Horton

Re: EINTR in ftruncate()

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Pg Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-07-14T14:46:52Z
Lists: pgsql-hackers 
On 2022-Jul-15, Thomas Munro wrote:

> I checked that this throw-away assertion doesn't fail currently:
> 
>         if (IsUnderPostmaster)
> +       {
> +               sigset_t old;
> +               sigprocmask(SIG_SETMASK, NULL, &old);
> +               Assert(memcmp(&old, &UnBlockSig, sizeof(UnBlockSig)) == 0);
>                 PG_SETMASK(&BlockSig);
> +       }
> 
> ... but now I'm wondering if we should be more defensive and possibly
> even save/restore the mask.

Yeah, that sounds better to me.

> Originally I discounted that because I thought I had to go through
> PG_SETMASK for portability reasons, but on closer inspection, I don't
> see any reason not to use sigprocmask directly in Unix-only code.

ISTM it would be cleaner to patch PG_SETMASK to have a second argument
and to return the original mask if that's not NULL.  This is more
invasive, but there aren't that many callsites of that macro.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/

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.