Processes Synchronization - Part I

• The text discusses solutions to the Critical-Section Problem, where multiple processes need to access shared resources without conflicts.
• The problem involves n processes, each with a Critical Section (CS) where common variables are changed, tables updated, or files written.
• Only one process can be in its CS at a time; others must wait.
• The CS is preceded by an entry section and followed by an exit section, forming the general structure of a process.
• Three requirements for CS solutions: mutual exclusion, progress, and bounded waiting.
• Peterson's solution uses two shared variables, a boolean flag "turn" and a flag indicating readiness to enter the CS.
• In the algorithm for Process Pi, mutual exclusion is ensured by only allowing entry if flag[j] is false or turn equals i.
• Peterson's solution provides proof that the three requirements are met when accessing shared resources.
• Mutex locks protect a CS by first acquiring a lock and releasing it.
• Mutex locks are implemented using a Boolean variable and atomic operations.
• pthread mutexes are another solution, where a mutex is represented by the pthread mutex object.
• Semaphores provide more sophisticated synchronization methods for processes with an integer variable and atomic wait() and signal() operations.
• Deadlock and starvation are potential issues with semaphores.
• POSIX semaphores can be created, waited on, and posted using sem_open(), sem_wait(), and sem_post().
• Parent-child example uses semaphores for synchronization between parent and child processes.
• Readers and Writers problem deals with allowing multiple readers to read a shared data set simultaneously while ensuring only one writer can access it at a given time.
• The solution involves using a shared data semaphore, reader mutex, and writer mutex, as well as an integer read count, ensuring mutual exclusion, progress, and bounded waiting.

Learn about processes synchronization, concurrent access to shared data, and maintaining data consistency through mechanisms to ensure orderly execution of cooperating processes. This quiz covers topics such as the producer-consumer problem and data inconsistency.