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Race conditions, Critical Sections and Semaphores are an key part of Operating systems. Details about these are given as follows −
A race condition is a situation that may occur inside a critical section. This happens when the result of multiple thread execution in critical section differs according to the order in which the threads execute.
Race conditions in critical sections can be avoided if the critical section is treated as an atomic instruction. Also, proper thread synchronization using locks or atomic variables can prevent race conditions.
The critical section in a code segment where the shared variables can be accessed. Atomic action is required in a critical section i.e. only one process can execute in its critical section at a time. All the other processes have to wait to execute in their critical sections.
In the above diagram, the entry sections handles the entry into the critical section. It acquires the resources needed for execution by the process. The exit section handles the exit from the critical section. It releases the resources and also informs the other processes that critical section is free.
The critical section problem needs a solution to synchronise the different processes. The solution to the critical section problem must satisfy the following conditions −
A semaphore is a signalling mechanism and a thread that is waiting on a semaphore can be signalled by another thread. This is different than a mutex as the mutex can be signalled only by the thread that called the wait function.
A semaphore uses two atomic operations, wait and signal for process synchronization.
The wait operation decrements the value of its argument S, if it is positive. If S is negative or zero, then no operation is performed.
The signal operation increments the value of its argument S.
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Now, let's delve into the concepts outlined in the provided article: "Race conditions, Critical Sections, and Semaphores."
Race Conditions: A race condition in the context of operating systems refers to a scenario within a critical section where the outcome of multiple thread executions differs based on the order in which the threads execute. To mitigate race conditions in critical sections, treating the critical section as an atomic instruction is essential. This ensures that only one process can execute in the critical section at any given time. Proper thread synchronization mechanisms, such as locks or atomic variables, play a crucial role in preventing race conditions.
Critical Sections: A critical section is a code segment where shared variables can be accessed. An atomic action is required within a critical section, meaning that only one process can execute within it at a time. Other processes must wait for their turn to execute in their respective critical sections. The diagram provided illustrates entry and exit sections: entry handles resource acquisition, while exit manages resource release and informs other processes about the critical section's availability.
Semaphores: Semaphores serve as signaling mechanisms in process synchronization. Unlike mutexes, a thread waiting on a semaphore can be signaled by another thread. Semaphores rely on two atomic operations: wait and signal. The wait operation decrements the value of the semaphore, but only if it's positive. If the value is zero or negative, no operation is performed. On the other hand, the signal operation increments the semaphore's value.
In summary, understanding and effectively implementing concepts like race conditions, critical sections, and semaphores are fundamental in ensuring the smooth and synchronized operation of concurrent processes within an operating system. These concepts form the backbone of robust and efficient system design and are integral to the field of computer science.
