Horton

Re: TopoSort() fix

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Michael Paquier <michael@paquier.xyz>, Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2019-07-30T04:06:02Z
Lists: pgsql-hackers 
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> On 2019-Jul-29, Tom Lane wrote:
>> FYI, I just got done inventing a way to reach that code, and I have
>> to suspect that it's impossible to do so in production, because under
>> ordinary circumstances no parallel worker will take any exclusive lock
>> that isn't already held by its leader.

> Hmm, okay, so this wasn't a bug that would have bit anyone in practice,
> yeah?  That's reassuring.

At the least, you'd have to go well out of your way to make it happen.

			regards, tom lane

Commits

  1. Add an isolation test to exercise parallel-worker deadlock resolution.

  2. Mark advisory-lock functions as parallel restricted, not parallel unsafe.

  3. Fix busted logic for parallel lock grouping in TopoSort().