Horton

Re: [PATCH] Add native windows on arm64 support

Dave Cramer <davecramer@postgres.rocks>

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From: Dave Cramer <davecramer@postgres.rocks>
To: Andres Freund <andres@anarazel.de>
Cc: Andrew Dunstan <andrew@dunslane.net>, Michael Paquier <michael@paquier.xyz>, Anthony Roberts <anthony.roberts@linaro.org>, Daniel Gustafsson <daniel@yesql.se>, Lina Iyer <lina.iyer@linaro.org>, Mike Holmes <mike.holmes@linaro.org>, Peter Eisentraut <peter@eisentraut.org>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Thomas Munro <thomas.munro@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2024-02-13T17:49:33Z
Lists: pgsql-hackers 
Dave Cramer
www.postgres.rocks


On Mon, 12 Feb 2024 at 16:19, Andres Freund <andres@anarazel.de> wrote:

> Hi,
>
> On 2024-02-12 12:50:12 -0800, Andres Freund wrote:
> > On 2024-02-12 13:28:40 -0500, Andrew Dunstan wrote:
> > I wonder if this indicates that we are either missing memory barriers
> > somewhere or that the memory barriers we end up with on msvc + arm aren't
> > correct?  Either could explain why the problem doesn't occur when
> building
> > with optimizations.
>
> I think I might have been on to something - if my human emulation of a
> preprocessor isn't wrong, we'd end up with
>
> #define S_UNLOCK(lock)  \
>         do { _ReadWriteBarrier(); (*(lock)) = 0; } while (0)
>
> on msvc + arm. And that's entirely insufficient - _ReadWriteBarrier() just
> limits *compiler* level reordering, not CPU level reordering.  I think it's
> even insufficient on x86[-64], but it's definitely insufficient on arm.
>
In fact ReadWriteBarrier has been deprecated _ReadWriteBarrier | Microsoft
Learn
<https://learn.microsoft.com/en-us/cpp/intrinsics/readwritebarrier?view=msvc-170>

I did try using atomic_thread_fence as per atomic_thread_fence -
cppreference.com
<https://en.cppreference.com/w/c/atomic/atomic_thread_fence>


However for some reason including #include <stdatomic.h>
causes a bunch of compiler errors.

c:\Program Files\Microsoft Visual
Studio\2022\Community\VC\Tools\MSVC\14.38.33130\include\vcruntime_c11_stdatomic.h(36):
error C2061: syntax error: identifier 'atomic_bool'

Dave