Deadlocks: The deadlock denotes a situation where a collection of threads remains blocked. It denotes waiting for a condition that will never be true. The progress graph denotes invaluable tool for understanding deadlock. If “P” and “V” operations are been ordered incorrectly, the forbidden regions for two semaphores would overlap. If some execution trajectory reaches deadlock state “d” then no further progress is possible. In this case each thread waits for the other one for a “V” operation that never occurs. The overlapping forbidden regions would induce a set of states called “deadlock region”. The deadlock is inevitable is trajectory touches a state in deadlock region. Once it enters deadlock regions, the trajectories could never leave. Mutex lock ordering rule: A program is deadlock-free if each thread acquires its mutexes in order. It releases them in reverse order and given a total ordering for all mutexes. The mutex should be achieved in order to ensure deadlock free scheme.

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Chapter 12, Problem 12.29HW

Program Plan Intro

Deadlocks:

The deadlock denotes a situation where a collection of threads remains blocked.

It denotes waiting for a condition that will never be true.

The progress graph denotes invaluable tool for understanding deadlock.

If “P” and “V” operations are been ordered incorrectly, the forbidden regions for two semaphores would overlap.

If some execution trajectory reaches deadlock state “d” then no further progress is possible.

In this case each thread waits for the other one for a “V” operation that never occurs.

The overlapping forbidden regions would induce a set of states called “deadlock region”.

The deadlock is inevitable is trajectory touches a state in deadlock region.

Once it enters deadlock regions, the trajectories could never leave.

Mutex lock ordering rule:

A program is deadlock-free if each thread acquires its mutexes in order.

It releases them in reverse order and given a total ordering for all mutexes.

The mutex should be achieved in order to ensure deadlock free scheme.

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