Linux kernel: kthread & wait_event_interruptible 사용법

Kernel thread에서event wait 사용 법

 

1. Dependencies

#include <linux/kthread.h> #include <linux/time.h> #include <linux/timer.h>

 

2. Declaring variables

static DECLARE_WAIT_QUEUE_HEAD(hub_wait_queue);   static struct {     unsigned int evt_thread_stt;     unsigned int evt_wait_cond;     struct task_struct *evt_kthread;       spinlock_t evt_thread_lock; } hub_wait_queue_ctx;

 

3. Condition check used by kthread

bool _hub_work_evt_check_cond() {     spin_lock(&hub_wait_queue_ctx.evt_thread_lock);     bool ret = hub_wait_queue_ctx.evt_wait_cond;     spin_unlock(&hub_wait_queue_ctx.evt_thread_lock);     return ret; }

 

4. kthread entry

int _hub_work_evt_thread_entry(void *param) { int ret; int timeout = 5000; unsigned long remain_timeout = 1; …   // 1. Without timeout ret = wait_event_interruptible(hub_wait_queue, _hub_work_evt_check_cond()); if (ret != 0) {     printk(KERN_WARNING "ERR: wait_event_interruptible\r\n"); }   // 2. With timeout remain_timeout = wait_event_interruptible_timeout(hub_wait_queue,    _hub_work_evt_check_cond(),    msecs_to_jiffies(timeout));   if (remain_timeout <= 0) {     printk(KERN_WARNING “ time out...\r\n");     continue; }   spin_lock(&hub_wait_queue_ctx.evt_thread_lock); hub_wait_queue_ctx.evt_wait_cond = false; spin_unlock(&hub_wait_queue_ctx.evt_thread_lock); … }

 

5. ISR

unsigned long irqflags;     spin_lock_irqsave(&hub_wait_queue_ctx.evt_thread_lock, irqflags);     hub_wait_queue_ctx.evt_wait_cond = true;     spin_unlock_irqrestore(&hub_wait_queue_ctx.evt_thread_lock, irqflags);         wake_up_interruptible(&hub_wait_queue);

 

6. init

spin_lock_init(&hub_wait_queue_ctx.evt_thread_lock);     hub_wait_queue_ctx.evt_wait_cond = false;         hub_wait_queue_ctx.evt_thread_stt = 1;     hub_wait_queue_ctx.evt_kthread = kthread_run(_hub_work_evt_thread_entry, NULL, "Evt_kthread");     if (IS_ERR(hub_wait_queue_ctx.evt_kthread)) {         pr_err("ERR: errno:%p\n", hub_wait_queue_ctx.evt_kthread);         return NULL;     }

 

7. deinit

hub_wait_queue_ctx.evt_thread_stt = 0;     kthread_stop(hub_wait_queue_ctx.evt_kthread);