Five years ago the textbook for my Operating Systems course, Operating Systems and Middleware: Supporting Controlled Interaction was published by Course Technology. It has been used at scattered universities and colleges around the world and even attracted a few fans, but it never caught on enough to be a commercial success. Last fall, Course Technology graciously assigned the copyright back to me so that I could give the text a new life with a revised edition.

In the revised edition, I made various improvements throughout, and also two more substantive changes: a totally replaced section to reflect a complete change in how Linux schedules tasks to run on processor cores, and a brand new section on the topic of nonblocking synchronization, which has become increasingly important. (Throughout the book, I found that updates were likely to reflect topics that already existed five years ago, but had now emerged from being esoteric research to being well-established practice, suitable for inclusion in an undergraduate text. It was less common for me to include something that was genuinely new.)

But the really dramatic change was in how the book is released. Instead of a commercial, hardbound book, it is available on the web under a Creative Commons license that not only permits free use, but also modification. I’m actively encouraging others to contribute to the further development of the text; for that reason, I’ve made modification practical (rather than merely legal) by releasing the source files from which the book is produced. Opening a book for modification rather than merely use is rare, so I’m waiting to see how it will pan out.