[gambit-list] Experiencing freeze error in |##thread-effective-priority-downgrade!| , a btq became self-referencing so all stops, any thoughts on how fix?

Marc Feeley feeley at iro.umontreal.ca
Thu May 2 20:58:53 EDT 2013


On 2013-05-02, at 8:05 PM, Mikael <mikael.rcv at gmail.com> wrote:

> Hi Marc!
> 
> 
> Rarely I get an error that Gambit just stops, while eating up all the CPU core.
> 
> It's so rare that I don't consider it a problem, though I'd be happy to see it gone of course.
> 
> I believe 50% of the time it happens within 5 seconds after Gambit started and thread-start! was invoked 1-5 times.
> 
> I ran into this error now, saw it something like four times in 6mo.
> 
> This is on Gambit gsc 4.6.6 on AMD64, compiled from source with --enable-single-host and some more.
> 
> The Gambit session is running a couple of Gambit threads, absolutely nothing exotic going on.
> 
> Had it in a GDB session so could reliably "profile" the error, output from that GDB session below.
> 
> Saved the core file for later reference too.
> 
> It's in _thread.scm , and from what I can see it's in |##thread-effective-priority-downgrade!|'s definition.
> 
> What it looks like to me is that by some reason we've got a self-referencing btq-deq-next chain element, that
> keeps it reiterating forever.
> 
> I base this on that ___r1 and ___r3 and ___r4 remain constant; I'd guess that ___r1 is thread, ___r3 is btq and ___r4 is leftmost.
> 
> 
> 
> Do you have any thought on what the issue might be, or any on how I can track this further?

Could you describe the threads that are running?  Are they of different priorities, and if so, what are they?

Marc

P.S. For bugs like this, could you use the github issue tracker?  It will simplify tracking the issue.




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