Horton

Shared buffer access rule violations?

P <apraveen@pivotal.io>

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From: Asim R P <apraveen@pivotal.io>
To: PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Date: 2018-07-11T00:15:13Z
Lists: pgsql-hackers 
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

Commits

  1. Fix inadequate buffer locking in FSM and VM page re-initialization.