Horton

Re: make MaxBackends available in _PG_init

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Julien Rouhaud <rjuju123@gmail.com>, Andres Freund <andres@anarazel.de>, Michael Paquier <michael@paquier.xyz>, "Bossart, Nathan" <bossartn@amazon.com>, Fujii Masao <masao.fujii@oss.nttdata.com>, "wangsh.fnst@fujitsu.com" <wangsh.fnst@fujitsu.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Greg Sabino Mullane <htamfids@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2022-04-18T23:33:54Z
Lists: pgsql-hackers 
Nathan Bossart <nathandbossart@gmail.com> writes:
> I noticed that requests for more LWLocks follow a similar pattern as
> regular shared memory requests, and I figured that we would want to do
> something similar for those, but I wasn't sure exactly how to proceed.  I
> saw two options: 1) use shmem_request_hook for both regular requests and
> LWLock requests or 2) introduce an lwlock_request_hook.  My instinct was
> that option 1 was preferable,

Yeah, I agree, which says that maybe the hook name needs to be something
else (not that I have a good proposal).

> but AFAICT this requires introducing a new
> external variable for inspecting whether the request is made at a valid
> time.

Uh, why?  It'd be the core code's responsibility to place the hook
call at a point where you could do both.

			regards, tom lane

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