[WIN32SS:ENG/NTUSER] Use shared locks for display list lookups (#9090)

- Use shared locks for the display device and PDEV lookup paths.
  These functions only walk existing lists and take references, while list updates
  and mode-switch paths still use exclusive locking.
  This avoids serializing read-only display queries unnecessarily.

- Use shared locks for other read-only NtUser calls.

win32ss/user/ntuser/menu.c

@@ -6315,7 +6315,7 @@ NtUserMenuItemFromPoint(
    int Ret = -1;
 
    TRACE("Enter NtUserMenuItemFromPoint\n");
-   UserEnterExclusive();
+   UserEnterShared();
 
    if (!(Menu = UserGetMenuObject(hMenu)))
    {

win32ss/user/ntuser/simplecall.c

@@ -61,7 +61,19 @@ NtUserCallNoParam(DWORD Routine)
     DWORD_PTR Result = 0;
 
     TRACE("Enter NtUserCallNoParam\n");
-    UserEnterExclusive();
+
+    /* Read-only routines only need a shared lock; the rest stay exclusive */
+    switch (Routine)
+    {
+        case NOPARAM_ROUTINE_GETMSESSAGEPOS:
+        case NOPARAM_ROUTINE_GETIMESHOWSTATUS:
+        case NOPARAM_ROUTINE_ISCONSOLEMODE:
+            UserEnterShared();
+            break;
+        default:
+            UserEnterExclusive();
+            break;
+    }
 
     switch (Routine)
     {
@@ -158,7 +170,22 @@ NtUserCallOneParam(
 
     TRACE("Enter NtUserCallOneParam\n");
 
-    UserEnterExclusive();
+    /* Read-only routines only need a shared lock; the rest stay exclusive */
+    switch (Routine)
+    {
+        case ONEPARAM_ROUTINE_GETDESKTOPMAPPING:
+        case ONEPARAM_ROUTINE_WINDOWFROMDC:
+        case ONEPARAM_ROUTINE_GETKEYBOARDTYPE:
+        case ONEPARAM_ROUTINE_GETKEYBOARDLAYOUT:
+        case ONEPARAM_ROUTINE_ENUMCLIPBOARDFORMATS:
+        case ONEPARAM_ROUTINE_GETCURSORPOS:
+        case ONEPARAM_ROUTINE_GETPROCDEFLAYOUT:
+            UserEnterShared();
+            break;
+        default:
+            UserEnterExclusive();
+            break;
+    }
 
     switch (Routine)
     {
@@ -319,7 +346,6 @@ NtUserCallOneParam(
         }
 
         case ONEPARAM_ROUTINE_ENUMCLIPBOARDFORMATS:
-            /* FIXME: Should use UserEnterShared */
             Result = UserEnumClipboardFormats(Param);
             break;
 

win32ss/user/ntuser/window.c

@@ -1527,7 +1527,7 @@ NtUserBuildHwndList(
    if (pcHwndNeeded == NULL)
        return STATUS_INVALID_PARAMETER;
 
-   UserEnterExclusive();
+   UserEnterShared();
 
    if (hwndParent || !dwThreadId)
    {

win32ss/user/ntuser/winpos.c

@@ -3283,7 +3283,7 @@ NtUserChildWindowFromPointEx(HWND hwndParent,
 {
    PWND pwndParent;
    TRACE("Enter NtUserChildWindowFromPointEx\n");
-   UserEnterExclusive();
+   UserEnterShared();
    if ((pwndParent = UserGetWindowObject(hwndParent)))
    {
       pwndParent = IntChildWindowFromPointEx(pwndParent, x, y, uiFlags);