Horton

Re: EINTR in ftruncate()

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-07-06T21:05:27Z
Lists: pgsql-hackers 
On Thu, Jul 7, 2022 at 9:03 AM Andres Freund <andres@anarazel.de> wrote:
> On 2022-07-07 08:56:33 +1200, Thomas Munro wrote:
> > On Thu, Jul 7, 2022 at 8:39 AM Andres Freund <andres@anarazel.de> wrote:
> > > So I think we need: 1) block most signals, 2) a retry loop *without*
> > > interrupt checks.
> >
> > Yeah.  I was also wondering about wrapping the whole function in
> > PG_SETMASK(&BlockSig), PG_SETMASK(&UnBlockSig), but also leaving the
> > while (rc == EINTR) loop there (without the check for *Pending
> > variables), only because otherwise when you attach a debugger and
> > continue you'll get a spurious EINTR and it'll interfere with program
> > execution.  All blockable signals would be blocked *except* SIGQUIT,
> > which means that fast shutdown/crash will still work.  It seems nice
> > to leave that way to interrupt it without resorting to SIGKILL.
>
> Fast shutdown shouldn't use SIGQUIT - did you mean immediate? I think
> it's fine to allow immediate shutdowns, but I don't think we should
> allow fast shutdowns to interrupt it.

Err, yeah, that one.

Commits

  1. Provide sigaction() for Windows.

  2. Emulate sigprocmask(), not sigsetmask(), on Windows.

  3. Make dsm_impl_posix_resize more future-proof.

  4. Don't clobber postmaster sigmask in dsm_impl_resize.

  5. Create a distinct wait event for POSIX DSM allocation.

  6. Remove redundant ftruncate() for POSIX DSM memory.

  7. Block signals while allocating DSM memory.

  8. Remove dsm_resize() and dsm_remap().

  9. XLOG (also known as WAL -:)) Bootstrap/Startup/Shutdown.