Re: Some experience with the igc branch

[Gerd Möllmann]

Helmut Eller <eller.helmut@gmail.com> writes:

> On Wed, Dec 25 2024, Gerd Möllmann wrote:
>
>> Pip Cet <pipcet@protonmail.com> writes:
>>
>>> I don't think that's the problem.  The problem is that signals can
>>> interrupt MPS, on all platforms.
> [...]
>> And I don't think that's right :-). It's completely right that in the
>> SIGPROF handler everything can be inconsistent. That's true both for MPS
>> and Emacs. For example, the bindings stack (specpdl) may be inconsistent
>> when SIGPROF arrives. Literally everything we do in the SIGPROF runs the
>> risk of encountering inconsistencies.
>
> The SIGPROF handler copies part of the potentially inconsistent state to
> the profiler log.  That same potentially inconsistent profiler log is
> used later, outside the signal handler.  Sounds like a problem to me.
> Is it not?  Or is the probability for inconistencies being copied so low
> that we ignore it?
>
> Helmut

I think the latter, i.e. we ignore it. I think, but I can't prove
anything, that the probability is good that we get away with it. For
example, We're only using the backtrace_p binding stack entries,
so the GIGPROF would have to happen when in some code putting them to be
in danger, so to speak. That's not so likely, I think.