Are database locks reentrant?

Hi,

I'm using sql server profiler to investigate a deadlock and want to see if I'm interpreting the mode column of the Lock:Acquired and Lock:Released events correctly.

Here is a sequence of lock events on one of the resources involved in the deadlock.

EventClass, TextData, SPID, Type, Mode

• Lock:Acquired, (91c240674a87), 71, 7 - Key, 4 - U
• Lock:Acquired, (91c240674a87), 71, 7 - Key, 5 - X
  
• Lock:Released, (91c240674a87), 71, 7 - Key, 0 - NULL
  

Event 2 - the update lock was converted to an exclusive lock.  Event 3 - process 71 no longer holds a lock on the key.  Is that correct?

What I want to rule out is the possibility that database locks are reentrant, and 2 successive lock events by the same process would require 2 release events to free the resource.

I'm using Sql Server 2008 r2.

David