Re: SIGPROF + SIGCHLD and igc

[Helmut Eller]

On Sat, Dec 28 2024, Pip Cet wrote:

>> I think I see what you mean.  I imagine the profiler thread to be a loop
>> like
>>
>>   while (true) {
>>      sleep (<x-seconds>)
>>      ArenaEnter (<arena>)
>>        pthread_kill (SIGPROF, <main-thread>)
>>        wait (<pipe>)
>>      ArenaLeave (<arena>)
>>   }
>
> I'm not really following.  Did you mean to include a call to a "clear
> all memory barriers" function after the ArenaEnter call?  If not, the
> SIGPROF handler (and all handlers interrupting the SIGPROF handler which
> aren't being delayed) would not be able to access MPS memory, which I
> thought was the goal.

In my mind it works like this: when the SIGPROF handler tries to access
MPS memory, the SIGSEGV handler kicks in as it usually would in a
non-signal handler context.  This should work because at the beginning
of the SIGPROF handler we guarantee that MPS doesn't hold the arena
lock.

Helmut