Re: [PATCH] Add native windows on arm64 support

On Tue, 13 Feb 2024 at 12:52, Andres Freund <andres@anarazel.de> wrote:

Hi,

On 2024-02-13 12:49:33 -0500, Dave Cramer wrote:
> > 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'd just ignore that, that's just pushing towards more modern stuff that's
more applicable to C++ than C.


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

The semantics of atomic_thread_fence are, uh, very odd.  I'd just use
MemoryBarrier().

#define S_UNLOCK(lock)  \

    do { MemoryBarrier(); (*(lock)) = 0; } while (0)

#endif

 

Has no effect.

I have no idea if that is what you meant that I should do ?

Dave