typedef struct _EX_PUSH_LOCK_WAIT_BLOCK
{
     union
     {
          KGATE WakeGate;
          KEVENT WakeEvent;
     };
     PEX_PUSH_LOCK_WAIT_BLOCK Next;
     PEX_PUSH_LOCK_WAIT_BLOCK Last;
     PEX_PUSH_LOCK_WAIT_BLOCK Previous;
     LONG ShareCount;
     LONG Flags;
} EX_PUSH_LOCK_WAIT_BLOCK, *PEX_PUSH_LOCK_WAIT_BLOCK;

Windows Vista Kernel Structures