How do I program a critical section for read-write systems?

Let's say I have a read-write system in which a reader and a writer work at the same time. "a" and "b" are two shared variables that are related to each other, so modifying them should be an atomic operation.

The read-write system can be of the following types:

• rr
• Ww
• g-w
• g-ww
• p-p-f
• r-r-zhv

where
[r: single reader
rr: multiple reader
w: single writer
ww: multiple writer]

We can now have a reader for the reader and a writer for the writer as follows. I wrote them system type wise.

• rr

  read_method
  { read a; read b; }
  
        
  
          
          
          
        
  
      

• ww

  write_method
  { lock(m); write a; write b; unlock(m); }
  
        
  
          
          
          
        
  
      

• g-w

• g-ww
• p-p-f

• r-r-ww

  read_method
  { lock(m); read a; read b; unlock(m); }
  
  write_method
  { lock(m); write a; write b; unlock(m); }
  
        
  
          
          
          
        
  
      

For a system with multiple readers, access to a shared variable does not have to be atomic.

For a multiple notation system, shared access to a variable must be atomic, so locked with "m".

But for system types 3-6, is my read_method and write_method correct? How can I improve?

Best regards,
Srinivas Nayak