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