Linux设备驱动程序学习（10）-时间、延迟及延缓操作（Jiq.c）

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/*
 * jiq.c -- the just-in-queue module
 *
 * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
 * Copyright (C) 2001 O'Reilly & Associates
 *
 * The source code in this file can be freely used, adapted,
 * and redistributed in source or binary form, so long as an
 * acknowledgment appears in derived source files. The citation
 * should list that the code comes from the book "Linux Device
 * Drivers" by Alessandro Rubini and Jonathan Corbet, published
 * by O'Reilly & Associates. No warranty is attached;
 * we cannot take responsibility for errors or fitness for use.
 *
 * $Id: jiq.c,v 1.7 2004/09/26 07:02:43 gregkh Exp $
 */
 
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/fs.h> /* everything... */
#include <linux/proc_fs.h>
#include <linux/errno.h> /* error codes */
#include <linux/workqueue.h>
#include <linux/preempt.h>
#include <linux/interrupt.h> /* tasklets */



/*
 * The delay for the delayed workqueue timer file.
 */
static long delay = 1;
module_param(delay, long, 0);


/*
 * This module is a silly one: it only embeds short code fragments
 * that show how enqueued tasks `feel' the environment
 */

#define LIMIT    (512)    /* don't print any more after this size */

/*
 * Print information about the current environment. This is called from
 * within the task queues. If the limit is reched, awake the reading
 * process.
 */
static DECLARE_WAIT_QUEUE_HEAD (jiq_wait);


static struct work_struct jiq_work;
static struct delayed_work jiq_work_delay;


/*
 * Keep track of info we need between task queue runs.
 */
static struct clientdata {
    int len;
    char *buf;
    unsigned long jiffies;
    unsigned long delay;
} jiq_data;

#define SCHEDULER_QUEUE ((task_queue *) 1)



static void jiq_print_tasklet(unsigned long);
static DECLARE_TASKLET(jiq_tasklet, jiq_print_tasklet, (unsigned long)&jiq_data);


/*
 * Do the printing; return non-zero if the task should be rescheduled.
 */
static int jiq_print(void *ptr)
{
    struct clientdata *data = ptr;
    int len = data->len;
    char *buf = data->buf;
    unsigned long j = jiffies;

    //error , full
    if (len > LIMIT) 
    { 
        wake_up_interruptible(&jiq_wait);
        return 0;
    }

    //the first time to show the message
    if (len == 0)
        len = sprintf(buf," time delta preempt pid cpu commandn");
    else
        len =0;    //init again

      /* intr_count is only exported since 1.3.5, but 1.99.4 is needed anyways */
    len += sprintf(buf, "%9li %4li %3i %5i %3i %sn",
            j, j - data->jiffies,
            preempt_count(), current->pid, smp_processor_id(),
            current->comm);

    data->len += len;
    data->buf += len;
    data->jiffies = j;
    return 1;
}


/*
 * Call jiq_print from a work queue
 */
static void jiq_print_wq(struct work_struct *ptr) /* warning: assignment from incompatible pointer type*/
{
    struct clientdata *data = &jiq_data;

    if (! jiq_print (data))
        return;

    //to schedule again, so jiq_work <===> jiq_print_wq() will be call again
    if (data->delay)
        schedule_delayed_work( &jiq_work_delay, data->delay);
    else
        schedule_work(&jiq_work);
}



static int jiq_read_wq(char *buf, char **start, off_t offset,
                   int len, int *eof, void *data)
{
    DEFINE_WAIT(wait);
    
    jiq_data.len = 0; /* nothing printed, yet */
    jiq_data.buf = buf; /* print in this place */
    jiq_data.jiffies = jiffies; /* initial time */
    jiq_data.delay = 0;

    //add jiq_wait into the waitquene
    prepare_to_wait(&jiq_wait, &wait, TASK_INTERRUPTIBLE);
    //use this method, jiq_work <===> jiq_print_wq() will be call(here is very important)
    schedule_work(&jiq_work);
    //here sleep and wait
    schedule();
    //cleanup the waitquene
    finish_wait(&jiq_wait, &wait);

    *eof = 1;
    return jiq_data.len;
}


static int jiq_read_wq_delayed(char *buf, char **start, off_t offset,
                   int len, int *eof, void *data)
{
    DEFINE_WAIT(wait);
    
    jiq_data.len = 0; /* nothing printed, yet */
    jiq_data.buf = buf; /* print in this place */
    jiq_data.jiffies = jiffies; /* initial time */
    jiq_data.delay = delay;
    
    prepare_to_wait(&jiq_wait, &wait, TASK_INTERRUPTIBLE);
    schedule_delayed_work(&jiq_work_delay, delay);
    schedule();
    finish_wait(&jiq_wait, &wait);

    *eof = 1;
    return jiq_data.len;
}




/*
 * Call jiq_print from a tasklet
 */
static void jiq_print_tasklet(unsigned long ptr)
{
    if (!jiq_print ((void *) ptr))
        return;

    //to schedule it again
    tasklet_schedule (&jiq_tasklet);
}



static int jiq_read_tasklet(char *buf, char **start, off_t offset, int len,
                int *eof, void *data)
{
    jiq_data.len = 0; /* nothing printed, yet */
    jiq_data.buf = buf; /* print in this place */
    jiq_data.jiffies = jiffies; /* initial time */

    tasklet_schedule(&jiq_tasklet);
    //here interruptible_sleep_on is not a good method
    //try to use 手動休眠
    interruptible_sleep_on(&jiq_wait); /* sleep utill completion */

    *eof = 1;
    return jiq_data.len;
}




/*
 * This one, instead, tests out the timers.
 */

static struct timer_list jiq_timer;

static void jiq_timedout(unsigned long ptr)
{
    struct clientdata *data = ptr;
    //jiq_print((void *)ptr); /* print a line */
    //wake_up_interruptible(&jiq_wait); /* awake the process */

    if (! jiq_print (data))
    {
        wake_up_interruptible(&jiq_wait); /* awake the process */
        return;
    }
    //update the timer
    mod_timer(&jiq_timer, jiq_timer.expires+HZ);
}


static int jiq_read_run_timer(char *buf, char **start, off_t offset,
                   int len, int *eof, void *data)
{

    jiq_data.len = 0; /* prepare the argument for jiq_print() */
    jiq_data.buf = buf;
    jiq_data.jiffies = jiffies;

    init_timer(&jiq_timer); /* init the timer structure */
    jiq_timer.function = jiq_timedout;
    jiq_timer.data = (unsigned long)&jiq_data;
    jiq_timer.expires = jiffies + HZ; /* one second */

    jiq_print(&jiq_data); /* print and go to sleep */
    add_timer(&jiq_timer);
    interruptible_sleep_on(&jiq_wait); /* RACE */
    del_timer_sync(&jiq_timer); /* in case a signal woke us up */
    
    *eof = 1;
    return jiq_data.len;
}



/*
 * the init/clean material
 */

static int jiq_init(void)
{

    /* this line is in jiq_init() */
    INIT_WORK(&jiq_work, jiq_print_wq);
    INIT_DELAYED_WORK(&jiq_work_delay, jiq_print_wq);
    create_proc_read_entry("jiqwq", 0, NULL, jiq_read_wq, NULL);
    create_proc_read_entry("jiqwqdelay", 0, NULL, jiq_read_wq_delayed, NULL);
    create_proc_read_entry("jiqtimer", 0, NULL, jiq_read_run_timer, NULL);
    create_proc_read_entry("jiqtasklet", 0, NULL, jiq_read_tasklet, NULL);

    return 0; /* succeed */
}

static void jiq_cleanup(void)
{
    remove_proc_entry("jiqwq", NULL);
    remove_proc_entry("jiqwqdelay", NULL);
    remove_proc_entry("jiqtimer", NULL);
    remove_proc_entry("jiqtasklet", NULL);
}


module_init(jiq_init);
module_exit(jiq_cleanup);

MODULE_LICENSE("Dual BSD/GPL");
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