Re: Deadlock detector fails to activate on a hot standby replica

Dear Xuneng Zhou, All

Sorry for the delay. Starting from this moment I will use my personal email
vitprof(at)gmail(dot)com instead of vdavydov(at)postgrespro(dot)ru.

On 8/8/26 16:51, Xuneng Zhou wrote:
> I haven't looked into the details yet. This version seems not resolve
> the awkwardness of dependency you pointed out earlier. Just wondering
> the reason for not aiming higher. It seems not trivial but still
> feasible. Do you think we better try to land the bug fix first and do
> further refactoring based on that?

Yes, I haven't refactored the dependency. I think to fix the bug first
to continue progress, but refactor it later. I think the future
discussions about refactored versions may take a while.

> "I agree with your comment. Furthermore, I do not like the approach of
> locking and unlocking in different functions. But, I see this approach
> is used in some other places in the code. I should think about how to improve it.
>
> I have some doubts about the code where LockBufferForCleanup (bufmgr.c)
> calls ResolveRecoveryConflictWithBufferPin (standby.c), but the latter
> function calls BufferIsReadyForCleanup (bufmgr.c). There is an idea to
> refactor it in the future, because these functions are closely coupled.
> May be unite them or move ResolveRecoveryConflictWithBufferPin into
> bufmgr.c..."

I agree, it should be refactored. The problem is that BufferIsReadyForCleanup
uses some static variables from bufmgr.c. Moving
ResolveRecoveryConflictWithBufferPin
into bufmgr.c helps to break this dependency and looks good for me.

I have some thoughts about the term 'pin count waiter'. I think it is a
confusing name. There is an idea to name it as buffer writer, once
multiple-readers-single-writer lock is implemented here. Pin count waiter
is just another term for a buffer writer, I think.

I propose to go further with the current change to speed up the progress
because other contributors wait for it.

With best regards,
Vitaly Davydov
vitprof(at)gmail(dot)com (aka v(dot)davydov(at)postgrespro(dot)ru)
vitcpp(at)mail(dot)ru