LKMPG/older_versions/4.9.11/examples/example_rwlock.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/interrupt.h>

DEFINE_RWLOCK(myrwlock);

static void example_read_lock(void)
{
    unsigned long flags;

    read_lock_irqsave(&myrwlock, flags);
    printk("Read Locked\n");

    /* Read from something */

    read_unlock_irqrestore(&myrwlock, flags);
    printk("Read Unlocked\n");
}

static void example_write_lock(void)
{
    unsigned long flags;

    write_lock_irqsave(&myrwlock, flags);
    printk("Write Locked\n");

    /* Write to something */

    write_unlock_irqrestore(&myrwlock, flags);
    printk("Write Unlocked\n");
}

static int example_rwlock_init(void)
{
    printk("example_rwlock started\n");

    example_read_lock();
    example_write_lock();

    return 0;
}

static void example_rwlock_exit(void)
{
    printk("example_rwlock exit\n");
}

module_init(example_rwlock_init);
module_exit(example_rwlock_exit);

MODULE_AUTHOR("Bob Mottram");
MODULE_DESCRIPTION("Read/Write locks example");
MODULE_LICENSE("GPL");