DEBUG_LOCKS_WARN_ON(lock->owner != current)

mutex_master.c

#include <linux/module.h>
#include <linux/init.h>

#include <linux/mutex.h>

DEFINE_MUTEX (master_mutex);
EXPORT_SYMBOL(master_mutex);

static int __init mutex_master_init(void)
{
        pr_info("%s loading at 0x%p\n", KBUILD_MODNAME, mutex_master_init);
        return 0;
}

static void __exit mutex_master_exit(void)
{
        pr_info("%s is been unloaded\n", KBUILD_MODNAME);
}

module_init(mutex_master_init);
module_exit(mutex_master_exit);

MODULE_AUTHOR("Pedro Duarte");
MODULE_LICENSE("GPL v2");

mutex_slave_one.c

#include <linux/module.h>
#include <linux/init.h>

#include <linux/mutex.h>

extern struct mutex master_mutex;

static int __init mutex_slave_one_init(void)
{
        pr_info("%s loading at 0x%p\n", KBUILD_MODNAME, mutex_slave_one_init);

        if (mutex_trylock(&master_mutex))
                return 0;

        return -EBUSY;
}

static void __exit mutex_slave_one_exit(void)
{
        mutex_unlock(&master_mutex);
        pr_info("%s is been unloaded\n", KBUILD_MODNAME);
}

module_init(mutex_slave_one_init);
module_exit(mutex_slave_one_exit);

MODULE_AUTHOR("Pedro Duarte");
MODULE_LICENSE("GPL v2");

mutex_slave_two.c

#include <linux/module.h>
#include <linux/init.h>

#include <linux/mutex.h>

extern struct mutex master_mutex;

static int __init mutex_slave_two_init(void)
{
        pr_info("%s loading at 0x%p\n", KBUILD_MODNAME, mutex_slave_two_init);

        if (mutex_trylock(&master_mutex))
                return 0;

        return -EBUSY;
}

static void __exit mutex_slave_two_exit(void)
{
        mutex_unlock(&master_mutex);
        pr_info("%s is been unloaded\n", KBUILD_MODNAME);
}

module_init(mutex_slave_two_init);
module_exit(mutex_slave_two_exit);

MODULE_AUTHOR("Pedro Duarte");
MODULE_LICENSE("GPL v2");