共享隊列
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/*
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* jiq.c -- the just-in-queue module
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*
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* Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
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* Copyright (C) 2001 O'Reilly & Associates
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*
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* The source code in this file can be freely used, adapted,
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* and redistributed in source or binary form, so long as an
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* acknowledgment appears in derived source files. The citation
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* should list that the code comes from the book "Linux Device
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* Drivers" by Alessandro Rubini and Jonathan Corbet, published
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* by O'Reilly & Associates. No warranty is attached;
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* we cannot take responsibility for errors or fitness for use.
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*
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* $Id: jiq.c,v 1.7 2004/09/26 07:02:43 gregkh Exp $
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*/
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/fs.h> /* everything... */
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#include <linux/proc_fs.h>
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#include <linux/errno.h> /* error codes */
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#include <linux/workqueue.h>
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#include <linux/preempt.h>
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#include <linux/interrupt.h> /* tasklets */
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/*
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* The delay for the delayed workqueue timer file.
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*/
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static long delay = 1;
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module_param(delay, long, 0);
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/*
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* This module is a silly one: it only embeds short code fragments
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* that show how enqueued tasks `feel' the environment
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*/
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#define LIMIT (512) /* don't print any more after this size */
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/*
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* Print information about the current environment. This is called from
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* within the task queues. If the limit is reched, awake the reading
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* process.
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*/
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static DECLARE_WAIT_QUEUE_HEAD (jiq_wait);
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static struct work_struct jiq_work;
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static struct delayed_work jiq_work_delay;
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/*
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* Keep track of info we need between task queue runs.
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*/
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static struct clientdata {
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int len;
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char *buf;
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unsigned long jiffies;
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unsigned long delay;
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} jiq_data;
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#define SCHEDULER_QUEUE ((task_queue *) 1)
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static void jiq_print_tasklet(unsigned long);
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static DECLARE_TASKLET(jiq_tasklet, jiq_print_tasklet, (unsigned long)&jiq_data);
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/*
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* Do the printing; return non-zero if the task should be rescheduled.
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*/
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static int jiq_print(void *ptr)
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{
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struct clientdata *data = ptr;
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int len = data->len;
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char *buf = data->buf;
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unsigned long j = jiffies;
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//error , full
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if (len > LIMIT)
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{
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wake_up_interruptible(&jiq_wait);
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return 0;
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}
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//the first time to show the message
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if (len == 0)
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len = sprintf(buf," time delta preempt pid cpu commandn");
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else
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len =0; //init again
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/* intr_count is only exported since 1.3.5, but 1.99.4 is needed anyways */
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len += sprintf(buf, "%9li %4li %3i %5i %3i %sn",
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j, j - data->jiffies,
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preempt_count(), current->pid, smp_processor_id(),
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current->comm);
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data->len += len;
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data->buf += len;
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data->jiffies = j;
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return 1;
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}
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/*
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* Call jiq_print from a work queue
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*/
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static void jiq_print_wq(struct work_struct *ptr) /* warning: assignment from incompatible pointer type*/
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{
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struct clientdata *data = &jiq_data;
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if (! jiq_print (data))
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return;
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//to schedule again, so jiq_work <===> jiq_print_wq() will be call again
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if (data->delay)
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schedule_delayed_work( &jiq_work_delay, data->delay);
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else
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schedule_work(&jiq_work);
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}
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static int jiq_read_wq(char *buf, char **start, off_t offset,
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int len, int *eof, void *data)
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{
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DEFINE_WAIT(wait);
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jiq_data.len = 0; /* nothing printed, yet */
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jiq_data.buf = buf; /* print in this place */
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jiq_data.jiffies = jiffies; /* initial time */
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jiq_data.delay = 0;
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//add jiq_wait into the waitquene
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prepare_to_wait(&jiq_wait, &wait, TASK_INTERRUPTIBLE);
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//use this method, jiq_work <===> jiq_print_wq() will be call(here is very important)
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schedule_work(&jiq_work);
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//here sleep and wait
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schedule();
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//cleanup the waitquene
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finish_wait(&jiq_wait, &wait);
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*eof = 1;
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return jiq_data.len;
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}
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static int jiq_read_wq_delayed(char *buf, char **start, off_t offset,
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int len, int *eof, void *data)
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{
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DEFINE_WAIT(wait);
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jiq_data.len = 0; /* nothing printed, yet */
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jiq_data.buf = buf; /* print in this place */
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jiq_data.jiffies = jiffies; /* initial time */
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jiq_data.delay = delay;
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prepare_to_wait(&jiq_wait, &wait, TASK_INTERRUPTIBLE);
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schedule_delayed_work(&jiq_work_delay, delay);
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schedule();
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finish_wait(&jiq_wait, &wait);
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*eof = 1;
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return jiq_data.len;
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}
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/*
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* Call jiq_print from a tasklet
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*/
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static void jiq_print_tasklet(unsigned long ptr)
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{
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if (!jiq_print ((void *) ptr))
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return;
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//to schedule it again
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tasklet_schedule (&jiq_tasklet);
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}
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static int jiq_read_tasklet(char *buf, char **start, off_t offset, int len,
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int *eof, void *data)
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{
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jiq_data.len = 0; /* nothing printed, yet */
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jiq_data.buf = buf; /* print in this place */
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jiq_data.jiffies = jiffies; /* initial time */
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tasklet_schedule(&jiq_tasklet);
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//here interruptible_sleep_on is not a good method
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//try to use 手動休眠
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interruptible_sleep_on(&jiq_wait); /* sleep utill completion */
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*eof = 1;
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return jiq_data.len;
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}
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/*
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* This one, instead, tests out the timers.
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*/
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static struct timer_list jiq_timer;
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static void jiq_timedout(unsigned long ptr)
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{
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struct clientdata *data = ptr;
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//jiq_print((void *)ptr); /* print a line */
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//wake_up_interruptible(&jiq_wait); /* awake the process */
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if (! jiq_print (data))
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{
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wake_up_interruptible(&jiq_wait); /* awake the process */
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return;
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}
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//update the timer
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mod_timer(&jiq_timer, jiq_timer.expires+HZ);
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}
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static int jiq_read_run_timer(char *buf, char **start, off_t offset,
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int len, int *eof, void *data)
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{
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jiq_data.len = 0; /* prepare the argument for jiq_print() */
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jiq_data.buf = buf;
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jiq_data.jiffies = jiffies;
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init_timer(&jiq_timer); /* init the timer structure */
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jiq_timer.function = jiq_timedout;
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jiq_timer.data = (unsigned long)&jiq_data;
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jiq_timer.expires = jiffies + HZ; /* one second */
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jiq_print(&jiq_data); /* print and go to sleep */
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add_timer(&jiq_timer);
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interruptible_sleep_on(&jiq_wait); /* RACE */
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del_timer_sync(&jiq_timer); /* in case a signal woke us up */
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*eof = 1;
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return jiq_data.len;
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}
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/*
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* the init/clean material
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*/
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static int jiq_init(void)
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{
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/* this line is in jiq_init() */
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INIT_WORK(&jiq_work, jiq_print_wq);
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INIT_DELAYED_WORK(&jiq_work_delay, jiq_print_wq);
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create_proc_read_entry("jiqwq", 0, NULL, jiq_read_wq, NULL);
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create_proc_read_entry("jiqwqdelay", 0, NULL, jiq_read_wq_delayed, NULL);
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create_proc_read_entry("jiqtimer", 0, NULL, jiq_read_run_timer, NULL);
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create_proc_read_entry("jiqtasklet", 0, NULL, jiq_read_tasklet, NULL);
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return 0; /* succeed */
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}
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static void jiq_cleanup(void)
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{
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remove_proc_entry("jiqwq", NULL);
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remove_proc_entry("jiqwqdelay", NULL);
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remove_proc_entry("jiqtimer", NULL);
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remove_proc_entry("jiqtasklet", NULL);
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}
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module_init(jiq_init);
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module_exit(jiq_cleanup);
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MODULE_LICENSE("Dual BSD/GPL");
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