http://code.google.com/p/ldd3/source/browse/trunk/misc-modules/jiq.c?r=2
/*
* 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/config.h>
#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 */
MODULE_LICENSE("Dual BSD/GPL");
/*
* 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 (PAGE_SIZE-128) /* 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;
/*
* Keep track of info we need between task queue runs.
*/
static struct clientdata {
int len;
char *buf;
unsigned long jiffies;
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;
if (len > LIMIT) {
wake_up_interruptible(&jiq_wait);
return 0;
}
if (len == 0)
len = sprintf(buf," time delta preempt pid cpu command\n");
else
len =0;
/* intr_count is only exported since 1.3.5, but 1.99.4 is needed anyways */
len += sprintf(buf+len, "%9li %4li %3i %5i %3i %s\n",
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(void *ptr)
{
struct clientdata *data = (struct clientdata *) ptr;
if (! jiq_print (ptr))
return;
if (data->delay)
schedule_delayed_work(&jiq_work, 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;
prepare_to_wait(&jiq_wait, &wait, TASK_INTERRUPTIBLE);
schedule_work(&jiq_work);
schedule();
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);
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))
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);
interruptible_sleep_on(&jiq_wait); /* sleep till 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)
{
jiq_print((void *)ptr); /* print a line */
wake_up_interruptible(&jiq_wait); /* awake the process */
}
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, &jiq_data);
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("jitimer", 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("jitimer", NULL);
remove_proc_entry("jiqtasklet", NULL);
}
module_init(jiq_init);
module_exit(jiq_cleanup);