Re: [PATCH v6 0/5] MR3103: server: Create and use a desktop shared mapping for GetCursorPos.

[Torge Matthies (＠tmatthies)]

Torge Matthies (@tmatthies) commented about dlls/win32u/ntuser_private.h:
> BOOL is_window( HWND hwnd ) DECLSPEC_HIDDEN;
>
> +#if defined(__i386__) || defined(__x86_64__)
> +#define __SHARED_READ_SEQ( x )  (x)
> +#define __SHARED_READ_FENCE     do {} while(0)
> +#else
> +#define __SHARED_READ_SEQ( x )  __atomic_load_n( &(x), __ATOMIC_RELAXED )
> +#define __SHARED_READ_FENCE     __atomic_thread_fence( __ATOMIC_ACQUIRE )
> +#endif
> +
> +#define SHARED_READ_BEGIN( ptr, type )                                  \
> +    do {                                                                \
> +        const type *__shared = (ptr);                                   \
> +        unsigned int __seq;                                             \
> +        do {                                                            \
> +            while ((__seq = __SHARED_READ_SEQ( __shared->seq )) & 1) NtYieldExecution(); \
> I think this `NtYieldExecution` should not be here, the lock is unlikely to be held for long enough to make a full `sched_yield` syscall worthwile.
            while ((__seq = __SHARED_READ_SEQ( __shared->seq )) & 1) \
                __asm__ __volatile__ ("":"+m"(__shared->seq)); \

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https://gitlab.winehq.org/wine/wine/-/merge_requests/3103#note_42067