Re: [HACKERS] 'Waiting on lock'

"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> Gregory Stark <stark(at)enterprisedb(dot)com> writes:
>> Is it possible for unlocking the semaphore to wake another process other than
>> our own? In which case checking log_lock_waits before signalling the semaphore
>> arguably locks us into having log_lock_waits be PGC_POSTMASTER.
>
> How you figure that?

Well I'm not clear exactly what's going on with the semaphores here. If it's
possible for to be printing the messages only as a result of another backend
unlocking the semaphore then making the PGSemaphoreUnlock conditional on
log_lock_waits means you can't enable log_lock_waits after startup and get
deterministic behaviour because whether you get messages will depend on which
other backend happens to wake you up.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com