Linux Kernel（9）- Kthread

在kernel中建立thread可以使用kthread_create()，建立一個task，然後在調用wake_up_process(task)讓task真正的運行，如果要kill一個kthread可以使用kthread_stop()。
在kernel中，將kthread_create()和wake_up_process()包裝成kthread_run()，也就是調用了kthread_run()之後，該thread會立刻被執行。

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

MODULE_LICENSE("GPL");

static struct task_struct *brook_tsk;
static int data;
static int kbrook(void *arg);

static int kbrook(void *arg)
{
    unsigned int timeout;
    int *d = (int *) arg;

    for(;;) {
        if (kthread_should_stop()) break;
        printk("%s(): %d\n", __FUNCTION__, (*d)++);
        do {
            set_current_state(TASK_INTERRUPTIBLE);
            timeout = schedule_timeout(10 * HZ);
        } while(timeout);
    }
    printk("break\n");

    return 0;
}

static int __init init_modules(void)
{
    int ret;

    brook_tsk = kthread_create(kbrook, &data, "brook");
    if (IS_ERR(brook_tsk)) {
        ret = PTR_ERR(brook_tsk);
        brook_tsk = NULL;
        goto out;
    }
    wake_up_process(brook_tsk);

    return 0;

out:
    return ret;
}

static void __exit exit_modules(void)
{
    kthread_stop(brook_tsk);
}

module_init(init_modules);
module_exit(exit_modules);

linux/kthread.h

/**
 * kthread_run - create and wake a thread.
 * @threadfn: the function to run until signal_pending(current).
 * @data: data ptr for @threadfn.
 * @namefmt: printf-style name for the thread.
 *
 * Description: Convenient wrapper for kthread_create() followed by
 * wake_up_process().  Returns the kthread or ERR_PTR(-ENOMEM).
 */
#define kthread_run(threadfn, data, namefmt, ...)      \
({            \
 struct task_struct *__k         \
  = kthread_create(threadfn, data, namefmt, ## __VA_ARGS__); \
 if (!IS_ERR(__k))         \
  wake_up_process(__k);        \
 __k;           \
})