Re: Is it OK to perform logging while holding a LWLock?

> On Feb 11, 2026, at 11:19, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Chao Li <li.evan.chao@gmail.com> writes:
>> As $SUBJECT says, my understanding is no.
>
> It's not a great idea, but I'm not sure it's fatal.  There are places
> that hold LWLocks for awhile.
>
>> I think LWLocks are generally only held for a very short duration,
>> like a few CPU cycles to read or modify some shared data,
>
> Spinlocks are treated that way, but we're willing to hold LWLocks
> longer.  The main thing I'd be concerned about is that there is no
> deadlock-detection infrastructure for LWLocks, so you'd better be
> darn certain there is no possibility of deadlock.  That usually
> means you want to limit the extent of code that could run while
> you're holding the lock.
>
> In your specific example, the thing I'd be afraid of is that an
> errcontext callback might do something you're not expecting.
> We don't forbid errcontext callbacks from doing catalog lookups,
> for instance.  So on the whole I agree with this patch, with
> or without any concrete example that fails.
>
> regards, tom lane

Thanks for the detailed explanation. I’ve written this down in my notebook, very helpful.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/