[Vm-dev] unresponsive 64-bit Spur StackInterpreter, except...

[Ben Coman]

On Tue, Jul 14, 2015 at 8:11 AM, Eliot Miranda <eliot.miranda at gmail.com> wrote:
>
> Hi All,
>
>      I've a bit of a mystery and could do with suggestions of what to look for.  The 64-bit Spur StackInterpreter VM on linux was working fine up until a few months ago.  Now it doesn't respond to input, unless that is, I put various breakpoints on various functions along the chain from aioPool through to allocateInputEvent to signalExternalSemaphore to doSignalExternalSemaphores when ... it can suddenly start working?!  I'm planning to add a -debugeventchain flag or some such and if set write a different character to stderr form each function along the chain so I can see where the blockage is,

> but I fear heisenbugs; doing output could perturb the system into working (given that gdb can perturb the system also).

If that proves to be the case, maybe -debugeventchain=<letter>
where it only outputs that one letter at a time.

Or write to stderr from another thread so the main thread only writes
to a memory location - one for each point in the chain - could be
counters. That output thread could sleep for a while before
outputting.

> And I'm lazy so I wondered if anyone had a good idea.  I've thought of it being thread-related but that's not the case as all event processing in X11 happens on the main VM thread.  Anyway, I'm open to suggestions.

Labour intensive's all I got.

cheers -ben