Horton

Re: Weaker shmem interlock w/o postmaster.pid

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Noah Misch <noah@leadboat.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2014-02-12T23:06:40Z
Lists: pgsql-hackers 
On Wed, Sep 11, 2013 at 02:10:45PM -0400, Robert Haas wrote:
> On Tue, Sep 10, 2013 at 11:33 PM, Noah Misch <noah@leadboat.com> wrote:
> > I'm thinking to preserve postmaster.pid at immediate shutdown in all released
> > versions, but I'm less sure about back-patching a change to make
> > PGSharedMemoryCreate() pickier.  On the one hand, allowing startup to proceed
> > with backends still active in the same data directory is a corruption hazard.
> > On the other hand, it could break weird shutdown/restart patterns that permit
> > trivial lifespan overlap between backends of different postmasters.  Opinions?
> 
> I'm more sanguine about the second change than the first.  Leaving
> postmaster.pid around seems like a clear user-visible behavior change
> that could break user scripts or have other consequences that we don't
> foresee; thus, I would vote against back-patching it.  Indeed, I'm not
> sure it's a good idea to do that even in master.  On the other hand,
> tightening the checks in PGSharedMemoryCreate() seems very much worth
> doing, and I think it might also be safe enough to back-patch.

Were these changes every applied?  I don't see them.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + Everyone has their own god. +

Commits

  1. Probe only 127.0.0.1 when looking for ports on Unix.

  2. Don't write to stdin of a test process that could have already exited.

  3. Test both 0.0.0.0 and 127.0.0.x addresses to find a usable port.

  4. MSYS: Translate REGRESS_SHLIB to a Windows file name.

  5. MSYS: Skip src/test/recovery/t/017_shm.pl.

  6. When Perl "kill(9, ...)" fails, try "pg_ctl kill".

  7. Consistently test for in-use shared memory.

  8. Revert "Consistently test for in-use shared memory."

  9. Silence -Wimplicit-fallthrough in sysv_shmem.c.

  10. Make src/test/recovery/t/017_shm.pl safe for concurrent execution.

  11. Update HINT for pre-existing shared memory block.

  12. Add WL_EXIT_ON_PM_DEATH pseudo-event.

  13. The default values for shared_buffers and max_connections are now 1000

  14. XLOG (and related) changes:

  15. Significant cleanups in SysV IPC handling (shared mem and semaphores).