| From: | Dave Cramer <davecramer(at)postgres(dot)rocks> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Michael Paquier <michael(at)paquier(dot)xyz>, Anthony Roberts <anthony(dot)roberts(at)linaro(dot)org>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Lina Iyer <lina(dot)iyer(at)linaro(dot)org>, Mike Holmes <mike(dot)holmes(at)linaro(dot)org>, Peter Eisentraut <peter(at)eisentraut(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: [PATCH] Add native windows on arm64 support |
| Date: | 2024-02-13 17:49:33 |
| Message-ID: | CADK3HHKmzUZRqi-cPipPoV1=igM17cynfLW3aBwd-CkqK=PEkw@mail.gmail.com |
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Dave Cramer
www.postgres.rocks
On Mon, 12 Feb 2024 at 16:19, Andres Freund <andres(at)anarazel(dot)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
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