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pid waitstatus else child exitstatus the

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Unformatted text preview: fork()) { /* parent */ ….. pid = wait(&status); } else { /* child */ ….. exit(status); } The fork syscall returns twice: it returns a zero to the child and the child process ID (pid) to the parent. Parent uses wait to sleep until the child exits; wait returns child pid and status. Wait variants allow wait on a child, or notification of stops and other signals. Process Process States CSci CSci 5103 Operating Systems Threads Threads: Threads: What are they? A thread is a basic unit of CPU utilization or execution defined by CPU register values (PC, SP) each thread must have its own stack suspend: suspend: save register values in memory resume: restore registers from memory Multiple threads can execute independently: They can run in parallel on multiple CPUs - physical concurrency … or arbitrarily interleaved on a single CPU - logical concurrency Threads Threads and Data Threads inside a process share state When When is data shared? • local variables are private: remember each thread gets its own own stack • global variables are shared • dynamic variabl...
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