Re: [PATCH v21 0/9] MR3103: server: Create and use a desktop shared mapping for GetCursorPos.

[Jinoh Kang (＠iamahuman)]

Jinoh Kang (@iamahuman) commented about dlls/win32u/winstation.c:
> - const session_shm_t *shared;
>
> +};
> -
>
> +/* acquire a weak reference on a session */
> +static void shared_session_acquire_weak( struct shared_session *session )
> +{
> - int ref = InterlockedIncrement( &session->weak_ref );
> - TRACE( "session %p incrementing weak_ref to %d\n", session, ref );
>
> +}
> -
>
> +/* try acquiring a strong reference from a possibly weak referenced session */
> +static struct shared_session *shared_session_acquire( struct shared_session *session )
> +{
> - if (InterlockedOr( &session->ref, 0 ))
> - {
> -
>    int ref = InterlockedIncrement( &session->ref );

It looks like we have a race: another thread may invalidate `shared_session` just before here. Is it true?

* In that case, consulting `dlls/combase/marshal.c:proxy_manager_addref_if_alive()` might be a help.

* Otherwise, please explain (in comments) how it's not possible for `ref` to concurrently drop to zero.