Re: Connections hang indefinitely while taking a gin index's LWLock buffer_content lock

On Thu, Dec 13, 2018 at 10:46 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2018-12-13 22:40:59 +0300, Alexander Korotkov wrote:
> > It doesn't mater, because we release all locks on every buffer at one
> > time. The unlock order can have effect on what waiter will acquire
> > the lock next after ginRedoDeletePage(). However, I don't see why one
> > unlock order is better than another. Thus, I just used the rule of
> > thumb to not change code when it's not necessary for bug fix.
>
> I think it's right to not change unlock order at the same time as a
> bugfix here. More generally I think it can often be useful to default
> to release locks in the inverse order they've been acquired - if there's
> any likelihood that somebody will acquire them in the same order, that
> ensures that such a party would only need to wait for a lock once,
> instead of being woken up for one lock, and then immediately having to
> wait for the next one.

Good point, thank you!

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company