Re: WalSndWakeup() and synchronous_commit=off

Robert Haas <robertmhaas@gmail.com> writes:
> That definitely doesn't seem ideal - a lot of things can pile up
> behind WALWriteLock.  I'm not sure how big a problem it would be in
> practice, but we generally make a practice of avoiding sending signals
> while holding LWLocks whenever possible...

There's a good reason for that, which is that the scheduler might well
decide to go run the wakened process instead of you.  Admittedly this
tends to not be a problem on machines with $bignum CPUs, but on
single-CPU machines I've seen it happen a lot.

Refactoring so that the signal is sent only after lock release seems
like a good idea to me.
        regards, tom lane