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ϵͳµ÷ÓÃtime£¨£©ÓÃÓÚ»ñÈ¡ÒÔÃëÊý±íʾµÄϵͳµ±Ç°Ê±¼ä£¨¼´ÄÚºËÈ«¾Öʱ¼ä±äÁ¿xtimeÖеÄtv_sec³ÉÔ±µÄÖµ£©¡£ËüÖ»ÓÐÒ»¸ö²ÎÊý----ÕûÐÍÖ¸Õëtloc£¬Ö¸ÏòÓû§¿Õ¼äÖеÄÒ»¸öÕûÊý£¬ÓÃÀ´½ÓÊÕ·µ»ØµÄµ±Ç°Ê±¼äÖµ¡£º¯Êýsys_time£¨£©µÄÔ´ÂëÈçÏ£¨kernel/time.c£©£º
asmlinkage long sys_time(int * tloc)
{
int i;
/* SMP: This is fairly trivial. We grab CURRENT_TIME and
stuff it to user space. No side effects */
i = CURRENT_TIME;
if (tloc) {
if (put_user(i,tloc))
i = -EFAULT;
}
return i;
}
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£¨1£©Ê×ÏÈ£¬º¯Êýµ÷ÓÃCURRENT_TIMEºêÀ´µÃµ½ÒÔÃëÊý±íʾµÄÄں˵±Ç°Ê±¼äÖµ£¬²¢½«¸ÃÖµ±£´æÔÚ¾Ö²¿±äÁ¿iÖС£ºêCURRENT_TIME¶¨ÒåÔÚinclude/linux/sched.hÍ·ÎļþÖУ¬Ëüʵ¼ÊÉϾÍÊÇÄÚºËÈ«¾Öʱ¼ä±äÁ¿xtimeÖеÄtv_sec³ÉÔ±¡£ÈçÏÂËùʾ£º
#define CURRENT_TIME (xtime.tv_sec)
£¨2£©È»ºó£¬ÔÚ²ÎÊýÖ¸Õëtloc·Ç¿ÕµÄÇé¿öϽ«iµÄֵͨ¹ýput_user()ºê´«µÝµ½ÓÐtlocËùÖ¸ÏòµÄÓû§¿Õ¼äÖÐÈ¥£¬ÒÔ×÷Ϊº¯ÊýµÄÊä³ö½á¹û¡£
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ϵͳµ÷ÓÃstime()Óëϵͳµ÷ÓÃtime()¸ÕºÃÏà·´£¬Ëü¿ÉÒÔÈÃÓû§ÉèÖÃϵͳµÄµ±Ç°Ê±¼ä£¨ÒÔÃëÊýΪµ¥Î»£©¡£ËüͬÑùÒ²Ö»ÓÐÒ»¸ö²ÎÊý----ÕûÐÍÖ¸Õëtptr£¬Ö¸ÏòÓû§¿Õ¼äÖдýÉèÖõÄʱ¼äÃëÊýÖµ¡£º¯Êýsys_stime()µÄÔ´ÂëÈçÏ£¨kernel/time.c£©£º
asmlinkage long sys_stime(int * tptr)
{
int value;
if (!capable(CAP_SYS_TIME))
return -EPERM;
if (get_user(value, tptr))
return -EFAULT;
write_lock_irq(&xtime_lock);
xtime.tv_sec = value;
hfh08 ÓÚ 2006-08-21 00:26:37·¢±í:
7£®7 ½ø³Ì¼ä¸ô¶¨Ê±Æ÷itimer
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¼ä¸ô¶¨Ê±Æ÷Ö÷Òª±»Ó¦ÓÃÔÚÓû§½ø³ÌÉÏ¡£Ã¿¸öLinux½ø³Ì¶¼ÓÐÈý¸öÏ໥¹ØÁªµÄ¼ä¸ô¶¨Ê±Æ÷¡£Æä¸÷×Եļä¸ô¼ÆÊýÆ÷¶¼¶¨ÒåÔÚ½ø³ÌµÄtask_struct½á¹¹ÖУ¬ÈçÏÂËùʾ£¨include/linux/sched.h£©£º
struct task_struct£û
¡¡
unsigned long it_real_value, it_prof_value, it_virt_value;
unsigned long it_real_incr, it_prof_incr, it_virt_incr;
struct timer_list real_timer;
¡¡
}
£¨1£©Õæʵ¼ä¸ô¶¨Ê±Æ÷£¨ITIMER_REAL£©£ºÕâÖÖ¼ä¸ô¶¨Ê±Æ÷ÔÚÆô¶¯ºó£¬²»¹Ü½ø³ÌÊÇ·ñÔËÐУ¬Ã¿¸öʱÖӵδ𶼽«Æä¼ä¸ô¼ÆÊýÆ÷¼õ1¡£µ±¼õµ½0ֵʱ£¬ÄÚºËÏò½ø³Ì·¢ËÍSIGALRMÐźš£½á¹¹ÀàÐÍtask_structÖеijÉÔ±it_real_incrÔò±íʾÕæʵ¼ä¸ô¶¨Ê±Æ÷µÄ¼ä¸ô¼ÆÊýÆ÷µÄ³õʼֵ£¬¶ø³ÉÔ±it_real_valueÔò±íʾÕæʵ¼ä¸ô¶¨Ê±Æ÷µÄ¼ä¸ô¼ÆÊýÆ÷µÄµ±Ç°Öµ¡£ÓÉÓÚÕâÖÖ¼ä¸ô¶¨Ê±Æ÷±¾ÖÊÉÏÓëÉÏÒ»½ÚµÄÄں˶¨Ê±Æ÷ʱһÑùµÄ£¬Òò´ËLinuxʵ¼ÊÉÏÊÇͨ¹ýreal_timerÕâ¸öÄÚǶÔÚtask_struct½á¹¹ÖеÄÄں˶¯Ì¬¶¨Ê±Æ÷À´ÊµÏÖÕæʵ¼ä¸ô¶¨Ê±Æ÷ITIMER_REALµÄ¡£
£¨2£©ÐéÄâ¼ä¸ô¶¨Ê±Æ÷ITIMER_VIRT£ºÒ²³ÆΪ½ø³ÌµÄÓû§Ì¬¼ä¸ô¶¨Ê±Æ÷¡£½á¹¹ÀàÐÍtask_structÖгÉÔ±it_virt_incrºÍit_virt_value·Ö±ð±íʾÐéÄâ¼ä¸ô¶¨Ê±Æ÷µÄ¼ä¸ô¼ÆÊýÆ÷µÄ³õʼֵºÍµ±Ç°Öµ£¬¶þÕß¾ùÒÔʱÖӵδð´ÎÊýλ¼ÆÊýµ¥Î»¡£µ±ÐéÄâ¼ä¸ô¶¨Ê±Æ÷Æô¶¯ºó£¬Ö»Óе±½ø³ÌÔÚÓû§Ì¬ÏÂÔËÐÐʱ£¬Ò»´ÎʱÖӵδð²ÅÄÜʹ¼ä¸ô¼ÆÊýÆ÷µ±Ç°Öµit_virt_value¼õ1¡£µ±¼õµ½0ֵʱ£¬ÄÚºËÏò½ø³Ì·¢ËÍSIGVTALRMÐźţ¨ÐéÄâÄÖÖÓÐźţ©£¬²¢½«it_virt_valueÖØÖÃΪ³õÖµit_virt_incr¡£¾ßÌåÇë¼û7.4.3½ÚÖеÄdo_it_virt()º¯ÊýµÄʵÏÖ¡£
£¨3£©PROF¼ä¸ô¶¨Ê±Æ÷ITIMER_PROF£º½ø³ÌµÄtask_struct½á¹¹ÖеÄit_prof_valueºÍit_prof_incr³ÉÔ±·Ö±ð±íʾPROF¼ä¸ô¶¨Ê±Æ÷µÄ¼ä¸ô¼ÆÊýÆ÷µÄµ±Ç°ÖµºÍ³õʼֵ£¨¾ùÒÔʱÖӵδðΪµ¥Î»£©¡£µ±Ò»¸ö½ø³ÌµÄPROF¼ä¸ô¶¨Ê±Æ÷Æô¶¯ºó£¬ÔòÖ»Òª¸Ã½ø³Ì´¦ÓÚÔËÐÐÖУ¬¶ø²»¹ÜÊÇÔÚÓû§Ì¬»òºËÐÄ̬ÏÂÖ´ÐУ¬Ã¿¸öʱÖӵδð¶¼Ê¹¼ä¸ô¼ÆÊýÆ÷it_prof_valueÖµ¼õ1¡£µ±¼õµ½0ֵʱ£¬ÄÚºËÏò½ø³Ì·¢ËÍSIGPROFÐźţ¬²¢½«it_prof_valueÖØÖÃΪ³õÖµit_prof_incr¡£¾ßÌåÇë¼û7.4.3½ÚµÄdo_it_prof()º¯Êý¡£
LinuxÔÚinclude/linux/time.hÍ·ÎļþÖÐΪÉÏÊöÈýÖÖ½ø³Ì¼ä¸ô¶¨Ê±Æ÷¶¨ÒåÁËË÷Òý±êʶ£¬ÈçÏÂËùʾ£º
#define ITIMER_REAL 0
#define ITIMER_VIRTUAL 1
#define ITIMER_PROF 2
7£®7£®1 Êý¾Ý½á¹¹itimerval
ËäÈ»£¬ÔÚÄÚºËÖмä¸ô¶¨Ê±Æ÷µÄ¼ä¸ô¼ÆÊýÆ÷ÊÇÒÔʱÖӵδð´ÎÊýΪµ¥Î»£¬µ«ÊÇÈÃÓû§ÒÔʱÖӵδðΪµ¥Î»À´Ö¸¶¨¼ä¸ô¶¨Ê±Æ÷µÄ¼ä¸ô¼ÆÊýÆ÷µÄ³õÖµÏÔÈ»ÊDz»Ì«·½±ãµÄ£¬ÒòΪÓû§Ï°¹ßµÄʱ¼äµ¥Î»ÊÇÃë¡¢ºÁÃë»ò΢ÃëµÈ¡£ËùÒÔLinux¶¨ÒåÁËÊý¾Ý½á¹¹itimervalÀ´ÈÃÓû§ÒÔÃë»ò΢ÃëΪµ¥Î»Ö¸¶¨¼ä¸ô¶¨Ê±Æ÷µÄʱ¼ä¼ä¸ôÖµ¡£Æ䶨ÒåÈçÏ£¨include/linux/time.h£©£º
struct itimerval {
struct timeval it_interval; /* timer interval */
struct timeval it_value; /* current value */
};
ÆäÖУ¬it_interval³ÉÔ±±íʾ¼ä¸ô¼ÆÊýÆ÷µÄ³õʼֵ£¬¶øit_value³ÉÔ±±íʾ¼ä¸ô¼ÆÊýÆ÷µÄµ±Ç°Öµ¡£ÕâÁ½¸ö³ÉÔ±¶¼ÊÇtimeval½á¹¹ÀàÐ͵ıäÁ¿£¬Òò´ËÆ侫¶È¿ÉÒԴﵽ΢Ã뼶¡£
l timevalÓëjiffiesÖ®¼äµÄÏ໥ת»»
ÓÉÓÚ¼ä¸ô¶¨Ê±Æ÷µÄ¼ä¸ô¼ÆÊýÆ÷µÄÄÚ²¿±íʾ·½Ê½ÓëÍⲿ±íÏÖ·½Ê½»¥²»Ïàͬ£¬Òò´ËÓбØҪʵÏÖÒÔ΢ÃëΪµ¥Î»µÄtimeval½á¹¹ºÍΪʱÖӵδð´ÎÊýµ¥Î»µÄjiffiesÖ®¼äµÄÏ໥ת»»¡£Îª´Ë£¬LinuxÔÚkernel/itimer.cÖÐʵÏÖÁËÁ½¸öº¯ÊýʵÏÖ¶þÕߵĻ¥Ïàת»»----tvtojiffies()º¯ÊýºÍjiffiestotv()º¯Êý¡£ËüÃǵÄÔ´ÂëÈçÏ£º
static unsigned long tvtojiffies(struct timeval *value)
{
unsigned long sec = (unsigned) value->tv_sec;
unsigned long usec = (unsigned) value->tv_usec;
if (sec > (ULONG_MAX / HZ))
return ULONG_MAX;
usec += 1000000 / HZ - 1;
usec /= 1000000 / HZ;
return HZ*sec+usec;
}
static void jiffiestotv(unsigned long jiffies, struct timeval *value)
{
value->tv_usec = (jiffies % HZ) * (1000000 / HZ);
value->tv_sec = jiffies / HZ;
}
7£®7£®2 Õæʵ¼ä¸ô¶¨Ê±Æ÷ITIMER_REALµÄµ×²ãÔËÐлúÖÆ
¼ä¸ô¶¨Ê±Æ÷ITIMER_VIRTºÍITIMER_PROFµÄµ×²ãÔËÐлúÖÆÊÇ·Ö±ðͨ¹ýº¯Êýdo_it_virt£¨£©º¯ÊýºÍdo_it_prof£¨£©º¯ÊýÀ´ÊµÏֵģ¬ÕâÀï¾Í²»ÔÙÖØÊö£¨¿ÉÒԲμû7.4.3½Ú£©¡£
ÓÉÓÚ¼ä¸ô¶¨Ê±Æ÷ITIMER_REAL±¾ÖÊÉÏÓëÄں˶¯Ì¬¶¨Ê±Æ÷²¢ÎÞÇø±ð¡£Òò´ËÄÚºËʵ¼ÊÉÏÊÇͨ¹ýÄں˶¯Ì¬¶¨Ê±Æ÷À´ÊµÏÖ½ø³ÌµÄITIMER_REAL¼ä¸ô¶¨Ê±Æ÷µÄ¡£Îª´Ë£¬task_struct½á¹¹ÖÐרÃÅÉèÁ¢Ò»¸ötimer_list½á¹¹ÀàÐ͵ijÉÔ±±äÁ¿real_timer¡£¶¯Ì¬¶¨Ê±Æ÷real_timerµÄº¯ÊýÖ¸Õëfunction×ÜÊDZ»task_struct½á¹¹µÄ³õʼ»¯ºêINIT_TASKÉèÖÃΪָÏòº¯Êýit_real_fn()¡£ÈçÏÂËùʾ£¨include/linux/sched.h£©£º
#define INIT_TASK(tsk) \
¡¡
real_timer£º {
function£º it_real_fn \
} \
¡¡
}
¶øreal_timerÁ´±íÔªËØlistºÍdata³ÉÔ±×ÜÊDZ»½ø³Ì´´½¨Ê±·Ö±ð³õʼ»¯Îª¿ÕºÍ½ø³Ìtask_struct½á¹¹µÄµØÖ·£¬ÈçÏÂËùʾ£¨kernel/fork.c£©£º
int do_fork(¡¡)
{
¡¡
p->it_real_value = p->it_virt_value = p->it_prof_value = 0;
p->it_real_incr = p->it_virt_incr = p->it_prof_incr = 0;
init_timer(&p->real_timer);
p->real_timer.data = (unsigned long)p;
¡¡
}
µ±Óû§Í¨¹ýsetitimer()ϵͳµ÷ÓÃÀ´ÉèÖýø³ÌµÄITIMER_REAL¼ä¸ô¶¨Ê±Æ÷ʱ£¬it_real_incr±»ÉèÖóɷÇÁãÖµ£¬ÓÚÊǸÃϵͳµ÷ÓÃÏàÓ¦µØÉèÖúÃreal_timer.expiresÖµ£¬È»ºó½ø³ÌµÄreal_timer¶¨Ê±Æ÷¾Í±»¼ÓÈëµ½Äں˶¯Ì¬¶¨Ê±Æ÷Á´±íÖУ¬ÕâÑù¸Ã½ø³ÌµÄITIMER_REAL¼ä¸ô¶¨Ê±Æ÷¾Í±»Æô¶¯ÁË¡£µ±real_timer¶¨Ê±Æ÷µ½ÆÚʱ£¬ËüµÄ¹ØÁªº¯Êýit_real_fn()½«±»Ö´ÐС£×¢Ò⣡ËùÓнø³ÌµÄreal_timer¶¨Ê±Æ÷µÄfunctionº¯ÊýÖ¸Õ붼ָÏòit_real_fn()Õâͬһ¸öº¯Êý£¬Òò´Ëit_real_fn()º¯Êý±ØÐëͨ¹ýÆä²ÎÊýÀ´Ê¶±ðÊÇÄÄÒ»¸ö½ø³Ì£¬Îª´ËËü½«unsigned longÀàÐ͵IJÎÊýp½âÊÍΪ½ø³Ìtask_struct½á¹¹µÄµØÖ·¡£¸Ãº¯ÊýµÄÔ´ÂëÈçÏ£¨kernel/itimer.c£©£º
void it_real_fn(unsigned long __data)
{
struct task_struct * p = (struct task_struct *) __data;
unsigned long interval;
send_sig(SIGALRM, p, 1);
interval = p->it_real_incr;
if (interval) {
if (interval > (unsigned long) LONG_MAX)
interval = LONG_MAX;
p->real_timer.expires = jiffies + interval;
add_timer(&p->real_timer);
}
}
º¯Êýit_real_fn()µÄÖ´Ðйý³Ì´óÖÂÈçÏ£º
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£¨2£©Ïò½ø³Ì·¢ËÍSIGALRMÐźš£
£¨3£©ÔÚ½ø³ÌµÄit_real_incr·Ç0µÄÇé¿öϼÌÐøÆô¶¯real_timer¶¨Ê±Æ÷¡£Ê×ÏÈ£¬¼ÆËãreal_timer¶¨Ê±Æ÷µÄexpiresֵΪ£¨jiffies£«it_real_incr£©¡£È»ºó£¬µ÷ÓÃadd_timer()º¯Êý½«real_timer¼ÓÈëµ½Äں˶¯Ì¬¶¨Ê±Æ÷Á´±íÖС£
7£®7£®3 itimer¶¨Ê±Æ÷µÄϵͳµ÷ÓÃ
Óëitimer¶¨Ê±Æ÷Ïà¹ØµÄsyscallÓÐÁ½¸ö£ºgetitimer()ºÍsetitimer()¡£ÆäÖУ¬getitimer()ÓÃÓÚ²éѯµ÷Óýø³ÌµÄÈý¸ö¼ä¸ô¶¨Ê±Æ÷µÄÐÅÏ¢£¬¶øsetitimer()ÔòÓÃÀ´ÉèÖõ÷Óýø³ÌµÄÈý¸ö¼ä¸ô¶¨Ê±Æ÷¡£ÕâÁ½¸ösyscall¶¼ÊÇÏÖÔÚkernel/itimer.cÎļþÖС£
7£®7£®3£®1 getitimer()ϵͳµ÷ÓõÄʵÏÖ
º¯Êýsys_getitimer()ÓÐÁ½¸ö²ÎÊý£º£¨1£©which£¬Ö¸¶¨²éѯµ÷Óýø³ÌµÄÄÄÒ»¸ö¼ä¸ô¶¨Ê±Æ÷£¬ÆäÈ¡Öµ¿ÉÒÔÊÇITIMER_REAL¡¢ITIMER_VIRTºÍITIMER_PROFÈýÕßÖ®Ò»¡££¨2£©valueÖ¸Õ룬ָÏòÓû§¿Õ¼äÖеÄÒ»¸öitimerval½á¹¹£¬ÓÃÓÚ½ÓÊÕ²éѯ½á¹û¡£¸Ãº¯ÊýµÄÔ´ÂëÈçÏ£º
/* SMP: Only we modify our itimer values. */
asmlinkage long sys_getitimer(int which, struct itimerval *value)
{
int error = -EFAULT;
struct itimerval get_buffer;
if (value) {
error = do_getitimer(which, &get_buffer);
if (!error &&
copy_to_user(value, &get_buffer, sizeof(get_buffer)))
error = -EFAULT;
}
return error;
}
ÏÔÈ»£¬sys_getitimer()º¯ÊýÖ÷Ҫͨ¹ýdo_getitimer()º¯ÊýÀ´²éѯµ±Ç°½ø³ÌµÄ¼ä¸ô¶¨Ê±Æ÷ÐÅÏ¢£¬²¢½«²éѯ½á¹û±£´æÔÚÄں˿ռäµÄ½á¹¹±äÁ¿get_bufferÖС£È»ºó£¬µ÷ÓÃcopy_to_usr()ºê½«get_bufferÖнá¹û¿½±´µ½Óû§¿Õ¼ä»º³åÇøÖС£
º¯Êýdo_getitimer()µÄÔ´ÂëÈçÏ£¨kernel/itimer.c£©£º
int do_getitimer(int which, struct itimerval *value)
{
register unsigned long val, interval;
switch (which) {
case ITIMER_REAL:
interval = current->it_real_incr;
val = 0;
/*
* FIXME! This needs to be atomic, in case the kernel timer happens!
*/
if (timer_pending(¤t->real_timer)) {
val = current->real_timer.expires - jiffies;
/* look out for negative/zero itimer.. */
if ((long) val <= 0)
val = 1;
}
break;
case ITIMER_VIRTUAL:
val = current->it_virt_value;
interval = current->it_virt_incr;
break;
case ITIMER_PROF:
val = current->it_prof_value;
interval = current->it_prof_incr;
break;
default:
return(-EINVAL);
}
jiffiestotv(val, &value->it_value);
jiffiestotv(interval, &value->it_interval);
return 0;
}
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º¯Êýsys_setitimer()²»½öÉèÖõ÷Óýø³ÌµÄÖ¸¶¨¼ä¸ô¶¨Ê±Æ÷£¬¶øÇÒ»¹·µ»Ø¸Ã¼ä¸ô¶¨Ê±Æ÷µÄÔÓÐÐÅÏ¢¡£ËüÓÐÈý¸ö²ÎÊý£º£¨1£©which£¬º¬ÒåÓësys_getitimer()ÖеIJÎÊýÏàͬ¡££¨2£©ÊäÈë²ÎÊývalue£¬Ö¸ÏòÓû§¿Õ¼äÖеÄÒ»¸öitimerval½á¹¹£¬º¬ÓдýÉèÖõÄÐÂÖµ¡££¨3£©Êä³ö²ÎÊýovalue£¬Ö¸ÏòÓû§¿Õ¼äÖеÄÒ»¸öitimerval½á¹¹£¬ÓÃÓÚ½ÓÊÕ¼ä¸ô¶¨Ê±Æ÷µÄÔÓÐÐÅÏ¢¡£
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/* SMP: Again, only we play with our itimers, and signals are SMP safe
* now so that is not an issue at all anymore.
*/
asmlinkage long sys_setitimer(int which, struct itimerval *value,
struct itimerval *ovalue)
{
struct itimerval set_buffer, get_buffer;
int error;
if (value) {
if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
return -EFAULT;
} else
memset((char *) &set_buffer, 0, sizeof(set_buffer));
error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : 0);
if (error || !ovalue)
return error;
if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
return -EFAULT;
return 0;
}
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£¨2£©µ÷ÓÃdo_setitimer()º¯ÊýÍê³Éʵ¼ÊµÄÉèÖòÙ×÷¡£Èç¹ûÊä³ö²ÎÊýovalueÖ¸ÕëÓÐЧ£¬ÔòÒÔÄں˱äÁ¿get_bufferµÄµØÖ·×÷Ϊdo_setitimer()º¯ÊýµÄµÚÈýÄǸöµ÷ÓòÎÊý£¬ÕâÑùµ±do_setitimer()º¯Êý·µ»Øʱ£¬get_buffer½á¹¹±äÁ¿Öоͽ«º¬Óе±Ç°½ø³ÌµÄÖ¸¶¨¼ä¸ô¶¨Ê±Æ÷µÄÔÀ´ÐÅÏ¢¡£Do_setitimer()º¯Êý·µ»Ø0Öµ±íʾ³É¹¦£¬·Ç0Öµ±íʾʧ°Ü¡£
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int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
{
register unsigned long i, j;
int k;
i = tvtojiffies(&value->it_interval);
j = tvtojiffies(&value->it_value);
if (ovalue && (k = do_getitimer(which, ovalue)) < 0)
return k;
switch (which) {
case ITIMER_REAL:
del_timer_sync(¤t->real_timer);
current->it_real_value = j;
current->it_real_incr = i;
if (!j)
break;
if (j > (unsigned long) LONG_MAX)
j = LONG_MAX;
i = j + jiffies;
current->real_timer.expires = i;
add_timer(¤t->real_timer);
break;
case ITIMER_VIRTUAL:
if (j)
j++;
current->it_virt_value = j;
current->it_virt_incr = i;
break;
case ITIMER_PROF:
if (j)
j++;
current->it_prof_value = j;
current->it_prof_incr = i;
break;
default:
return -EINVAL;
}
return 0;
}
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ϵͳµ÷ÓÃalarm¿ÉÒÔÈõ÷Óýø³ÌÔÚÖ¸¶¨µÄÃëÊý¼ä¸ôºóÊÕµ½Ò»¸öSIGALRMÐźš£ËüÖ»ÓÐÒ»¸ö²ÎÊýseconds£¬Ö¸¶¨ÒÔÃëÊý¼ÆµÄ¶¨Ê±¼ä¸ô¡£º¯Êýsys_alarm()µÄÔ´ÂëÈçÏ£¨kernel/timer.c£©£º
/*
* For backwards compatibility? This can be done in libc so Alpha
* and all newer ports shouldn't need it.
*/
asmlinkage unsigned long sys_alarm(unsigned int seconds)
{
struct itimerval it_new, it_old;
unsigned int oldalarm;
it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
it_new.it_value.tv_sec = seconds;
it_new.it_value.tv_usec = 0;
do_setitimer(ITIMER_REAL, &it_new, &it_old);
oldalarm = it_old.it_value.tv_sec;
/* ehhh.. We can't return 0 if we have an alarm pending.. */
/* And we'd better return too much than too little anyway */
if (it_old.it_value.tv_usec)
oldalarm++;
return oldalarm;
}
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LinuxÔÚinclude/linux/timer.hÍ·ÎļþÖж¨ÒåÁËÊý¾Ý½á¹¹timer_listÀ´ÃèÊöÒ»¸öÄں˶¨Ê±Æ÷£º
struct timer_list {
struct list_head list;
unsigned long expires;
unsigned long data;
void (*function)(unsigned long);
};
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static inline void init_timer(struct timer_list * timer)
{
timer->list.next = timer->list.prev = NULL;
}
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static inline int timer_pending (const struct timer_list * timer)
{
return timer->list.next != NULL;
}
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#define time_after(a,b) ((long)(b) - (long)(a) < 0)
#define time_before(a,b) time_after(b,a)
#define time_after_eq(a,b) ((long)(a) - (long)(b) >= 0)
#define time_before_eq(a,b) time_after_eq(b,a)
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/*
* Event timer code
*/
#define TVN_BITS 6
#define TVR_BITS 8
#define TVN_SIZE (1 << TVN_BITS)
#define TVR_SIZE (1 << TVR_BITS)
#define TVN_MASK (TVN_SIZE - 1)
#define TVR_MASK (TVR_SIZE - 1)
struct timer_vec {
int index;
struct list_head vec[TVN_SIZE];
};
struct timer_vec_root {
int index;
struct list_head vec[TVR_SIZE];
};
static struct timer_vec tv5;
static struct timer_vec tv4;
static struct timer_vec tv3;
static struct timer_vec tv2;
static struct timer_vec_root tv1;
static struct timer_vec * const tvecs[] = {
(struct timer_vec *)&tv1, &tv2, &tv3, &tv4, &tv5
};
#define NOOF_TVECS (sizeof(tvecs) / sizeof(tvecs[0]))
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º¯Êýinit_timervecs()ʵÏÖ¶Ô¶¯Ì¬¶¨Ê±Æ÷»úÖƵijõʼ»¯¡£¸Ãº¯Êý½ö±»sched_init()³õʼ»¯Àý³ÌËùµ÷Ó᣶¯Ì¬¶¨Ê±Æ÷»úÖƳõʼ»¯¹ý³ÌµÄÖ÷ÒªÈÎÎñ¾ÍÊǽ«tv1¡¢tv2¡¢¡¡¢tv5Õâ5¸ö½á¹¹±äÁ¿ÖеĶ¨Ê±Æ÷ÏòÁ¿Ö¸ÕëÊý×évec£Û£Ý³õʼ»¯ÎªNULL¡£ÈçÏÂËùʾ£¨kernel/timer.c£©£º
void init_timervecs (void)
{
int i;
for (i = 0; i < TVN_SIZE; i++) {
INIT_LIST_HEAD(tv5.vec + i);
INIT_LIST_HEAD(tv4.vec + i);
INIT_LIST_HEAD(tv3.vec + i);
INIT_LIST_HEAD(tv2.vec + i);
}
for (i = 0; i < TVR_SIZE; i++)
INIT_LIST_HEAD(tv1.vec + i);
}
ÉÏÊöº¯ÊýÖеĺêTVN_SIZEÊÇÖ¸timer_vec½á¹¹ÀàÐÍÖеĶ¨Ê±Æ÷ÏòÁ¿Ö¸ÕëÊý×évec£Û£ÝµÄ´óС£¬ÖµÎª64¡£ºêTVR_SIZEÊÇÖ¸timer_vec_root½á¹¹ÀàÐÍÖеĶ¨Ê±Æ÷ÏòÁ¿Êý×évec£Û£ÝµÄ´óС£¬ÖµÎª256¡£
7£®6£®3£®2 ¶¯Ì¬¶¨Ê±Æ÷µÄʱÖӵδð»ù×¼timer_jiffies
ÓÉÓÚ¶¯Ì¬¶¨Ê±Æ÷ÊÇÔÚʱÖÓÖжϵÄBottom HalfÖб»Ö´Ðеģ¬¶ø´ÓTIMER_BHÏòÁ¿±»¼¤»îµ½Æätimer_bh()º¯ÊýÕæÕýÖ´ÐÐÕâ¶Îʱ¼äÄÚ¿ÉÄÜ»áÓм¸´ÎʱÖÓÖжϷ¢Éú¡£Òò´ËÄں˱ØÐë¼ÇסÉÏÒ»´ÎÔËÐж¨Ê±Æ÷»úÖÆÊÇʲôʱºò£¬Ò²¼´Äں˱ØÐë±£´æÉÏÒ»´ÎÔËÐж¨Ê±Æ÷»úÖÆʱµÄjiffiesÖµ¡£Îª´Ë£¬LinuxÔÚkernel/timer.cÎļþÖж¨ÒåÁËÈ«¾Ö±äÁ¿timer_jiffiesÀ´±íʾÉÏÒ»´ÎÔËÐж¨Ê±Æ÷»úÖÆʱµÄjiffiesÖµ¡£¸Ã±äÁ¿µÄ¶¨ÒåÈçÏÂËùʾ£º
static unsigned long timer_jiffies;
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/* Initialize both explicitly - let's try to have them in the same cache line */
spinlock_t timerlist_lock = SPIN_LOCK_UNLOCKED;
7£®6£®3£®4 ½«Ò»¸ö¶¨Ê±Æ÷²åÈëµ½Á´±íÖÐ
º¯Êýadd_timer()ÓÃÀ´½«²ÎÊýtimerÖ¸ÕëËùÖ¸ÏòµÄ¶¨Ê±Æ÷²åÈëµ½Ò»¸öºÏÊʵĶ¨Ê±Æ÷Á´±íÖС£ËüÊ×Ïȵ÷ÓÃtimer_pending()º¯ÊýÅжÏËùÖ¸¶¨µÄ¶¨Ê±Æ÷ÊÇ·ñÒѾλÓÚÔÚij¸ö¶¨Ê±Æ÷ÏòÁ¿ÖеȴýÖ´ÐС£Èç¹ûÊÇ£¬Ôò²»½øÐÐÈκβÙ×÷£¬Ö»ÊÇ´òÓ¡Ò»ÌõÄں˸澯ÐÅÏ¢¾Í·µ»ØÁË£»Èç¹û²»ÊÇ£¬Ôòµ÷ÓÃinternal_add_timer()º¯ÊýÍê³Éʵ¼ÊµÄ²åÈë²Ù×÷¡£ÆäÔ´ÂëÈçÏ£¨kernel/timer.c£©£º
void add_timer(struct timer_list *timer)
{
unsigned long flags;
spin_lock_irqsave(&timerlist_lock, flags);
if (timer_pending(timer))
goto bug;
internal_add_timer(timer);
spin_unlock_irqrestore(&timerlist_lock, flags);
return;
bug:
spin_unlock_irqrestore(&timerlist_lock, flags);
printk("bug: kernel timer added twice at %p.\n",
__builtin_return_address(0));
}
º¯Êýinternal_add_timer()ÓÃÓÚ½«Ò»¸ö²»´¦ÓÚÈκζ¨Ê±Æ÷ÏòÁ¿ÖеĶ¨Ê±Æ÷²åÈëµ½ËüÓ¦¸ÃËù´¦µÄ¶¨Ê±Æ÷ÏòÁ¿ÖÐÈ¥£¨¸ù¾Ý¶¨Ê±Æ÷µÄexpiresÖµÀ´¾ö¶¨£©¡£ÈçÏÂËùʾ£¨kernel/timer.c£©£º
static inline void internal_add_timer(struct timer_list *timer)
{
/*
* must be cli-ed when calling this
*/
unsigned long expires = timer->expires;
unsigned long idx = expires - timer_jiffies;
struct list_head * vec;
if (idx < TVR_SIZE) {
int i = expires & TVR_MASK;
vec = tv1.vec + i;
} else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
int i = (expires >> TVR_BITS) & TVN_MASK;
vec = tv2.vec + i;
} else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
vec = tv3.vec + i;
} else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
vec = tv4.vec + i;
} else if ((signed long) idx < 0) {
/* can happen if you add a timer with expires == jiffies,
* or you set a timer to go off in the past
*/
vec = tv1.vec + tv1.index;
} else if (idx <= 0xffffffffUL) {
int i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
vec = tv5.vec + i;
} else {
/* Can only get here on architectures with 64-bit jiffies */
INIT_LIST_HEAD(&timer->list);
return;
}
/*
* Timers are FIFO!
*/
list_add(&timer->list, vec->prev);
}
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£¨3£©×îºó£¬µ÷ÓÃlist_add()º¯Êý½«¶¨Ê±Æ÷²åÈëµ½vecÖ¸ÕëËùÖ¸ÏòµÄ¶¨Ê±Æ÷¶ÓÁеÄβ²¿¡£
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µ±Ò»¸ö¶¨Ê±Æ÷ÒѾ±»²åÈëµ½Äں˶¯Ì¬¶¨Ê±Æ÷Á´±íÖкó£¬ÎÒÃÇ»¹¿ÉÒÔÐ޸ĸö¨Ê±Æ÷µÄexpiresÖµ¡£º¯Êýmod_timer()ʵÏÖÕâÒ»µã¡£ÈçÏÂËùʾ£¨kernel/timer.c£©£º
int mod_timer(struct timer_list *timer, unsigned long expires)
{
int ret;
unsigned long flags;
spin_lock_irqsave(&timerlist_lock, flags);
timer->expires = expires;
ret = detach_timer(timer);
internal_add_timer(timer);
spin_unlock_irqrestore(&timerlist_lock, flags);
return ret;
}
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º¯Êýdetach_timer()Ê×Ïȵ÷ÓÃtimer_pending()À´ÅжÏÖ¸¶¨µÄ¶¨Ê±Æ÷ÊÇ·ñÒѾ´¦ÓÚij¸öÁ´±íÖУ¬Èç¹û¶¨Ê±Æ÷ÔÀ´¾Í²»´¦ÓÚÈκÎÁ´±íÖУ¬Ôòdetach_timer()º¯ÊýʲôҲ²»×ö£¬Ö±½Ó·µ»Ø0Öµ£¬±íʾʧ°Ü¡£·ñÔò£¬¾Íµ÷ÓÃlist_del()º¯Êý½«¶¨Ê±Æ÷´ÓËüÔÀ´Ëù´¦µÄÁ´±íÖÐÕª³ý¡£ÈçÏÂËùʾ£¨kernel/timer.c£©£º
static inline int detach_timer (struct timer_list *timer)
{
if (!timer_pending(timer))
return 0;
list_del(&timer->list);
return 1;
}
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º¯Êýdel_timer()ÓÃÀ´½«Ò»¸ö¶¨Ê±Æ÷´ÓÏàÓ¦µÄÄں˶¨Ê±Æ÷¶ÓÁÐÖÐɾ³ý¡£¸Ãº¯Êýʵ¼ÊÉÏÊǶÔdetach_timer()º¯ÊýµÄ¸ß²ã·â×°¡£ÈçÏÂËùʾ£¨kernel/timer.c£©£º
int del_timer(struct timer_list * timer)
{
int ret;
unsigned long flags;
spin_lock_irqsave(&timerlist_lock, flags);
ret = detach_timer(timer);
timer->list.next = timer->list.prev = NULL;
spin_unlock_irqrestore(&timerlist_lock, flags);
return ret;
}
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º¯Êýcascade_timers()Íê³ÉÕâÖÖ¶¨Ê±Æ÷ǨÒƲÙ×÷£¬¸Ãº¯ÊýÖ»ÓÐÒ»¸ötimer_vec½á¹¹ÀàÐÍÖ¸ÕëµÄ²ÎÊýtv¡£Õâ¸öº¯Êý½«°Ñ¶¨Ê±Æ÷ÏòÁ¿tv->vec£Ûtv->index£ÝÖеÄËùÓж¨Ê±Æ÷ÖØÐÂÌî³äµ½ÉÏÒ»²ã¶¨Ê±Æ÷ÏòÁ¿ÖÐÈ¥¡£ÈçÏÂËùʾ£¨kernel/timer.c£©£º
static inline void cascade_timers(struct timer_vec *tv)
{
/* cascade all the timers from tv up one level */
struct list_head *head, *curr, *next;
head = tv->vec + tv->index;
curr = head->next;
/*
* We are removing _all_ timers from the list, so we don't have to
* detach them individually, just clear the list afterwards.
*/
while (curr != head) {
struct timer_list *tmp;
tmp = list_entry(curr, struct timer_list, list);
next = curr->next;
list_del(curr); // not needed
internal_add_timer(tmp);
curr = next;
}
INIT_LIST_HEAD(head);
tv->index = (tv->index + 1) & TVN_MASK;
}
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º¯Êýrun_timer_list()Íê³ÉÕâ¸ö¹¦ÄÜ¡£ÈçÇ°ËùÊö£¬¸Ãº¯ÊýÊDZ»timer_bh()º¯ÊýËùµ÷Óõģ¬Òò´ËÄں˶¨Ê±Æ÷ÊÇÔÚʱÖÓÖжϵÄBottom HalfÖб»Ö´Ðеġ£¼ÇסÕâÒ»µã·Ç³£ÖØÒª¡£È«¾Ö±äÁ¿timer_jiffies±íʾÁËÄÚºËÉÏÒ»´ÎÖ´ÐÐrun_timer_list()º¯ÊýµÄʱ¼ä£¬Òò´ËjiffiesÓëtimer_jiffiesµÄ²îÖµ¾Í±íʾÁË×Ô´ÓÉÏÒ»´Î´¦Àí¶¨Ê±Æ÷ÒÔÀ´£¬ÆÚ¼äÒ»¹²·¢ÉúÁ˶àÉÙ´ÎʱÖÓÖжϣ¬ÏÔÈ»run_timer_list()º¯Êý±ØÐëΪÆÚ¼äËù·¢ÉúµÄÿһ´ÎʱÖÓÖжϲ¹É϶¨Ê±Æ÷·þÎñ¡£¸Ãº¯ÊýµÄÔ´ÂëÈçÏ£¨kernel/timer.c£©£º
static inline void run_timer_list(void)
{
spin_lock_irq(&timerlist_lock);
while ((long)(jiffies - timer_jiffies) >= 0) {
struct list_head *head, *curr;
if (!tv1.index) {
int n = 1;
do {
cascade_timers(tvecs[n]);
} while (tvecs[n]->index == 1 && ++n < NOOF_TVECS);
}
repeat:
head = tv1.vec + tv1.index;
curr = head->next;
if (curr != head) {
struct timer_list *timer;
void (*fn)(unsigned long);
unsigned long data;
timer = list_entry(curr, struct timer_list, list);
fn = timer->function;
data= timer->data;
detach_timer(timer);
timer->list.next = timer->list.prev = NULL;
timer_enter(timer);
spin_unlock_irq(&timerlist_lock);
fn(data);
spin_lock_irq(&timerlist_lock);
timer_exit();
goto repeat;
}
++timer_jiffies;
tv1.index = (tv1.index + 1) & TVR_MASK;
}
spin_unlock_irq(&timerlist_lock);
}
º¯Êýrun_timer_list()µÄÖ´Ðйý³ÌÖ÷Òª¾ÍÊÇÓÃÒ»¸ö´ówhile{}Ñ»·À´ÎªÊ±ÖÓÖжÏÖ´Ðж¨Ê±Æ÷·þÎñ£¬Ã¿Ò»´ÎÑ»··þÎñÒ»´ÎʱÖÓÖжϡ£Òò´ËÒ»¹²ÒªÖ´ÐУ¨jiffies£timer_jiffies£«1£©´ÎÑ»·¡£Ñ»·ÌåËùÖ´ÐеķþÎñ²½ÖèÈçÏ£º
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void tqueue_bh(void)
{
run_task_queue(&tq_timer);
}
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DECLARE_TASK_QUEUE(tq_timer);
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void timer_bh(void)
{
update_times();
run_timer_list();
}
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/* jiffies at the most recent update of wall time */
unsigned long wall_jiffies;
¶øtimer_bh()º¯ÊýÕæÕýÖ´ÐÐʱµÄjiffiesÖµÓëwall_jiffiesµÄ²î¾ÍÊÇÔÚtimer_bh()ÕæÕýÖ´ÐÐ֮ǰËù·¢ÉúµÄʱÖÓÖжϴÎÊý¡£
º¯Êýupdate_times()µÄÔ´ÂëÈçÏ£¨kernel/timer.c£©£º
static inline void update_times(void)
{
unsigned long ticks;
/*
* update_times() is run from the raw timer_bh handler so we
* just know that the irqs are locally enabled and so we don't
* need to save/restore the flags of the local CPU here. -arca
*/
write_lock_irq(&xtime_lock);
ticks = jiffies - wall_jiffies;
if (ticks) {
wall_jiffies += ticks;
update_wall_time(ticks);
}
write_unlock_irq(&xtime_lock);
calc_load(ticks);
}
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º¯Êýupdate_wall_time()º¯Êý¸ù¾Ý²ÎÊýticksËùÖ¸¶¨µÄʱÖӵδð´ÎÊýÏàÓ¦µØ¸üÐÂÄÚºËÈ«¾Öʱ¼ä±äÁ¿xtime¡£ÆäÔ´ÂëÈçÏ£¨kernel/timer.c£©£º
/*
* Using a loop looks inefficient, but "ticks" is
* usually just one (we shouldn't be losing ticks,
* we're doing this this way mainly for interrupt
* latency reasons, not because we think we'll
* have lots of lost timer ticks
*/
static void update_wall_time(unsigned long ticks)
{
do {
ticks--;
update_wall_time_one_tick();
} while (ticks);
if (xtime.tv_usec >= 1000000) {
xtime.tv_usec -= 1000000;
xtime.tv_sec++;
second_overflow();
}
}
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º¯Êýupdate_wall_time_one_tick£¨£©ÓÃÀ´¸üÐÂÒ»´ÎʱÖӵδð¶Ôϵͳȫ¾Öʱ¼äxtimeµÄÓ°Ïì¡£ÓÉÓÚtickÈ«¾Ö±äÁ¿±íʾÁËÒ»´ÎʱÖӵδðµÄʱ¼ä¼ä¸ô³¤¶È£¨ÒÔusΪµ¥Î»£©£¬Òò´Ë¸Ãº¯ÊýµÄʵÏÖÖÐ×îºËÐĵĴúÂë¾ÍÊǽ«xtimeµÄtv_usec³ÉÔ±Ôö¼Ótick΢Ãë¡£ÕâÀïÎÒÃDz»È¥¹ØÐĺ¯ÊýʵÏÖÖÐÓëNTP£¨Network Time Protocol£©ºÍϵͳµ÷ÓÃadjtimex£¨£©µÄÏà¹Ø²¿·Ö¡£ÆäÔ´ÂëÈçÏ£¨kernel/timer.c£©£º
/* in the NTP reference this is called "hardclock()" */
static void update_wall_time_one_tick(void)
{
if ( (time_adjust_step = time_adjust) != 0 ) {
/* We are doing an adjtime thing.
*
* Prepare time_adjust_step to be within bounds.
* Note that a positive time_adjust means we want the clock
* to run faster.
*
* Limit the amount of the step to be in the range
* -tickadj .. +tickadj
*/
if (time_adjust > tickadj)
time_adjust_step = tickadj;
else if (time_adjust < -tickadj)
time_adjust_step = -tickadj;
/* Reduce by this step the amount of time left */
time_adjust -= time_adjust_step;
}
xtime.tv_usec += tick + time_adjust_step;
/*
* Advance the phase, once it gets to one microsecond, then
* advance the tick more.
*/
time_phase += time_adj;
if (time_phase <= -FINEUSEC) {
long ltemp = -time_phase >> SHIFT_SCALE;
time_phase += ltemp << SHIFT_SCALE;
xtime.tv_usec -= ltemp;
}
else if (time_phase >= FINEUSEC) {
long ltemp = time_phase >> SHIFT_SCALE;
time_phase -= ltemp << SHIFT_SCALE;
xtime.tv_usec += ltemp;
}
}
hfh08 ÓÚ 2006-08-21 00:25:25·¢±í:
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Linux¶ÔʱÖÓÖжϵijõʼ»¯ÊÇ·ÖΪ¼¸¸ö²½ÖèÀ´½øÐеģº£¨1£©Ê×ÏÈ£¬ÓÉinit_IRQ()º¯Êýͨ¹ýµ÷ÓÃinit_ISA_IRQ()º¯Êý¶ÔÖжÏÏòÁ¿32¡«256Ëù¶ÔÓ¦µÄÖжÏÏòÁ¿ÃèÊö·û½øÐгõʼ»¯ÉèÖá£ÏÔÈ»£¬ÕâÆäÖÐÒ²¾Í°ÑIRQ0£¨Ò²¼´ÖжÏÏòÁ¿32£©µÄÖжÏÏòÁ¿ÃèÊö·û³õʼ»¯ÁË¡££¨2£©È»ºó£¬init_IRQ()º¯ÊýÉèÖÃÖжÏÏòÁ¿32¡«256Ïà¶ÔÓ¦µÄÖжÏÃÅ¡££¨3£©init_IRQ()º¯Êý¶ÔPIT½øÐгõʼ»¯±à³Ì£»£¨4£©sched_init()º¯Êý¶Ô¼ÆÊýÆ÷¡¢Ê±¼äÖжϵÄBottom Half½øÐгõʼ»¯¡££¨5£©×îºó£¬ÓÉtime_init()º¯Êý¶ÔLinuxÄں˵ÄʱÖÓÖжϻúÖƽøÐгõʼ»¯¡£ÕâÈý¸ö³õʼ»¯º¯Êý¶¼ÊÇÓÉinit/main.cÎļþÖеÄstart_kernel()º¯Êýµ÷Óõģ¬ÈçÏ£º
asmlinkage void __init start_kernel()
{
¡
trap_init();
init_IRQ();
sched_init();
time_init();
softirq_init();
¡
}
(1)init_IRQ()º¯Êý¶Ô8254 PITµÄ³õʼ»¯±à³Ì
º¯Êýinit_IRQ()º¯ÊýÔÚÍê³ÉÖжÏÃŵijõʼ»¯ºó£¬¾Í¶Ô8254 PIT½øÐгõʼ»¯±à³ÌÉèÖã¬ÉèÖõIJ½ÖèÈçÏ£º£¨1£©ÉèÖÃ8254 PITµÄ¿ØÖƼĴæÆ÷£¨¶Ë¿Ú0x43£©µÄֵΪ¡°01100100¡±£¬Ò²¼´Ñ¡ÔñͨµÀ0¡¢ÏȶÁдLSBÔÙ¶ÁдMSB¡¢¹¤×÷ģʽ2¡¢¶þ½øÖÆ´æ´¢¸ñʽ¡££¨2£©½«ºêLATCHµÄֵдÈëͨµÀ0µÄ¼ÆÊýÆ÷ÖУ¨¶Ë¿Ú0x40£©£¬×¢ÒâÒªÏÈдLATCHµÄLSB£¬ÔÙдLATCHµÄ¸ß×Ö½Ú¡£ÆäÔ´ÂëÈçÏÂËùʾ£¨arch/i386/kernel/i8259.c£©£º
void __init init_IRQ(void)
{
¡¡
/*
* Set the clock to HZ Hz, we already have a valid
* vector now:
*/
outb_p(0x34,0x43); /* binary, mode 2, LSB/MSB, ch 0 */
outb_p(LATCH & 0xff , 0x40); /* LSB */
outb(LATCH >> 8 , 0x40); /* MSB */
¡¡
}
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º¯Êýsched_init()ÖÐÓëʱ¼äÏà¹ØµÄ³õʼ»¯¹ý³ÌÖ÷ÒªÓÐÁ½²½£º£¨1£©µ÷ÓÃinit_timervecs()º¯Êý³õʼ»¯Äں˶¨Ê±Æ÷»úÖÆ£»£¨2£©µ÷ÓÃinit_bh()º¯Êý½«BHÏòÁ¿TIMER_BH¡¢TQUEUE_BHºÍIMMEDIATE_BHËù¶ÔÓ¦µÄBHº¯Êý·Ö±ðÉèÖóÉtimer_bh()¡¢tqueue_bh()ºÍimmediate_bh()º¯Êý¡£ÈçÏÂËùʾ£¨kernel/sched.c£©£º
void __init sched_init(void)
{
¡¡
init_timervecs();
init_bh(TIMER_BH, timer_bh);
init_bh(TQUEUE_BH, tqueue_bh);
init_bh(IMMEDIATE_BH, immediate_bh);
¡¡
}
£¨3£©time_init()º¯Êý¶ÔÄÚºËʱÖÓÖжϻúÖƵijõʼ»¯
Ç°ÃæÁ½¸öº¯ÊýËù½øÐеijõʼ»¯²½Ö趼ÊÇΪʱ¼äÖжϻúÖÆ×öºÃ×¼±¸¶øÒÑ¡£ÔÚÖ´ÐÐÍêinit_IRQ()º¯ÊýºÍsched_init()º¯Êýºó£¬CPUÒѾ¿ÉÒÔΪIRQ0ÉϵÄʱÖÓÖжϽøÐзþÎñÁË£¬ÒòΪIRQ0Ëù¶ÔÓ¦µÄÖжÏÃÅÒѾ±»ÉèÖúÃÖ¸ÏòÖжϷþÎñº¯ÊýIRQ0x20_interrupt()¡£µ«ÊÇÓÉÓÚ´ËʱÖжÏÏòÁ¿0x20µÄÖжÏÏòÁ¿ÃèÊö·ûirq_desc£Û0£Ý»¹ÊÇ´¦ÓÚ³õʼ״̬£¨Æästatus³ÉÔ±µÄֵΪIRQ_DISABLED£©£¬²¢Î´¹Ò½ÓÈκξßÌåµÄÖжϷþÎñÃèÊö·û£¬Òò´ËÕâʱCPU¶ÔIRQ0µÄÖжϷþÎñ²¢Ã»ÓÐÈκξßÌåÒâÒ壬¶øÖ»ÊÇ°´Õչ涨µÄÁ÷³Ì¿ÕÅÜÒ»ÌË¡£µ«Êǵ±CPUÖ´ÐÐÍêtime_init()º¯Êýºó£¬ÇéÐξʹó²»Ò»ÑùÁË¡£
º¯Êýtime_init()Ö÷Òª×öÈý¼þÊ£º£¨1£©´ÓRTCÖлñÈ¡ÄÚºËÆô¶¯Ê±µÄʱ¼äÓëÈÕÆÚ£»£¨2£©ÔÚCPUÓÐTSCµÄÇé¿öÏÂУ׼TSC£¬ÒÔ±ãΪºóÃæʹÓÃTSC×öºÃ×¼±¸£»£¨3£©ÔÚIRQ0µÄÖжÏÇëÇóÃèÊö·ûÖйҽӾßÌåµÄÖжϷþÎñÃèÊö·û¡£ÆäÔ´ÂëÈçÏÂËùʾ£¨arch/i386/kernel/time.c£©£º
void __init time_init(void)
{
extern int x86_udelay_tsc;
xtime.tv_sec = get_cmos_time();
xtime.tv_usec = 0;
/*
* If we have APM enabled or the CPU clock speed is variable
* (CPU stops clock on HLT or slows clock to save power)
* then the TSC timestamps may diverge by up to 1 jiffy from
* 'real time' but nothing will break.
* The most frequent case is that the CPU is "woken" from a halt
* state by the timer interrupt itself, so we get 0 error. In the
* rare cases where a driver would "wake" the CPU and request a
* timestamp, the maximum error is < 1 jiffy. But timestamps are
* still perfectly ordered.
* Note that the TSC counter will be reset if APM suspends
* to disk; this won't break the kernel, though, 'cuz we're
* smart. See arch/i386/kernel/apm.c.
*/
/*
* Firstly we have to do a CPU check for chips with
* a potentially buggy TSC. At this point we haven't run
* the ident/bugs checks so we must run this hook as it
* may turn off the TSC flag.
*
* NOTE: this doesnt yet handle SMP 486 machines where only
* some CPU's have a TSC. Thats never worked and nobody has
* moaned if you have the only one in the world - you fix it!
*/
dodgy_tsc();
if (cpu_has_tsc) {
unsigned long tsc_quotient = calibrate_tsc();
if (tsc_quotient) {
fast_gettimeoffset_quotient = tsc_quotient;
use_tsc = 1;
/*
* We could be more selective here I suspect
* and just enable this for the next intel chips ?
*/
x86_udelay_tsc = 1;
#ifndef do_gettimeoffset
do_gettimeoffset = do_fast_gettimeoffset;
#endif
do_get_fast_time = do_gettimeofday;
/* report CPU clock rate in Hz.
* The formula is (10^6 * 2^32) / (2^32 * 1 / (clocks/us)) =
* clock/second. Our precision is about 100 ppm.
*/
{ unsigned long eax=0, edx=1000;
__asm__("divl %2"
:"=a" (cpu_khz), "=d" (edx)
:"r" (tsc_quotient),
"0" (eax), "1" (edx));
printk("Detected %lu.%03lu MHz processor.\n", cpu_khz / 1000, cpu_khz % 1000);
}
}
}
#ifdef CONFIG_VISWS
printk("Starting Cobalt Timer system clock\n");
/* Set the countdown value */
co_cpu_write(CO_CPU_TIMEVAL, CO_TIME_HZ/HZ);
/* Start the timer */
co_cpu_write(CO_CPU_CTRL, co_cpu_read(CO_CPU_CTRL) | CO_CTRL_TIMERUN);
/* Enable (unmask) the timer interrupt */
co_cpu_write(CO_CPU_CTRL, co_cpu_read(CO_CPU_CTRL) & ~CO_CTRL_TIMEMASK);
/* Wire cpu IDT entry to s/w handler (and Cobalt APIC to IDT) */
setup_irq(CO_IRQ_TIMER, &irq0);
#else
setup_irq(0, &irq0);
#endif
}
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/* Cached *multiplier* to convert TSC counts to microseconds.
* (see the equation below).
* Equal to 2^32 * (1 / (clocks per usec) ).
* Initialized in time_init.
*/
unsigned long fast_gettimeoffset_quotient;
¡¡
static int use_tsc;
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static struct irqaction irq0 = { timer_interrupt, SA_INTERRUPT, 0, "timer", NULL, NULL};
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7£®4£®2 ʱÖÓÖжϷþÎñÀý³Ìtimer_interrupt()
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º¯Êýtimer_interrupt()µÄÔ´ÂëÈçÏ£¨arch/i386/kernel/time.c£©£º
/*
* This is the same as the above, except we _also_ save the current
* Time Stamp Counter value at the time of the timer interrupt, so that
* we later on can estimate the time of day more exactly.
*/
static void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
int count;
/*
* Here we are in the timer irq handler. We just have irqs locally
* disabled but we don't know if the timer_bh is running on the other
* CPU. We need to avoid to SMP race with it. NOTE: we don' t need
* the irq version of write_lock because as just said we have irq
* locally disabled. -arca
*/
write_lock(&xtime_lock);
if (use_tsc)
{
/*
* It is important that these two operations happen almost at
* the same time. We do the RDTSC stuff first, since it's
* faster. To avoid any inconsistencies, we need interrupts
* disabled locally.
*/
/*
* Interrupts are just disabled locally since the timer irq
* has the SA_INTERRUPT flag set. -arca
*/
/* read Pentium cycle counter */
rdtscl(last_tsc_low);
spin_lock(&i8253_lock);
outb_p(0x00, 0x43); /* latch the count ASAP */
count = inb_p(0x40); /* read the latched count */
count |= inb(0x40) << 8;
spin_unlock(&i8253_lock);
count = ((LATCH-1) - count) * TICK_SIZE;
delay_at_last_interrupt = (count + LATCH/2) / LATCH;
}
do_timer_interrupt(irq, NULL, regs);
write_unlock(&xtime_lock);
}
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º¯Êýdo_timer_interrupt()µÄÔ´ÂëÈçÏ£¨arch/i386/kernel/time.c£©£º
/*
* timer_interrupt() needs to keep up the real-time clock,
* as well as call the "do_timer()" routine every clocktick
*/
static inline void do_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
¡£¡£¡£¡£¡£¡£
do_timer(regs);
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/*
* If we have an externally synchronized Linux clock, then update
* CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
* called as close as possible to 500 ms before the new second starts.
*/
if ((time_status & STA_UNSYNC) == 0 &&
xtime.tv_sec > last_rtc_update + 660 &&
xtime.tv_usec >= 500000 - ((unsigned) tick) / 2 &&
xtime.tv_usec <= 500000 + ((unsigned) tick) / 2) {
if (set_rtc_mmss(xtime.tv_sec) == 0)
last_rtc_update = xtime.tv_sec;
else
last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */
}
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}
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void do_timer(struct pt_regs *regs)
{
(*(unsigned long *)&jiffies)++;
#ifndef CONFIG_SMP
/* SMP process accounting uses the local APIC timer */
update_process_times(user_mode(regs));
#endif
mark_bh(TIMER_BH);
if (TQ_ACTIVE(tq_timer))
mark_bh(TQUEUE_BH);
}
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#ifdef __KERNEL__
#define user_mode(regs) ((VM_MASK & (regs)->eflags) || (3 & (regs)->xcs))
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#endif
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º¯Êýupdate_process_times()±»ÓÃÀ´ÔÚ·¢ÉúʱÖÓÖжÏʱ¸üе±Ç°½ø³ÌÒÔ¼°ÄÚºËÖÐÓëʱ¼äÏà¹ØµÄͳ¼ÆÐÅÏ¢£¬²¢¸ù¾ÝÕâЩÐÅÏ¢×÷³öÏàÓ¦µÄ¶¯×÷£¬±ÈÈ磺ÖØнøÐе÷¶È£¬Ïòµ±Ç°½ø³Ì·¢³öÐźŵȡ£¸Ãº¯Êý½öÓÐÒ»¸ö²ÎÊýuser_tick£¬È¡ÖµÎª1»ò0£¬Æ京ÒåÔÚÇ°ÃæÒѾÐðÊö¹ý¡£
¸Ãº¯ÊýµÄÔ´´úÂëÈçÏ£¨kernel/timer.c£©£º
/*
* Called from the timer interrupt handler to charge one tick to the current
* process. user_tick is 1 if the tick is user time, 0 for system.
*/
void update_process_times(int user_tick)
{
struct task_struct *p = current;
int cpu = smp_processor_id(), system = user_tick ^ 1;
update_one_process(p, user_tick, system, cpu);
if (p->pid) {
if (--p->counter <= 0) {
p->counter = 0;
p->need_resched = 1;
}
if (p->nice > 0)
kstat.per_cpu_nice[cpu] += user_tick;
else
kstat.per_cpu_user[cpu] += user_tick;
kstat.per_cpu_system[cpu] += system;
} else if (local_bh_count(cpu) || local_irq_count(cpu) > 1)
kstat.per_cpu_system[cpu] += system;
}
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l update_one_process()º¯Êý
ʵÏÖÔÚkernel/timer.cÎļþÖеÄupdate_one_process()º¯ÊýÓÃÀ´ÔÚʱÖÓÖжϷ¢Éúʱ¸üÐÂÒ»¸ö½ø³ÌµÄtask_struc½á¹¹ÖеÄʱ¼äͳ¼ÆÐÅÏ¢¡£ÆäÔ´ÂëÈçÏ£¨kernel/timer.c£©£º
void update_one_process(struct task_struct *p, unsigned long user,
unsigned long system, int cpu)
{
p->per_cpu_utime[cpu] += user;
p->per_cpu_stime[cpu] += system;
do_process_times(p, user, system);
do_it_virt(p, user);
do_it_prof(p);
}
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l do_process_times()º¯Êý
º¯Êýdo_process_times()½«¸üÐÂÖ¸¶¨½ø³ÌµÄ×Üʱ¼äͳ¼ÆÐÅÏ¢¡£Ã¿¸ö½ø³Ìtask_struct½á¹¹Öж¼ÓÐÒ»¸ö³ÉÔ±times£¬ËüÊÇÒ»¸ötms½á¹¹ÀàÐÍ£¨include/linux/times.h£©£º
struct tms {
clock_t tms_utime; £¯£ª ±¾½ø³ÌÔÚÓû§Ì¨ÏµÄÖ´ÐÐʱ¼ä×ÜºÍ £ª£¯
clock_t tms_stime; £¯£ª ±¾½ø³ÌÔÚºËÐÄ̬ϵÄÖ´ÐÐʱ¼ä×ÜºÍ £ª£¯
clock_t tms_cutime; £¯£ª ËùÓÐ×Ó½ø³ÌÔÚÓû§Ì¬ÏµÄÖ´ÐÐʱ¼ä×ÜºÍ £ª£¯
clock_t tms_cstime; £¯£ª ËùÓÐ×Ó½ø³ÌÔÚºËÐÄ̬ϵÄÖ´ÐÐʱ¼ä×ÜºÍ £ª£¯
};
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static inline void do_process_times(struct task_struct *p,
unsigned long user, unsigned long system)
{
unsigned long psecs;
psecs = (p->times.tms_utime += user);
psecs += (p->times.tms_stime += system);
if (psecs / HZ > p->rlim[RLIMIT_CPU].rlim_cur) {
/* Send SIGXCPU every second.. */
if (!(psecs % HZ))
send_sig(SIGXCPU, p, 1);
/* and SIGKILL when we go over max.. */
if (psecs / HZ > p->rlim[RLIMIT_CPU].rlim_max)
send_sig(SIGKILL, p, 1);
}
}
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l do_it_virt()º¯Êý
ÿ¸ö½ø³Ì¶¼ÓÐÒ»¸öÓû§Ì¬Ö´ÐÐʱ¼äµÄitimerÈí¼þ¶¨Ê±Æ÷¡£½ø³ÌÈÎÎñ½á¹¹task_structÖеÄit_virt_value³ÉÔ±ÊÇÕâ¸öÈí¼þ¶¨Ê±Æ÷µÄʱ¼ä¼ÆÊýÆ÷¡£µ±½ø³ÌÔÚÓû§Ì¬ÏÂÖ´ÐÐʱ£¬Ã¿Ò»´ÎʱÖӵδð¶¼Ê¹¼ÆÊýÆ÷it_virt_value¼õ1£¬µ±¼õµ½0ʱÄÚºËÏò½ø³Ì·¢ËÍSIGVTALRMÐźţ¬²¢ÖØÖóõÖµ¡£³õÖµ±£´æÔÚ½ø³ÌµÄtask_struct½á¹¹µÄit_virt_incr³ÉÔ±ÖС£
º¯Êýdo_it_virt()µÄÔ´ÂëÈçÏ£¨kernel/timer.c£©£º
static inline void do_it_virt(struct task_struct * p, unsigned long ticks)
{
unsigned long it_virt = p->it_virt_value;
if (it_virt) {
it_virt -= ticks;
if (!it_virt) {
it_virt = p->it_virt_incr;
send_sig(SIGVTALRM, p, 1);
}
p->it_virt_value = it_virt;
}
}
l do_it_prof£¨£©º¯Êý
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static inline void do_it_prof(struct task_struct *p)
{
unsigned long it_prof = p->it_prof_value;
if (it_prof) {
if (--it_prof == 0) {
it_prof = p->it_prof_incr;
send_sig(SIGPROF, p, 1);
}
p->it_prof_value = it_prof;
}
}
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#define CLOCK_TICK_RATE 1193180 /* Underlying HZ */
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#ifndef HZ
#define HZ 100
#endif
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long tick = (1000000 + HZ/2) / HZ; /* timer interrupt period */
tick±äÁ¿µÄµ¥Î»ÊÇ΢Ã¦Ìs£©£¬ÓÉÓÚÔÚ²»Í¬Æ½Ì¨ÉϺêHZµÄÖµ»áÓÐËù²»Í¬£¬Òò´Ë·½³Ìʽtick£½1000000¡ÂHZµÄ½á¹û¿ÉÄÜ»áÊǸöСÊý£¬Òò´Ë½«Æä½øÐÐËÄÉáÎåÈë³ÉÒ»¸öÕûÊý£¬ËùÒÔLinux½«tick¶¨Òå³É£¨1000000£«HZ£¯2£©£¯HZ£¬ÆäÖб»³ýÊý±í´ïʽÖеÄHZ£¯2µÄ×÷ÓþÍÊÇÓÃÀ´½«tickÖµÏòÉÏÔ²Õû³ÉÒ»¸öÕûÐÍÊý¡£
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#define TICK_SIZE tick
£¨5£©ºêLATCH£ºLinuxÓúêLATCHÀ´¶¨ÒåҪдµ½PITͨµÀ0µÄ¼ÆÊýÆ÷ÖеÄÖµ£¬Ëü±íʾPIT½«Ã»¸ô¶àÉÙ¸öʱÖÓÖÜÆÚ²úÉúÒ»´ÎʱÖÓÖжϡ£ÏÔÈ»LATCHÓ¦¸ÃÓÉÏÂÁй«Ê½¼ÆË㣺
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/* LATCH is used in the interval timer and ftape setup. */
#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
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unsigned long volatile jiffies;
CÓïÑÔÏÞ¶¨·ûvolatile±íʾjiffiesÊÇÒ»¸öÒ׸ñäµÄ±äÁ¿£¬Òò´Ë±àÒëÆ÷½«Ê¹¶Ô¸Ã±äÁ¿µÄ·ÃÎÊ´Ó²»Í¨¹ýCPUÄÚ²¿cacheÀ´½øÐС£
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struct timeval {
time_t tv_sec; /* seconds */
suseconds_t tv_usec; /* microseconds */
};
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/* The current time */
volatile struct timeval xtime __attribute__ ((aligned (16)));
µ«ÊÇ£¬È«¾Ö±äÁ¿xtimeËùά³ÖµÄµ±Ç°Ê±¼äͨ³£Êǹ©Óû§À´¼ìË÷ºÍÉèÖõģ¬¶øÆäËûÄÚºËÄ£¿éͨ³£ºÜÉÙʹÓÃËü£¨ÆäËûÄÚºËÄ£¿éÓõÃ×î¶àµÄÊÇjiffies£©£¬Òò´Ë¶ÔxtimeµÄ¸üв¢²»ÊÇÒ»Ïî½ôÆȵÄÈÎÎñ£¬ËùÒÔÕâÒ»¹¤×÷ͨ³£±»ÑÓ³Ùµ½Ê±ÖÓÖжϵĵװ벿·Ö£¨bottom half£©ÖÐÀ´½øÐС£ÓÉÓÚbottom halfµÄÖ´ÐÐʱ¼ä´øÓв»È·¶¨ÐÔ£¬Òò´ËΪÁ˼ÇסÄÚºËÉÏÒ»´Î¸üÐÂxtimeÊÇʲôʱºò£¬LinuxÄں˶¨ÒåÁËÒ»¸öÀàËÆÓÚjiffiesµÄÈ«¾Ö±äÁ¿wall_jiffies£¬À´±£´æÄÚºËÉÏÒ»´Î¸üÐÂxtimeʱµÄjiffiesÖµ¡£Ê±ÖÓÖжϵĵװ벿·Öÿһ´Î¸üÐÂxtimeµÄʱºî¶¼»á½«wall_jiffies¸üÐÂΪµ±Ê±µÄjiffiesÖµ¡£È«¾Ö±äÁ¿wall_jiffies¶¨ÒåÔÚkernel/timer.cÎļþÖУº
/* jiffies at the most recent update of wall time */
unsigned long wall_jiffies;
¢ÛÈ«¾Ö±äÁ¿sys_tz£ºËüÊÇÒ»¸ötimezone½á¹¹ÀàÐ͵ÄÈ«¾Ö±äÁ¿£¬±íʾϵͳµ±Ç°µÄʱÇøÐÅÏ¢¡£½á¹¹ÀàÐÍtimezone¶¨ÒåÔÚinclude/linux/time.hÍ·ÎļþÖУ¬ÈçÏÂËùʾ£º
struct timezone {
int tz_minuteswest; /* minutes west of Greenwich */
int tz_dsttime; /* type of dst correction */
};
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struct timezone sys_tz;
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static int use_tsc;
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#define rdtsc(low,high) \
__asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high))
#define rdtscl(low) \
__asm__ __volatile__ ("rdtsc" : "=a" (low) : : "edx")
#define rdtscll(val) \
__asm__ __volatile__ ("rdtsc" : "=A" (val))
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/* Cached *multiplier* to convert TSC counts to microseconds.
* (see the equation below).
* Equal to 2^32 * (1 / (clocks per usec) ).
* Initialized in time_init.
*/
unsigned long fast_gettimeoffset_quotient;
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/* Number of usecs that the last interrupt was delayed */
static int delay_at_last_interrupt;
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#ifndef RTC_PORT
#define RTC_PORT(x) (0x70 + (x))
#define RTC_ALWAYS_BCD 1 /* RTC operates in binary mode */
#endif
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#define CMOS_READ(addr) ({ \
outb_p((addr),RTC_PORT(0)); \
inb_p(RTC_PORT(1)); \
})
#define CMOS_WRITE(val, addr) ({ \
outb_p((addr),RTC_PORT(0)); \
outb_p((val),RTC_PORT(1)); \
})
#define RTC_IRQ 8
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#define RTC_SECONDS 0
#define RTC_SECONDS_ALARM 1
#define RTC_MINUTES 2
#define RTC_MINUTES_ALARM 3
#define RTC_HOURS 4
#define RTC_HOURS_ALARM 5
/* RTC_*_alarm is always true if 2 MSBs are set */
# define RTC_ALARM_DONT_CARE 0xC0
#define RTC_DAY_OF_WEEK 6
#define RTC_DAY_OF_MONTH 7
#define RTC_MONTH 8
#define RTC_YEAR 9
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#define RTC_REG_A 10
#define RTC_REG_B 11
#define RTC_REG_C 12
#define RTC_REG_D 13
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#define RTC_FREQ_SELECT RTC_REG_A
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# define RTC_UIP 0x80
# define RTC_DIV_CTL 0x70
/* Periodic intr. / Square wave rate select. 0=none, 1=32.8kHz,... 15=2Hz */
# define RTC_RATE_SELECT 0x0F
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/* divider control: refclock values 4.194 / 1.049 MHz / 32.768 kHz */
# define RTC_REF_CLCK_4MHZ 0x00
# define RTC_REF_CLCK_1MHZ 0x10
# define RTC_REF_CLCK_32KHZ 0x20
/* 2 values for divider stage reset, others for "testing purposes only" */
# define RTC_DIV_RESET1 0x60
# define RTC_DIV_RESET2 0x70
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#define RTC_CONTROL RTC_REG_B
# define RTC_SET 0x80 /* disable updates for clock setting */
# define RTC_PIE 0x40 /* periodic interrupt enable */
# define RTC_AIE 0x20 /* alarm interrupt enable */
# define RTC_UIE 0x10 /* update-finished interrupt enable */
# define RTC_SQWE 0x08 /* enable square-wave output */
# define RTC_DM_BINARY 0x04 /* all time/date values are BCD if clear */
# define RTC_24H 0x02 /* 24 hour mode - else hours bit 7 means pm */
# define RTC_DST_EN 0x01 /* auto switch DST - works f. USA only */
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#define RTC_INTR_FLAGS RTC_REG_C
/* caution - cleared by read */
# define RTC_IRQF 0x80 /* any of the following 3 is active */
# define RTC_PF 0x40
# define RTC_AF 0x20
# define RTC_UF 0x10
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#define RTC_VALID RTC_REG_D
# define RTC_VRT 0x80 /* valid RAM and time */
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#ifndef BCD_TO_BIN
#define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)
#endif
#ifndef BIN_TO_BCD
#define BIN_TO_BCD(val) ((val)=(((val)/10)<<4) + (val)%10)
#endif
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/* not static: needed by APM */
unsigned long get_cmos_time(void)
{
unsigned int year, mon, day, hour, min, sec;
int i;
/* The Linux interpretation of the CMOS clock register contents:
* When the Update-In-Progress (UIP) flag goes from 1 to 0, the
* RTC registers show the second which has precisely just started.
* Let's hope other operating systems interpret the RTC the same way.
*/
/* read RTC exactly on falling edge of update flag */
for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
break;
for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
break;
do { /* Isn't this overkill ? UIP above should guarantee consistency */
sec = CMOS_READ(RTC_SECONDS);
min = CMOS_READ(RTC_MINUTES);
hour = CMOS_READ(RTC_HOURS);
day = CMOS_READ(RTC_DAY_OF_MONTH);
mon = CMOS_READ(RTC_MONTH);
year = CMOS_READ(RTC_YEAR);
} while (sec != CMOS_READ(RTC_SECONDS));
if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
{
BCD_TO_BIN(sec);
BCD_TO_BIN(min);
BCD_TO_BIN(hour);
BCD_TO_BIN(day);
BCD_TO_BIN(mon);
BCD_TO_BIN(year);
}
if ((year += 1900) < 1970)
year += 100;
return mktime(year, mon, day, hour, min, sec);
}
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º¯Êýmktime()¶¨ÒåÔÚinclude/linux/time.hÍ·ÎļþÖУ¬ËüÓÃÀ´¸ù¾ÝGaussËã·¨½«ÒÔyear/mon/day/hour/min/sec£¨Èç1980£12£31 23£º59£º59£©¸ñʽ±íʾµÄʱ¼äת»»ÎªÏà¶ÔÓÚ1970£01£01 00£º00£º00Õâ¸öUNIXʱ¼ä»ù×¼ÒÔÀ´µÄÏà¶ÔÃëÊý¡£ÆäÔ´ÂëÈçÏ£º
static inline unsigned long
mktime (unsigned int year, unsigned int mon,
unsigned int day, unsigned int hour,
unsigned int min, unsigned int sec)
{
if (0 >= (int) (mon -= 2)) { /* 1..12 -> 11,12,1..10 */
mon += 12; /* Puts Feb last since it has leap day */
year -= 1;
}
return (((
(unsigned long) (year/4 - year/100 + year/400 + 367*mon/12 + day) +
year*365 - 719499
)*24 + hour /* now have hours */
)*60 + min /* now have minutes */
)*60 + sec; /* finally seconds */
}
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static int set_rtc_mmss(unsigned long nowtime)
{
int retval = 0;
int real_seconds, real_minutes, cmos_minutes;
unsigned char save_control, save_freq_select;
/* gets recalled with irq locally disabled */
spin_lock(&rtc_lock);
save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
cmos_minutes = CMOS_READ(RTC_MINUTES);
if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
BCD_TO_BIN(cmos_minutes);
/*
* since we're only adjusting minutes and seconds,
* don't interfere with hour overflow. This avoids
* messing with unknown time zones but requires your
* RTC not to be off by more than 15 minutes
*/
real_seconds = nowtime % 60;
real_minutes = nowtime / 60;
if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
real_minutes += 30; /* correct for half hour time zone */
real_minutes %= 60;
if (abs(real_minutes - cmos_minutes) < 30) {
if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
BIN_TO_BCD(real_seconds);
BIN_TO_BCD(real_minutes);
}
CMOS_WRITE(real_seconds,RTC_SECONDS);
CMOS_WRITE(real_minutes,RTC_MINUTES);
} else {
printk(KERN_WARNING
"set_rtc_mmss: can't update from %d to %d\n",
cmos_minutes, real_minutes);
retval = -1;
}
/* The following flags have to be released exactly in this order,
* otherwise the DS12887 (popular MC146818A clone with integrated
* battery and quartz) will not reset the oscillator and will not
* update precisely 500 ms later. You won't find this mentioned in
* the Dallas Semiconductor data sheets, but who believes data
* sheets anyway ... -- Markus Kuhn
*/
CMOS_WRITE(save_control, RTC_CONTROL);
CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
spin_unlock(&rtc_lock);
return retval;
}
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/* last time the cmos clock got updated */
static long last_rtc_update;
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