CPSC 3220 - DAY 7
SEPTEMBER 19, 2017

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Threat threads as will be executed eventually.

Threads must be designed to work with any schedule.

thread_create(thread, func, args)

	-create a new thread to run function

thread_yield()

	-relinquish processor voluntarily

thread_join(thread)

	-in parent, wait for forked thread to exit, then return

thread_exit(return_value)

	-quit thread and clean up, wake up joiner if any.

Thread Context Switch

Voluntary:

	-Thread_yield()
	-Thread_join()

Involuntary:

	-Interrupt or exception
	-Other thread with higher priority

Fork/Join Concurrency

	-Threads can create children, and wait for their completion
	-Data only shared before fork/after join
		-Otherwise, extra code to coordinate access
	-Examples:
		-Web server: fork new thread for each new connection
			-As long as the threads are completely independent
		-Merge sort
		-Parallel memory copy

Threads at User and Kernel Level

	-Multiple single-threaded processes
		-System calls access shared kernel data structures
	-Multiple multi-threaded user processes
		-Each with multiple threads, sharing same data structures,
		isolated from other user processes
	-Kernel design
		-kernel can have zero threads (e.g., IBM MVT)
		-Kernel can use internal threads
		-in general, interrupt handlers are not threads can be used
		to wake or signal threads.