Monthly Archives: September 2009

Mutex vs. Semaphores – Part 2: The Mutex

In 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 […]

Posted in RTOS | Tagged , , , | 17 Comments

Mutex vs. Semaphores – Part 1: Semaphores

It never ceases to amaze me how often I see postings in newsgroups, etc. 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 […]

Posted in RTOS | Tagged , , , | 29 Comments

Getting started is always the hardest thing…

I’ve been procrastinating for the best part of a couple of months now getting this blog started. First of all I do feel a little late to the party, has blogging been surpassed by tweeting? Strangely I’ve actually been using twitter in anger since late march (@feabhas) and I’ll cover my experiences of that in a later post.So what is the aim of this blog? My hope is to cover, in a no-nonsense manner, aspects centered on Real-Time and Embedded […]

Posted in General | 5 Comments