Re: Multiplexing SUGUSR1

Is this for 8.4?

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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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--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
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