of the SIGVTALTRMs mentioned above makes me wonder whether it's the
unbounded thread or some auxiliary mechanism that helps prevent interrupts.

I'd love to have a deeper understanding of this interworking between
signals and unbounded threads. My own web scouring hasn't turned up
anything, but I'd be happy to be pointed somewhere.

Kindly,
Lane

On Thu, Sep 25, 2014 at 3:59 PM, Albert Y. C. Lai <trebla at vex.net> wrote:

> On 14-09-25 03:55 PM, Lane Seppala wrote:
>
>> As the simplest example, compiled with the threaded runtime (and
>> neglecting imports):
>>
>>      main = void $ sleep 10
>>
>> will be interrupted, whereas
>>
>>      main = void $ runInUnboundThread $ sleep 10
>>
>> will complete its 10 second sleep.
>>
>
> Before you commit to your understanding, consider one more experiment that
> changes everything:
>
> main = void $ runInUnboundThread (runInBoundThread $ sleep 10)
>
> Also, consider hitting CTRL-C (or sending SIGINT any way), see what does
> not happen. Do you want this behaviour?
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