Implemented _CheckNotSysLevel.

include/winbase.h

@@ -1918,6 +1918,7 @@ VOID        WINAPI RestoreThunkLock(DWORD);
 void        WINAPI SetProcessDword(DWORD,INT,DWORD);
 VOID        WINAPI UnMapLS(DWORD);
 HFILE       WINAPI Win32HandleToDosFileHandle(HANDLE);
+VOID        WINAPI _CheckNotSysLevel(SYSLEVEL *lock);
 DWORD       WINAPI _ConfirmWin16Lock(void);
 DWORD       WINAPI _ConfirmSysLevel(SYSLEVEL*);
 VOID        WINAPI _EnterSysLevel(SYSLEVEL*);

scheduler/syslevel.c

@@ -145,7 +145,11 @@ DWORD WINAPI _ConfirmSysLevel(SYSLEVEL *lock)
  */
 VOID WINAPI _CheckNotSysLevel(SYSLEVEL *lock)
 {
-    FIXME("(%p)\n", lock);
+    if (lock && lock->crst.OwningThread == GetCurrentThreadId() && lock->crst.RecursionCount)
+    {
+        ERR( "Holding lock %p level %d\n", lock, lock->level );
+        DbgBreakPoint();
+    }
 }