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Process Synchronization & Race Condition

  
    ⇰  SYNCHRONIZATION :-

 Process Synchronization is simply a way to coordinate processes that share something or use shared data. Synchronization occurs in an operating system among cooperating processes. Before starting the brief discuss we have to know types of processes.
  There are two types of process according to sharing :-
i>  Independent process.
ii> Coordinate process.

 i>  Independent process :- Those process which do not share anything to other processes is called Independent process. Execution of one process will not affect other process.

ii> Coordinate process :- Those process which share something with other processes as common variable, memory, code or resources(cpu, printer). So execution of a particular process can affect other process. And cooperative process is not properly synchronised, that can create problem as data inconsistancy.

  While executing many cooperative processes, process synchronization helps to maintain shared data consistency and cooperating process execution. Processes have to be synchronized to ensure that concurrent access to shared data or anything does not create inconsistency. Let us see a problem:-
 Consider two peocesses P1 and P2 running on some system at same time. Let there is a common variable 'shared'.
sleep(1) :- This code is used to switch Between processes.

Execution of Processes will bs as follows:- 
Hence shared=4, which is wrong because in execution of P1 & P2, X++ and Y-- emplies the same as 5++ =>6 and 6-- => 5. 
This situation arrised because P1 & P2 are not synchronized.
      ⇰  RACE CONDITION :-

 When data is not consistent the situation is called race condition. A race condition occurs when two or more porcesses execute at the same time, without synchronized in the proper sequence. As we can see in our above example when we start execution of P1 first than P2, we get shared=4 and id we start P2 first than P1 we get shared-6. But both are wrong because shared must equal to 5.

    The situation like this, where several processes access and manipulate the same data concurrently and outcome of the execution depends upon particular order in which access takes place is called as race condition. 

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