Re: Multiplexing SUGUSR1

It's required by the sync replication patch, but has no value otherwise.

Bruce Momjian wrote:
> Is this for 8.4?
>
> ---------------------------------------------------------------------------
>
> Heikki Linnakangas wrote:
>> I've been looking at the signal handling part of the synchronous
>> replication patch. It looks OK, but one thing makes me worry.
>>
>> To set or clear the flag from PGPROC, to send or handle a signal, we
>> have to acquire ProcArrayLock. Is that safe to do in a signal handler?
>> And is the performance impact of that acceptable?
>>
>>
>> Another observation is that the patch introduces a new function called
>> SendProcSignal. Nothing wrong with that, except that there's an existing
>> function called ProcSendSignal, just above SendProcSignal, so there's
>> some potential for confusion. The old ProcSendSignal function uses the
>> per-backend semaphore to wake up a backend. It's only used to wait for
>> the cleanup lock in bufmgr.c. I'm tempted to remove that altogether, and
>> use the new signal multiplexing for that too, but OTOH if it works,
>> maybe I shouldn't touch it.
>>
>> Attached is a patch with some minor changes I've made. Mostly cosmetic,
>> but I did modify the sinval code so that ProcState has PGPROC pointer
>> instead of backend pid, so that we don't need to search the ProcArray to
>> find the PGPROC struct of the backend we're signaling.
>>
>> --
>> Heikki Linnakangas
>> EnterpriseDB http://www.enterprisedb.com
>
>
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--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com