Horton

Re: make MaxBackends available in _PG_init

Nathan Bossart <bossartn@amazon.com>

View thread View on postgr.es
From: "Bossart, Nathan" <bossartn@amazon.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Fujii Masao <masao.fujii@oss.nttdata.com>, "wangsh.fnst@fujitsu.com" <wangsh.fnst@fujitsu.com>, Andres Freund <andres@anarazel.de>, "Bharath Rupireddy" <bharath.rupireddyforpostgres@gmail.com>, Greg Sabino Mullane <htamfids@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2022-01-10T19:01:32Z
Lists: pgsql-hackers 
On 1/7/22, 12:27 PM, "Robert Haas" <robertmhaas@gmail.com> wrote:
> On Fri, Jan 7, 2022 at 1:09 PM Bossart, Nathan <bossartn@amazon.com> wrote:
>> While that approach would provide a way to safely retrieve the value,
>> I think it would do little to prevent the issue in practice.  If the
>> size of the patch is a concern, we could also convert MaxBackends into
>> a macro for calling GetMaxBackends().  This could also be a nice way
>> to avoid breaking extensions that are using it correctly while
>> triggering ERRORs for extensions that are using it incorrectly.  I've
>> attached a new version of the patch that does it this way.
>
> That's too magical for my taste.

Fair point.  v4 [0] is the less magical version.

Nathan

[0] https://postgr.es/m/attachment/125445/v4-0001-Disallow-external-access-to-MaxBackends.patch

Commits

  1. Add a new shmem_request_hook hook.

  2. Remove non-functional code for unloading loadable modules.

  3. Fix misleading comments about background worker registration.

  4. Revert the addition of GetMaxBackends() and related stuff.

  5. Fix typo in multixact.c

  6. Reduce more the number of calls to GetMaxBackends()

  7. Remove MaxBackends variable in favor of GetMaxBackends() function.

  8. Fix comments about bgworker registration before MaxBackends initialization

  9. Fix bogus assertion in BootstrapModeMain().

  10. Make sure MaxBackends is always set