Mutex not unlock ?

RE: Mutex not unlock ?

babos — Mon, 02 Jan 2023 14:44:02 GMT

Hi, Andreas.

Yes, it is clear and useful, thanks we can close the ticket. I understand.

best regards

RE: Mutex not unlock ?

AHaug — Mon, 02 Jan 2023 13:24:46 GMT

Hi,

You might've already seen this course, but I would recommend you to take a look at the fundamentals course we have at https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/. Topic 7 and topic 8 contains theory and hands on exercises (with solutions) about multithreaded applications and Thread synchronization. Topic 8, exercise 2 (with the solution here) even illustrates how to use mutexes to synchronize two threads that attempts to access the same code simultaneously.

The mentioned topics should give you a hint as for why your implementation might not behave as you expected. As far as I can see the first thread is run once at the beginning, but never again after line 24.

Let me know if the link is helpful and if you have more questions regarding this topic.

Kind regards,
Andreas

RE: Mutex not unlock ?

babos — Sat, 31 Dec 2022 13:45:35 GMT

or this:

/*
 * Copyright (c) 2012-2014 Wind River Systems, Inc.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <zephyr/kernel.h>

#define STACKSIZE (1024)
#define PRIORITY 5

K_MUTEX_DEFINE(m1);
K_MUTEX_DEFINE(m2);

/* work thread 1 */
void ping()
{
	while (true)
	{
		k_mutex_lock(&m1, K_FOREVER);
		printk("ping\n");
		k_mutex_unlock(&m2);
		k_busy_wait(100000);
		k_msleep(2000);
	}
}
/* work thread 2 */
void pong()
{
	while (true)
	{
		k_mutex_lock(&m2, K_FOREVER);
		printk("pong\n");
		k_mutex_unlock(&m1);
		k_busy_wait(100000);
		k_msleep(2000);
	}
}

void main(void)
{
	printk("WORK MUTEX on board: %s\n\n", CONFIG_BOARD);
	k_mutex_lock(&m1, K_FOREVER);
	k_mutex_unlock(&m2);
}

K_THREAD_DEFINE(thread_1_id, STACKSIZE, ping, NULL, NULL, NULL,
				PRIORITY, 0, 500);
K_THREAD_DEFINE(thread_2_id, STACKSIZE, pong, NULL, NULL, NULL,
				PRIORITY, 0, 500);