zephyr

History

Andrew Boie feab37096b libc: fix CONFIG_STDOUT_CONSOLE semantics The intent of this Kconfig is to allow libc stdout functions like printf() to send their output to the active console driver instead of discarding it. This somehow evolved into preferring to use printf() instead of printk() for all test case output if enabled. Libc printf() implementation for both minimal libc and newlib use considerably more stack space than printk(), with nothing gained by using them. Remove all instances where we are conditionally sending test case output based on this config, enable it by default, and adjust a few tests that disabled this because they were blowing stack. printk() and vprintk() now work as expected for unit_testing targets, they are just wrappers for host printf(). Fixes: #13701 Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>		2019-02-26 08:00:33 -06:00
..
src	libc: fix CONFIG_STDOUT_CONSOLE semantics	2019-02-26 08:00:33 -06:00
CMakeLists.txt	cmake: increase minimal required version to 3.13.1	2019-01-03 11:51:29 -05:00
README.rst	doc: getting_started: Support multi-OS instructions	2018-01-18 16:53:31 -05:00
prj.conf	tests/sched/scheduler_api: samples/philosophers: Use SCHED_SCALABLE	2018-07-03 17:09:15 -04:00
prj_tickless.conf	kernel: ensure System Power Managment enables Tickless Idle.	2018-11-21 23:16:35 -05:00
sample.yaml	tests/samples: cleanup tags	2018-10-16 09:17:51 -04:00

README.rst

.. _dining-philosophers-sample:

Dining Philosophers
###################

Overview
********

An implementation of a solution to the Dining Philosophers problem (a classic
multi-thread synchronization problem).  This particular implementation
demonstrates the usage of multiple preemptible and cooperative threads of
differing priorities, as well as dynamic mutexes and thread sleeping.

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.

It is possible to run the demo in coop-only or preempt-only mode. To achieve
this, set these values for CONFIG_NUM_COOP_PRIORITIES and
CONFIG_NUM_PREEMPT_PRIORITIES in prj.conf:

preempt-only:

  CONFIG_NUM_PREEMPT_PRIORITIES 6
  CONFIG_NUM_COOP_PRIORITIES 0

coop-only:

  CONFIG_NUM_PREEMPT_PRIORITIES 0
  CONFIG_NUM_COOP_PRIORITIES 6

In these cases, the philosopher threads will run with priorities 0 to 5
(preempt-only) and -7 to -2 (coop-only).

Building and Running
********************

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

.. zephyr-app-commands::
   :zephyr-app: samples/philosophers
   :host-os: unix
   :board: qemu_x86
   :goals: run
   :compact:

Sample Output
=============

.. code-block:: console

   Philosopher 0 [P: 3]  HOLDING ONE FORK
   Philosopher 1 [P: 2]  HOLDING ONE FORK
   Philosopher 2 [P: 1]  EATING  [ 1900 ms ]
   Philosopher 3 [P: 0]  THINKING [ 2500 ms ]
   Philosopher 4 [C:-1]  THINKING [ 2200 ms ]
   Philosopher 5 [C:-2]  THINKING [ 1700 ms ]