Re: Recovery control functions

On 14.01.2011 14:01, Simon Riggs wrote:
> On Fri, 2011-01-14 at 13:47 +0200, Heikki Linnakangas wrote:
>> On 14.01.2011 13:15, Simon Riggs wrote:
>>>   /*
>>> + * Recheck shared recoveryPause by polling.
>>> + *
>>> + * XXX It might seem we should do this via a shared Latch, but
>>> + * currently we only support one shared latch per process and
>>> + * that is already taken for Startup process. Polling is used
>>> + * in other places in xlog.c already, so not a concern.
>>> + */
>>
>> There is no such limitation with latches.
>
> SIGUSR1 handler can only handle one shared latch

You can only *wait* for one latch at a time, but you can own more than 
that. AFAICS you would never need to wait for the recovery-pause-latch 
at the same time as the other latch.

(That you can't wait for more than one latch at a time isn't a 
limitation of the SIGUSR1 handler either. The signal handler and the 
self-pipe mechanism wouldn't need any changes to support multi-latch 
waits. We're just missing a WaitMultipleLatches() function that would 
check the is_set flag on multiple latches.)

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com