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Questions and Answers
What is the primary goal of process synchronization in a system?
To avoid race conditions and ensure consistency of shared data
What happens when access to shared data is not controlled?
A race condition exists, possibly resulting in corrupt data values.
What is a critical section in the context of process synchronization?
A section of code that accesses shared data and must be protected from concurrent access.
What is the purpose of hardware support for synchronization?
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What is the consequence of incorrect use of synchronization tools?
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What is the definition of a race condition?
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What is the significance of the next available pid in the context of race conditions?
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What is the role of mutex locks in process synchronization?
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What is the purpose of semaphores in process synchronization?
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What is the significance of atomic operations in process synchronization?
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Study Notes
Process Synchronization
- A system consists of multiple threads running concurrently or in parallel, sharing user data and operating system data structures.
- Process synchronization involves using tools to control access to shared data and avoid race conditions.
Race Condition
- A race condition occurs when multiple processes access and manipulate shared data concurrently, and the outcome depends on the order of access.
- An example of a race condition is the assignment of process identifiers in a system without mutual exclusion.
Critical Section Problem
- The critical section problem arises when multiple processes need to access shared data, and it must be solved to prevent race conditions.
- A solution to the critical section problem is necessary to ensure that only one process can access shared data at a time.
Mutex Locks
- Mutex locks are used to protect critical sections and prevent race conditions.
- A mutex lock has a Boolean variable indicating whether the lock is available or not.
- If the lock is available, a call to acquire() succeeds, and the lock is then considered unavailable.
- A process that attempts to acquire an unavailable lock is blocked until the lock is released.
- Calls to acquire() or release() must be performed atomically.
Disadvantages of Mutex Locks
- Implementing mutex locks requires busy waiting, where a process waiting for a lock continuously loops until the lock is released.
- Spinlocks are used to achieve short-duration locks, and they are preferred in certain circumstances on multicore systems.
Semaphores
- A semaphore is an integer variable accessed only through two standard atomic operations: signal() and wait().
- All modifications to the semaphore value must be executed atomically.
- There is a bound on the number of times other processes are allowed to enter their critical sections after a process has made a request to enter its critical section and before that request is granted.
Hardware Support for Synchronization
- Three major hardware instructions provide support for solving the critical-section problem.
- These primitive operations can be used directly as synchronization tools or to form the foundation of more abstract synchronization mechanisms.
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Description
Learn about process synchronization and its importance in preventing race conditions when multiple threads access shared data concurrently.
