Re: MPS: User GC customizations

["Gerd Möllmann" <gerd.moellmann@gmail.com>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Gerd Möllmann <gerd.moellmann@gmail.com>
>> Cc: Ihor Radchenko <yantar92@posteo.net>,  Eli Zaretskii <eliz@gnu.org>,
>>   emacs-devel@gnu.org,  eller.helmut@gmail.com
>> Date: Thu, 04 Jul 2024 18:07:42 +0200
>> 
>> Pip Cet <pipcet@protonmail.com> writes:
>> 
>> > I think we can just set flags for "called MPS" and "in a scan
>> > function" and look at them in the SIGPROF handler to distinguish the
>> > four cases?
>> 
>> Not sure. What if MPS calls these in its own thread? I guess that
>> wouldn't be so interesting for Ihor.
>
> AFAIU, on GNU/Linux signals are delivered to the main thread,

Pip mentioned scan functions, so let's say we set a flag in_scan while
being in dflt_scan. MPS now calls dflt_scan, in the MPS thread, to do an
increment of its work. While in dflt_scan we get SIGPROF and land in the
signal handler in main thread, and the profiler sees in_scan == true.

Q: do we count that as part of GC work that the profiler should report,
although it happened in the MPS thread? I understood Ihor as saying that
he doesn't want that.