*The Little Book of Semaphores* is a free (in both senses of the word) textbook that introduces the principles of synchronization for concurrent programming.

In most computer science curricula, synchronization is a module in an Operating Systems class. OS textbooks present a standard set of problems with a standard set of solutions, but most students don't get a good understanding of the material or the ability to solve similar problems.

The approach of this book is to identify patterns that are useful for a variety of synchronization problems and then show how they can be assembled into solutions. After each problem, the book offers a hint before showing a solution, giving students a better chance of discovering solutions on their own.

The book covers the classical problems, including "Readers-writers," "Producer-consumer", and "Dining Philosophers." In addition, it collects a number of not-so-classical problems, some written by the author and some by other teachers and textbook writers. Readers are invited to create and submit new problems.

Additional resources at Green Tea Press.

- Preface
- Introduction
- Synchronization
- Execution model
- Serialization with messages
- Non-determinism
- Shared variables
- Concurrent writes
- Concurrent updates
- Mutual exclusion with messages

- Semaphores
- Definition
- Syntax
- Why semaphores?

- Basic synchronization patterns
- Signaling
- Rendezvous
- Rendezvous hint
- Rendezvous solution
- Deadlock #1

- Mutex
- Mutual exclusion hint
- Mutual exclusion solution

- Multiplex
- Multiplex solution

- Barrier
- Barrier hint
- Barrier non-solution
- Deadlock #2
- Barrier solution
- Deadlock #3

- Reusable barrier
- Reusable barrier non-solution #1
- Reusable barrier problem #1
- Reusable barrier non-solution #2
- Reusable barrier hint
- Reusable barrier solution
- Preloaded turnstile
- Barrier objects

- Queue
- Queue hint
- Queue solution
- Exclusive queue hint
- Exclusive queue solution

- Fifo queue
- Fifo queue hint
- Fifo queue solution

- Classical synchronization problems
- Producer-consumer problem
- Producer-consumer hint
- Producer-consumer solution
- Deadlock #4
- Producer-consumer with a finite buffer
- Finite buffer producer-consumer hint
- Finite buffer producer-consumer solution

- Readers-writers problem
- Readers-writers hint
- Readers-writers solution
- Starvation
- No-starve readers-writers hint
- No-starve readers-writers solution
- Writer-priority readers-writers hint
- Writer-priority readers-writers solution

- No-starve mutex
- No-starve mutex hint
- No-starve mutex solution

- Dining philosophers
- Deadlock #5
- Dining philosophers hint #1
- Dining philosophers solution #1
- Dining philosopher's solution #2
- Tanenbaum's solution
- Starving Tanenbaums

- Cigarette smokers problem
- Deadlock #6
- Smokers problem hint
- Smoker problem solution
- Generalized Smokers Problem
- Generalized Smokers Problem Hint
- Generalized Smokers Problem Solution

- Producer-consumer problem
- Less classical synchronization problems
- The dining savages problem
- Dining Savages hint
- Dining Savages solution

- The barbershop problem
- Barbershop hint
- Barbershop solution

- Hilzer's Barbershop problem
- Hilzer's barbershop hint
- Hilzer's barbershop solution

- The Santa Claus problem
- Santa problem hint
- Santa problem solution

- Building H2O
- H2O hint
- H2O solution

- River crossing problem
- River crossing hint
- River crossing solution

- The roller coaster problem
- Roller Coaster hint
- Roller Coaster solution
- Multi-car Roller Coaster problem
- Multi-car Roller Coaster hint
- Multi-car Roller Coaster solution

- The dining savages problem
- Not-so-classical problems
- The search-insert-delete problem
- Search-Insert-Delete hint
- Search-Insert-Delete solution

- The unisex bathroom problem
- Unisex bathroom hint
- Unisex bathroom solution
- No-starve unisex bathroom problem
- No-starve unisex bathroom solution

- Baboon crossing problem
- The Modus Hall Problem
- Modus Hall problem hint
- Modus Hall problem solution

- The search-insert-delete problem
- Not remotely classical problems
- The sushi bar problem
- Sushi bar hint
- Sushi bar non-solution
- Sushi bar non-solution
- Sushi bar solution #1
- Sushi bar solution #2

- The child care problem
- Child care hint
- Child care non-solution
- Child care solution
- Extended child care problem
- Extended child care hint
- Extended child care solution

- The room party problem
- Room party hint
- Room party solution

- The Senate Bus problem
- Bus problem hint
- Bus problem solution #1
- Bus problem solution #2

- The Faneuil Hall problem
- Faneuil Hall Problem Hint
- Faneuil Hall problem solution
- Extended Faneuil Hall Problem Hint
- Extended Faneuil Hall problem solution

- Dining Hall problem
- Dining Hall problem hint
- Dining Hall problem solution
- Extended Dining Hall problem
- Extended Dining Hall problem hint
- Extended Dining Hall problem solution

- The sushi bar problem
- Synchronization in Python
- Mutex checker problem
- Mutex checker hint
- Mutex checker solution

- The coke machine problem
- Coke machine hint
- Coke machine solution

- Mutex checker problem
- Synchronization in C
- Mutual exclusion
- Parent code
- Child code
- Synchronization errors
- Mutual exclusion hint
- Mutual exclusion solution

- Make your own semaphores
- Semaphore implementation hint
- Semaphore implementation
- Semaphore implementation detail

- Mutual exclusion
- Cleaning up Python threads
- Semaphore methods
- Creating threads
- Handling keyboard interrupts

- Cleaning up POSIX threads
- Compiling Pthread code
- Creating threads
- Joining threads
- Semaphores

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