Dining Philosophers (CMSI RTOS V1 APIs)

Overview

This sample implements a solution to the Dining Philosophers problem (a classic multi-thread synchronization problem) using CMSIS RTOS V1 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 V1 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:

cd $ZEPHYR_BASE/samples/philosophers
mkdir build && cd build
cmake -GNinja -DBOARD=qemu_x86 ..
ninja run

Sample Output

Philosopher 0 [C:-2]  THINKING [  500 ms ]
Philosopher 1 [C:-1]  THINKING [  375 ms ]
Philosopher 2 [P: 0]  THINKING [  575 ms ]
Philosopher 3 [P: 1]   EATING  [  525 ms ]
Philosopher 4 [P: 2]  THINKING [  800 ms ]
Philosopher 5 [P: 3]   EATING  [  625 ms ]

Demo Description
----------------
An implementation of a solution to the Dining Philosophers
problem (a classic multi-thread synchronization problem) using
CMSIS RTOS V1 APIs. This particular implementation demonstrates the
usage of multiple preemptible threads of differing
priorities, as well as semaphores and thread sleeping.