Niall Cooling (@NiallCooling)

Niall Cooling is a Chartered Engineer and Founder of Feabhas, the UK’s leading independent provider of training and consultancy for real-time embedded systems development and software competency. Niall delivers training and provides consultancy and mentoring to a wide variety of electronics companies ranging from smart metering, industrial control, telecommunications and defence. He is also a regular guest speaker at industry conferences and events throughout the world and has particular interest in establishing a competency framework for Embedded Software Engineering.

Mutex vs. Semaphores – Part 2: The Mutex & Mutual Exclusion Problems

Niall Cooling ● May 15, 2019●7 comments

Part 1 of this series we looked at the history of the binary and counting semaphore, and then went on to discuss some of the associated problem areas. In this posting I aim to show how a different RTOS construct, the mutex, may overcome some, if not all, of these weaknesses.

To address the problems associated with semaphore, a new concept was developed during the late 1980’s. I have struggled to find it’s first clear definition, but the major use of the term mutex (another...

Mutex vs. Semaphore - Part 1

Niall Cooling ● April 12, 2019●5 comments

It never ceases to amaze me how often I see postings in forums asking the difference between a semaphore and a mutex. Probably what baffles me more is that over 90% of the time the responses given are either incorrect or missing the key differences. The most often quoted response is that of the “The Toilet Example (c) Copyright 2005, Niclas Winquist” . This summarises the differences as:

• A mutex is really a semaphore with value 1

No, no, and no again....

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