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From: Kyotaro Horiguchi <[email protected]>
To: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Subject: Re: Avoid unncessary always true test (src/backend/storage/buffer/bufmgr.c)
Date: Tue, 13 Jun 2023 16:39:21 +0900 (JST)
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CAEudQArzX-q7FuvHxcEQKP9RuM7eFw4CnvU_xQtkiu4+tnaA4A@mail.gmail.com>
	<CABwTF4W+WMr=3bjLP5-69+oG81BEZOH+SAqPX8GDnZry5==thA@mail.gmail.com>
	<[email protected]>

At Tue, 13 Jun 2023 15:11:26 +0900, Michael Paquier <[email protected]> wrote in 
> On Mon, Jun 12, 2023 at 10:51:24PM -0700, Gurjeet Singh wrote:
> > To me, it looks like these checks are a result of code being
> > copy-pasted from somewhere else, where this check might have been
> > necessary. The checks are sure not necessary at these spots.
> 
> I am not completely sure based on my read of the code, but isn't this
> check needed to avoid some kind of race condition with a concurrent
> backend may have worked on the relation when attempting to get the
> lock?

Gurjeet has mentioned that eb.rel cannot be modified by another
process since the value or memory is in the local stack, and I believe
he's correct.

If the pointed Relation had been blown out, eb.rel would be left
dangling, not nullified. However, I don't believe this situation
happens (or it shouldn't happen) as the entire relation should already
be locked.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

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