Shared buffer access rule violations?

From: Asim R P <apraveen(at)pivotal(dot)io>
To: PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org>
Subject: Shared buffer access rule violations?
Date: 2018-07-11 00:15:13
Message-ID: CANXE4Te4G0TGq6cr0-TvwP0H4BNiK_-hB5gHe8mF+nz0mcYfMQ@mail.gmail.com
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Hi,

In order to make changes to a shared buffer, one must hold a pin on it
and the content lock in exclusive mode. This rule seems to be
followed in most of the places but there are a few exceptions.

One can find several PageInit() calls with no content lock held. See,
for example:

fill_seq_with_data()
vm_readbuf()
fsm_readbuf()

Moreover, fsm_vacuum_page() performs
"PageGetContents(page))->fp_next_slot = 0;" without content lock.

There may be more but I want to know if these can be treated as
violations before moving ahead.

Asim

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