linux 0.12: 我对add_timer的修改

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今天看到add_timer函数，注释中说这个有点问题。我仔细看了一下，果然有点问题。

自己修正了一下，还请大家看看。红色部分是我改的。不过貌似free_timer这个东西还是有点问题。

源代码如下：
/*
*  linux/kernel/sched.c
*
*  This piece of code is copied from Linux Kernel 0.12.
*  Since the timer for kernel has a minor bug, I want to fix it.
*  (C) 1991  Linus Torvalds
*/

#include <stdio.h>
#define TIME_REQUESTS 64
static struct timer_list {
long jiffies;
void (*fn)();
struct timer_list * next;
} timer_list[TIME_REQUESTS], * next_timer = NULL;
static struct timer_list timer_list_test[TIME_REQUESTS], * next_timer_test = NULL;
/* kernel function with out change */
void add_timer(long jiffies, void (*fn)(void))
{
struct timer_list * p;
if (!fn)
  return;
//cli();
if (jiffies <= 0)
  (fn)();
else {
  for (p = timer_list ; p < timer_list + TIME_REQUESTS ; p++)
if (!p->fn)
break;
  if (p >= timer_list + TIME_REQUESTS)
return;
//panic("No more time requests free");
  p->fn = fn;
  p->jiffies = jiffies;
  p->next = next_timer;
  next_timer = p;
  while (p->next && p->next->jiffies < p->jiffies) {
p->jiffies -= p->next->jiffies;
fn = p->fn;
p->fn = p->next->fn;
p->next->fn = fn;
jiffies = p->jiffies;
p->jiffies = p->next->jiffies;
p->next->jiffies = jiffies;
p = p->next;
  }
}
//sti();
}
/* my version */
void add_timer_test(long jiffies, void (*fn)(void))
{
struct timer_list * p;
if (!fn)
  return;
//cli();
if (jiffies <= 0)
  (fn)();
else {
  for (p = timer_list_test ; p < timer_list_test + TIME_REQUESTS ; p++)
if (!p->fn)
break;
  if (p >= timer_list_test + TIME_REQUESTS)
return;
//panic("No more time requests free");
  p->fn = fn;
  p->jiffies = jiffies;
  p->next = next_timer_test;
  next_timer_test = p;
  while (p->next) {
if ( p->jiffies <= p->next->jiffies)
{
p->next->jiffies -= p->jiffies;
break;
}
p->jiffies -= p->next->jiffies;
fn = p->fn;
p->fn = p->next->fn;
p->next->fn = fn;
jiffies = p->jiffies;
p->jiffies = p->next->jiffies;
p->next->jiffies = jiffies;
p = p->next;
  }
}
//sti();
}
void dump_timer(struct timer_list * p)
{

int sum = 0, i = 1;

printf("/tTimer node/trelative time/tabsolute time/n");
while (p)
{
  sum += p->jiffies;
  printf("/t%6d  /t%8d /t%8d/n", i, p->jiffies, sum);
  p = p->next;
  i++;
}
return;
}
void free_timer(struct timer_list * * p)
{
struct timer_list **start = p;
struct timer_list *liter = *p, *m;
for (m ; m < liter + TIME_REQUESTS; m++)
{
  m->fn = NULL;
  m->jiffies = 0;
  m->next = NULL;
}
*start = NULL;
return;
}
void handler()
{
printf("handler here/n");
return;
}
void main()
{
printf("This is a bug fixing for linux kernel. /n");
/*linux kernel test*/
add_timer(5, handler);
add_timer(10, handler);
add_timer(20, handler);
dump_timer(next_timer);
free_timer(&next_timer);
dump_timer(next_timer);
printf("-----------------------------/n");
add_timer(20, handler);
add_timer(10, handler);
add_timer(30, handler);
dump_timer(next_timer);
free_timer(&next_timer);
dump_timer(next_timer);
printf("-----------------------------/n");

/*my function test*/
add_timer_test(5, handler);
add_timer_test(10, handler);
add_timer_test(20, handler);
dump_timer(next_timer_test);
free_timer(&next_timer_test);
dump_timer(next_timer_test);
printf("-----------------------------/n");
add_timer_test(20, handler);
add_timer_test(10, handler);
add_timer_test(30, handler);
dump_timer(next_timer_test);
free_timer(&next_timer_test);
dump_timer(next_timer_test);
printf("-----------------------------/n");
return;
}

下面是运行的结果。

This is a bug fixing for linux kernel.
      Timer node    relative time absolute time
         1                5             5
         2                5             10
         3             10             20
      Timer node    relative time absolute time
-----------------------------
      Timer node    relative time absolute time
         1             10             10
         2             20             30
         3             20             50
      Timer node    relative time absolute time
-----------------------------
      Timer node    relative time absolute time
         1                5             5
         2                5             10
         3             10             20
      Timer node    relative time absolute time
-----------------------------
      Timer node    relative time absolute time
         1             10             10
         2             10             20
         3             10             30
      Timer node    relative time absolute time
-----------------------------
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