| From: | Chapman Flack <chap(at)anastigmatix(dot)net> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, James Sewell <james(dot)sewell(at)jirotech(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Threading in BGWorkers (!) |
| Date: | 2020-06-24 01:50:26 |
| Message-ID: | 5EF2B162.9030601@anastigmatix.net |
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| Lists: | pgsql-hackers |
On 06/23/20 21:44, Andres Freund wrote:
> I think that's way harder than what you make it sound here. The locking
> for shm_mq doesn't really work inside a process. In contrast to the
> single threaded case something like a volatile write to
> ParallelMessagePending doesn't guarantee much, because there's no
> guaranteed memory ordering between threads. And more.
It occurred to me after I sent the message this morning that my suggestion
(2) could subsume (1). And requires nothing more than a single volatile
write of a boolean, and getting called back at a convenient time on the
single main thread.
So perhaps I shouldn't have suggested (1) at all - just muddies the waters.
Regards,
-Chap
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