zephyr

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Keith Packard 0b90fd5adf samples, tests, boards: Switch main return type from void to int As both C and C++ standards require applications running under an OS to return 'int', adapt that for Zephyr to align with those standard. This also eliminates errors when building with clang when not using -ffreestanding, and reduces the need for compiler flags to silence warnings for both clang and gcc. Most of these changes were automated using coccinelle with the following script: @@ @@ - void + int main(...) { ... - return; + return 0; ... } Approximately 40 files had to be edited by hand as coccinelle was unable to fix them. Signed-off-by: Keith Packard <keithp@keithp.com>		2023-04-14 07:49:41 +09:00
..
src	samples, tests, boards: Switch main return type from void to int	2023-04-14 07:49:41 +09:00
CMakeLists.txt
prj.conf
README.rst
sample.yaml

README.rst

.. _samples_kernel_condvar:

Condition Variables
###################

Overview
********

This sample demonstrates the usage of condition variables in a
multithreaded application. Condition variables are used with a mutex
to signal changing states (conditions) from one thread to another
thread. A thread uses a condition variable to wait for a condition to
become true. Different threads alternate between their entry point
function execution based on when they signal the other thread that is
pending on the condition variable. The sample can be used with any
:ref:`supported board <boards>` and prints the sample output shown to
the console.

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

This application can be built and executed on Native Posix as follows:

.. zephyr-app-commands::
   :zephyr-app: samples/kernel/condition_variables/condvar
   :host-os: unix
   :board: native_posix
   :goals: run
   :compact:

To build for another board, change "native_posix" above to that board's name.

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

.. code-block:: console

    Starting watch_count: thread 1
    watch_count: thread 1 Count= 0. Going into wait...
    inc_count: thread 2, count = 1, unlocking mutex
    inc_count: thread 3, count = 2, unlocking mutex
    inc_count: thread 2, count = 3, unlocking mutex
    inc_count: thread 3, count = 4, unlocking mutex
    inc_count: thread 2, count = 5, unlocking mutex
    inc_count: thread 3, count = 6, unlocking mutex
    inc_count: thread 2, count = 7, unlocking mutex
    inc_count: thread 3, count = 8, unlocking mutex
    inc_count: thread 2, count = 9, unlocking mutex
    inc_count: thread 3, count = 10, unlocking mutex
    inc_count: thread 2, count = 11, unlocking mutex
    inc_count: thread 3, count = 12  Threshold reached.Just sent signal.
    inc_count: thread 3, count = 12, unlocking mutex
    watch_count: thread 1 Condition signal received. Count= 12
    watch_count: thread 1 Updating the value of count...
    watch_count: thread 1 count now = 137.
    watch_count: thread 1 Unlocking mutex.
    inc_count: thread 2, count = 138, unlocking mutex
    inc_count: thread 3, count = 139, unlocking mutex
    inc_count: thread 2, count = 140, unlocking mutex
    inc_count: thread 3, count = 141, unlocking mutex
    inc_count: thread 2, count = 142, unlocking mutex
    inc_count: thread 3, count = 143, unlocking mutex
    inc_count: thread 2, count = 144, unlocking mutex
    inc_count: thread 3, count = 145, unlocking mutex
    Main(): Waited and joined with 3 threads. Final value of count = 145. Done.