Dining Philosophers (CMSI RTOS V2 APIs)

Overview

This sample implements a solution to the Dining Philosophers problem (a classic multi-thread synchronization problem) using CMSIS RTOS V2 APIs. This particular implementation demonstrates the usage of multiple preemptible and cooperative threads of differing priorities, as well as mutex/semaphore and thread sleeping which uses CMSIS RTOS V2 API implementation in Zephyr.

The philosopher always tries to get the lowest fork first (f1 then f2). When done, he will give back the forks in the reverse order (f2 then f1). If he gets two forks, he is EATING. Otherwise, he is THINKING. Transitional states are shown as well, such as STARVING when the philosopher is hungry but the forks are not available, and HOLDING ONE FORK when a philosopher is waiting for the second fork to be available.

Each Philosopher will randomly alternate between the EATING and THINKING state.

Building and Running

This project outputs to the console. It can be built and executed on QEMU as follows:

Using west:

west build -t run

Using CMake and ninja:

cmake -B build -GNinja -DBOARD=qemu_x86 samples/philosophers
ninja -C build run

Sample Output

Philosopher 0 [P: 8]    HOLDING ONE FORK
Philosopher 1 [P: 9]    HOLDING ONE FORK
Philosopher 2 [P: 10]   EATING  [  575 ms ]
Philosopher 3 [P: 11]  THINKING [  225 ms ]
Philosopher 4 [P: 12]  THINKING [  425 ms ]
Philosopher 5 [P: 13]  THINKING [  325 ms ]

Demo Description
----------------
An implementation of a solution to the Dining Philosophers
problem (a classic multi-thread synchronization problem) using
CMSIS RTOS V2 APIs. This particular implementation demonstrates the
usage of multiple preemptible threads of differing
priorities, as well as semaphores and thread sleeping.