Re: SIGPROF + SIGCHLD and igc

[Helmut Eller]

On Fri, Dec 27 2024, Eli Zaretskii wrote:
[...]
> You are basically describing the way SIGPROF emulation is implemented
> on Windows (see w32proc.c for the details).  But I don't understand
> why you need that pipe: doesn't pthreads allow one thread to stop the
> other?  If so, just make the "profiler thread" stop the main thread
> instead of your step 2, and resume the main thread instead of your
> step 4.  Am I missing something?

Here another observation: Let's assume that we can emulate SuspendThread
and ResumeThread on POSIX and MacOS (much like MPS does it).  In the
profiler thread we can then simply do:

   SuspendThread (<main-thread>)
   get_backtrace ()
   ResumeThread (<main-thread>)

without invoking any SIGPROF handler or the need for
ArenaEnter/ArenaLeave.

The only complication seems to be, that we must avoid deadlocks when MPS
tries to suspend a thread is already suspended by our emulation.

Helmut