Apologies for the confusion.

1. FCFS - First come first serve

2. Rewriting the example

Critical section= CS

Example:
Call1 to crit.pl - running CS
Call2 to crit.pl- waiting for lock on CS
Call3 to crit.pl- waiting for lock on CS
[download]

Lets say the CS writes timestamp entry to the file . Following events

Time1:Call1 is running CS, Call2 is waiting for acquiring lock on CS.

Time2: Call1 is still running, call 2 waiting for the lock on CS+ a new call3 is also waiting for the lock on CS

Time3 : call1 complete. Call2 acquires lock on CS. Call3 waits

Time4: call2 complete. Call3 acquires lock

Basically want the critical section to execute in the same order of call.

The order of time stamps in critical section should always be in ascending order . Hope this makes it clearer.