Horton

Re: pg11.1: dsa_area could not attach to segment

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Sergei Kornilov <sk@zsrv.org>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2019-02-14T16:20:10Z
Lists: pgsql-hackers 
On Fri, Feb 15, 2019 at 01:12:35AM +1300, Thomas Munro wrote:
> The problem is that a DSM handle (ie a random number) can be reused
> for a new segment immediately after the shared memory object has been
> destroyed but before the DSM slot has been released.  Now two DSM
> slots have the same handle, and dsm_attach() can be confused by the
> old segment and give up.
> 
> Here's a draft patch to fix that.  It also clears the handle in a case
> where it wasn't previously cleared, but that wasn't strictly
> necessary.  It just made debugging less confusing.

Thanks.

Do you think that plausibly explains and resolves symptoms of bug#15585, too?

Justin

Commits

  1. Fix race in dsm_attach() when handles are reused.

  2. Refactor pid, random seed and start time initialization.