Re: MPS: profiler

[Gerd Möllmann]

Eli Zaretskii <eliz@gnu.org> writes:

>> >> Yes, the SIBPROF handler could at least return early then.
>> >
>> > Perhaps something like this?
>> 
>> Not sure. The result of is_busy is only valid at the point in time when
>> it is called.
>
> Are you thinking about what happens when GC is run concurrently?
> Because this is not what happens here, AFAIU.  Let's focus on fixing
> the actual issue we see in the backtrace, and consider its possible
> generalizations later.
>
> Are you saying that is_busy could return false in the situation we see
> in the backtrace, i.e. during the entire time MPS processes its
> protection-induced SIGSEGV?

I'm still not sure. What I'm trying to say is that we need to be sure
that there are no windows left in which things can change. I'd be most
comfortable ATM if the first thing the SIGPROF handler does is check
is_busy and immediately returns, doing nothing.