一、基于事件的任务调度器

1.事件任务调度器数据结构

typedef unsigned char      bit_t;typedef unsigned char      u1_t;typedef   signed char      s1_t;typedef unsigned short     u2_t;typedef          short     s2_t;typedef unsigned int       u4_t;typedef          int       s4_t;typedef unsigned long long u8_t;typedef          long long s8_t;typedef unsigned int       uint;typedef const char* str_t;typedef s4_t  ostime_t;struct  osjob_t;  typedef void (*osjobcb_t) (struct osjob_t*);struct osjob_t {    struct osjob_t* next;//链表    ostime_t deadline;//任务执行事件    osjobcb_t  func; //任务函数};TYPEDEF_xref2osjob_t;// RUNTIME STATE 用于记录当前即时任务及计划任务；即时任务添加进即时任务链表后即时运行；计划任务则为计时时间到则运行。static struct {    osjob_t* scheduledjobs; /* 计划任务 */    osjob_t* runnablejobs; /* 即时任务 */} OS;

任务的添加和删除工作，都以回调的形式完成。

2.OS初始化及时基

/*   系统初始化，如定时器、中断等 */void os_init () {/* hal_init();  */} /*   获取系统时间，需要消耗MCU一个定时器来实现OS系统时基 */ostime_t os_getTime () {    return hal_ticks();}

3.任务及任务链表

任务链表分两个，一个为即时任务链表，一个为定时任务链表；删除时需要从两个表中寻找并删除。

从任务链表中删除指定任务

static u1_t unlinkjob (osjob_t** pnext, osjob_t* job) {    for( ; *pnext; pnext = &((*pnext)->next)) {        if(*pnext == job) { // unlink            *pnext = job->next;            return 1;        }    }    return 0;}// clear scheduled jobvoid os_clearCallback (osjob_t* job) {    hal_disableIRQs();    unlinkjob(&OS.scheduledjobs, job) || unlinkjob(&OS.runnablejobs, job);    hal_enableIRQs();}

添加任务至即时任务链表

// schedule immediately runnable jobvoid os_setCallback (osjob_t* job, osjobcb_t cb) {    osjob_t** pnext;    hal_disableIRQs();    // remove if job was already queued    os_clearCallback(job);    // fill-in job    job->func = cb;    job->next = NULL;    // add to end of run queue    for(pnext=&OS.runnablejobs; *pnext; pnext=&((*pnext)->next));    *pnext = job;    hal_enableIRQs();}

添加任务至计划任务链表

// schedule timed jobvoid os_setTimedCallback (osjob_t* job, ostime_t time, osjobcb_t cb) {    osjob_t** pnext;    hal_disableIRQs();    // remove if job was already queued    os_clearCallback(job);    // fill-in job    job->deadline = time;    job->func = cb;    job->next = NULL;    // insert into schedule    for(pnext=&OS.scheduledjobs; *pnext; pnext=&((*pnext)->next)) {        if((*pnext)->deadline - time > 0) { // (cmp diff, not abs!)            // enqueue before next element and stop            job->next = *pnext;            break;        }    }    *pnext = job;    hal_enableIRQs();}

4.任务后台

优先从即时任务中提取任务运行，即时任务运行完成后，才会再运行计划任务。所以，计划任务一般给对实时性无要求的任务，有时候为了保证即时任务，需要将一些任务设定为计划任务，如：点灯任务。

// execute jobs from timer and from run queuevoid os_runloop () {    while(1) {        osjob_t* j = NULL;        hal_disableIRQs();        // check for runnable jobs        if(OS.runnablejobs) {            j = OS.runnablejobs;            OS.runnablejobs = j->next;        } else if(OS.scheduledjobs                      && hal_checkTimer(OS.scheduledjobs->deadline)) {                    // check for expired timed jobs            j = OS.scheduledjobs;            OS.scheduledjobs = j->next;        } else { // nothing pending            hal_sleep(); // wake by irq (timer already restarted)        }        hal_enableIRQs();        if(j) { // run job callback            j->func(j);        }    }}

5.任务调度实例

static void immediatelyfunc (osjob_t* j) {/*TODO*/}static void scheduledfunc (osjob_t* j) {/*TODO*/}// application entry pointint main () {    osjob_t immediatelyjob;    osjob_t scheduledjob;    // initialize runtime env    os_init();    // setup initial job 添加即时任务    os_setCallback(&immediatelyjob, immediatelyfunc);    // execute scheduled jobs and events    os_setTimedCallback (&scheduledjob, 1000, scheduledfunc)    os_runloop();// (not reached)    return 0;}