setnumcapabilities001 failure

Ryan Yates fryguybob at
Thu Oct 27 16:10:00 UTC 2016

Briefly looking at the code it seems like several global variables involved
should be volatile: n_capabilities, enabled_capabilities, and
capabilities.  Perhaps in a loop like in scheduleDoGC the compiler moves
the reads of n_capabilites or capabilites outside the loop.  A failed
requestSync in that loop would not get updated values for those global
pointers.  That particular loop isn't doing that optimization for me, but I
think it could happen without volatile.


On Thu, Oct 27, 2016 at 9:18 AM, Ben Gamari <ben at> wrote:

> Simon Marlow <marlowsd at> writes:
> > I haven't been able to reproduce the failure yet. :(
> >
> Indeed I've also not seen it in my own local builds. It's quite an
> fragile failure.
> Cheers,
> - Ben
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> ghc-devs mailing list
> ghc-devs at
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