On Fri, Nov 27, 2020 at 11:08:49AM -0800, Peter Geoghegan wrote: > On Fri, Nov 27, 2020 at 10:22 AM Heikki Linnakangas <hlinn...@iki.fi> wrote: >> I've made the mistake of forgetting to release an LWLock many times, >> leading to self-deadlock. And I just reviewed a patch that did that this >> week [1]. You usually find that mistake very quickly when you start >> testing though, I don't think I've seen it happen in production. > > +1. The fact that you don't get deadlock detection with LWLocks is a > cornerstone of the whole design. This assumption is common to all > database systems (LWLocks are generally called latches in the database > research community, but the concept is exactly the same).
+1. >> So yeah, I agree it's not worth spending cycles on this. Maybe it would >> be worth it if it's really simple to check, and you only do it after >> waiting X seconds. (I haven't looked at this patch at all) > > -1 for that, unless it's only for debug builds. Even if it is > practically free, it still means committing to the wrong priorities. > Plus the performance validation would be very arduous as a practical > matter. Looking at the git history, we have a much larger history of bugs that relate to race conditions when it comes to LWLocks. I am not really convinced that it is worth spending time on this even for debug builds, FWIW. -- Michael
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