[carlehewitt]

Yes, conditional critical regions can be slower because conditions can be redundantly tested.

Below is an Actor implementation of a read priority solution to the readers writers problem:

  ReadPriority[aDatabase:*ReadersWriter*]:*ReadersWriterManager*
       //  Invariant: **Nonempty** #writing# ⇨ **IsEmpty** #reading#
   **Locals**(Queue(#writersQ#, #readersQ#),
              Crowd(#reading#),
              AtMostOne(#writing#)),
   **Handlers**( 
       ⟦scheduler⟧ ↦ **As** myScheduler, // myScheduler facet of this manager
       upgrade[newVersion] ↦ 
            (**CancellAll**  #readersQ# **and** #writersQ# **and** #reading# **and** #writing#
                  **for** **Become** newVersion)
   myScheduler **implements** *ReadersWriter* **Handlers**( 
      read[aQuery] ↦ 
         **Enqueue** #readersQ# **when** **Nonempty** #writing# **or** #writersQ# **or** #readersQ# 
             **for** aDatabase.read[aQuery] **thru** #reading#
                    **permit** #readersQ#
                       **afterward** **Permit** #writersQ# **when** **IsEmpty** #reading#
                                                **else** #readersQ# **when** **IsEmpty** #writersQ#,
      write[anUpdate] ↦    
         **Enqueue** #writersQ# **when** **Nonempty** #reading# **or** #readersQ# **or** #writing# **or** #writersQ#  
              **for** aDatabase.write[anUpdate] **thru** #writing#
                   **afterward** **Permit** #readersQ# **else** #writersQ#)▮