Horton

Re: [HACKERS] Weaker shmem interlock w/o postmaster.pid

Daniel Gustafsson <daniel@yesql.se>

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From: Daniel Gustafsson <daniel@yesql.se>
To: Noah Misch <noah@leadboat.com>
Cc: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>, "9erthalion6@gmail.com" <9erthalion6@gmail.com>, "sfrost@snowman.net" <sfrost@snowman.net>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2019-04-01T08:19:56Z
Lists: pgsql-hackers 
On Monday, April 1, 2019 12:42 AM, Noah Misch <noah@leadboat.com> wrote:
> On Fri, Mar 29, 2019 at 09:53:51AM +0000, Daniel Gustafsson wrote:

> > This seems like a case where it would be useful to log a shmdt() error or do
> > an Assert() around the success of the operation perhaps?
>
> I'll add the same elog(LOG) we have at other shmdt() sites. I can't think of
> a site where we Assert() about the results of a system call. While shmdt()
> might be a justified exception, elog(LOG) seems reasonable.

Agreed, seems reasonable.

> > -   -   Loop till we find a free IPC key. Trust CreateDataDirLockFile() to
> > -   -   ensure no more than one postmaster per data directory can enter this
> > -   -   loop simultaneously. (CreateDataDirLockFile() does not ensure that,
> > -   -   but prefer fixing it over coping here.)
> >
> > This comment make it seem like there is a fix to CreateLockFile() missing to
> > his patch, is that correct? If so, do you have an idea for that patch?
>
> That comment refers to
> https://postgr.es/m/flat/20120803145635.GE9683%40tornado.leadboat.com

Gotcha, thanks for the clarification.

cheers ./daniel

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).