Sleep

Depends on	Scheduler • Process States

Note: this article is about a process becoming blocked for a while on a timer. It is different from the process-synchronisation “sleep”.

“Sleep” is a Unix name for a process suspended (blocked) waiting for a time.

Experiment: try: “sleep 5; echo Wake up.” in a Unix shell.

Any number (within reason!) of processes may be sleeping at the same time. As there is not ‘any number’ of hardware clocks available, it is likely that all sleeping processes will be queued, sorted chronologically and rescheduled (unblocked) by a timer interrupt.

Inside a C program, the library call sleep(<seconds>) will provide the appropriate system call.

Exercise: write a little application which prints output at a human-readable rate using sleep() calls to regulate progress. (There are some ‘hints’ in file_input.c, but try and do without.)

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Context Dependencies Dependants

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Articles on Processes

About this resource • Atomicity • Containers • Context • Context Switching • Daemons • Fork Unix • Hypervisor • Idle • Interprocess Communication • Multi Threading • Mutual exclusion • Pipes • Pointer Arithmetic • Process Control Block (PCB) • Process Priority • Process Scheduling • Process States • Processes • Queues • Queues Extra • Race Conditions • Real Time • Resources • Scheduler • Signal and Wait • Sleep • Starvation • Synchronisation • Thrashing • Threads • Unix Signals