linux内核原代码sched.c的注释

　　/*
　　* 'sched.c' is the main kernel file. It contains scheduling primitives
　　* (sleep_on, wakeup, schedule etc) as well as a number of simple system
　　* call functions (type getpid(), which just extracts a field from
　　* current-task
　　*/
　　#include
　　#include
　　#include
　　#include
　　#include
　　#include
　　#include

#define LATCH (1193180/HZ)

extern void mem_use(void);

extern int timer_interrupt(void);
　　extern int system_call(void);

union task_union {
　　struct task_struct task;
　　char stack[PAGE_SIZE];
　　};

static union task_union init_task = {INIT_TASK,};

long volatile jiffies=0;
　　long startup_time=0;
　　struct task_struct *current = &(init_task.task), *last_task_used_math =
　　NULL;

struct task_struct * task[NR_TASKS] = {&(init_task.task), };

long user_stack [ PAGE_SIZE>>2 ] ;

struct {
　　long * a;
　　short b;
　　} stack_start = { & user_stack [PAGE_SIZE>>2] , 0x10 };
　　/*
　　* 'math_state_restore()' saves the current math information in the
　　* old math state array, and gets the new ones from the current task
　　*/
　　void math_state_restore() @@协处理器状态保存
　　{
　　if (last_task_used_math)
　　 __asm__("fnsave %0"::"m" (last_task_used_math->tss.i387));
　　if (current->used_math)
　　 __asm__("frstor %0"::"m" (current->tss.i387));
　　else {
　　 __asm__("fninit"::);
　　 current->used_math=1;
　　}
　　last_task_used_math=current;
　　}

/*
　　* 'schedule()' is the scheduler function. This is GOOD CODE! There
　　* probably won't be any reason to change this, as it should work well
　　* in all circumstances (ie gives IO-bound processes good response etc).

* The one thing you might take a look at is the signal-handler code
　　here.
　　*
　　* NOTE!! Task 0 is the 'idle' task, which gets called when no other
　　* tasks can run. It can not be killed, and it cannot sleep. The 'state'

* information in task[0] is never used.
　　*/
　　void schedule(void)
　　{
　　int i,next,c;
　　struct task_struct ** p;

/* check alarm, wake up any interruptible tasks that have got a signal
　　*/

for(p = &LAST_TASK ; p >&FIRST_TASK ; --p)
　　 if (*p) {
　　 if ((*p)->alarm && (*p)->alarm signal |= (1alarm = 0;
　　 }
　　 if ((*p)->signal && (*p)->state==TASK_INTERRUPTIBLE)