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Add clock_schedule(), a feature that allows realtime clock drivers to

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request that their clock_settime() methods be called at a given offset
from top-of-second.  This adds a timeout_task to the rtc_instance so that
each clock can be separately added to taskqueue_thread with the scheduling
it prefers, instead of looping through all the clocks at once with a
single task on taskqueue_thread.  If a driver doesn't call clock_schedule()
the default is the old behavior: clock_settime() is queued immediately.

The motivation behind this is that I was on the path of adding identical
code to a third RTC driver to figure out a delta to top-of-second and
sleep for that amount of time because writing the the RTC registers resets
the hardware's concept of top-of-second.  (Sometimes it's not top-of-second,
some RTC clocks tick over a half second after you set their time registers.)
Worst-case would be to sleep for almost a full second, which is a rude thing
to do on a shared task queue thread.
This commit is contained in:
Ian Lepore 2017-07-31 01:18:21 +00:00
parent d0f68f913b
commit cd9d9e5417
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=321745
2 changed files with 69 additions and 22 deletions
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77
sys/kern/subr_rtc.c
View File

@ -95,7 +95,10 @@ struct rtc_instance {
device_t clockdev;
int resolution;
int flags;
u_int schedns;
struct timespec resadj;
struct timeout_task
stask;
LIST_ENTRY(rtc_instance)
rtc_entries;
};
@ -104,7 +107,6 @@ struct rtc_instance {
* Clocks are updated using a task running on taskqueue_thread.
*/
static void settime_task_func(void *arg, int pending);
static struct task settime_task = TASK_INITIALIZER(0, settime_task_func, NULL);
/*
* Registered clocks are kept in a list which is sorted by resolution; the more
@ -116,9 +118,9 @@ static struct sx rtc_list_lock;
SX_SYSINIT(rtc_list_lock_init, &rtc_list_lock, "rtc list");
/*
* On the task thread, invoke the clock_settime() method of each registered
* clock. Do so holding only an sxlock, so that clock drivers are free to do
* whatever kind of locking or sleeping they need to.
* On the task thread, invoke the clock_settime() method of the clock. Do so
* holding no locks, so that clock drivers are free to do whatever kind of
* locking or sleeping they need to.
*/
static void
settime_task_func(void *arg, int pending)
@ -126,21 +128,18 @@ settime_task_func(void *arg, int pending)
struct timespec ts;
struct rtc_instance *rtc;
sx_xlock(&rtc_list_lock);
LIST_FOREACH(rtc, &rtc_list, rtc_entries) {
if (!(rtc->flags & CLOCKF_SETTIME_NO_TS)) {
getnanotime(&ts);
if (!(rtc->flags & CLOCKF_SETTIME_NO_ADJ)) {
ts.tv_sec -= utc_offset();
timespecadd(&ts, &rtc->resadj);
}
} else {
ts.tv_sec = 0;
ts.tv_nsec = 0;
rtc = arg;
if (!(rtc->flags & CLOCKF_SETTIME_NO_TS)) {
getnanotime(&ts);
if (!(rtc->flags & CLOCKF_SETTIME_NO_ADJ)) {
ts.tv_sec -= utc_offset();
timespecadd(&ts, &rtc->resadj);
}
CLOCK_SETTIME(rtc->clockdev, &ts);
} else {
ts.tv_sec = 0;
ts.tv_nsec = 0;
}
sx_xunlock(&rtc_list_lock);
CLOCK_SETTIME(rtc->clockdev, &ts);
}
void
@ -152,8 +151,11 @@ clock_register_flags(device_t clockdev, long resolution, int flags)
newrtc->clockdev = clockdev;
newrtc->resolution = (int)resolution;
newrtc->flags = flags;
newrtc->schedns = 0;
newrtc->resadj.tv_sec = newrtc->resolution / 2 / 1000000;
newrtc->resadj.tv_nsec = newrtc->resolution / 2 % 1000000 * 1000;
TIMEOUT_TASK_INIT(taskqueue_thread, &newrtc->stask, 0,
settime_task_func, newrtc);
sx_xlock(&rtc_list_lock);
if (LIST_EMPTY(&rtc_list)) {
@ -192,7 +194,27 @@ clock_unregister(device_t clockdev)
LIST_FOREACH_SAFE(rtc, &rtc_list, rtc_entries, tmp) {
if (rtc->clockdev == clockdev) {
LIST_REMOVE(rtc, rtc_entries);
free(rtc, M_DEVBUF);
break;
}
}
sx_xunlock(&rtc_list_lock);
if (rtc != NULL) {
taskqueue_cancel_timeout(taskqueue_thread, &rtc->stask, NULL);
taskqueue_drain_timeout(taskqueue_thread, &rtc->stask);
free(rtc, M_DEVBUF);
}
}
void
clock_schedule(device_t clockdev, u_int offsetns)
{
struct rtc_instance *rtc;
sx_xlock(&rtc_list_lock);
LIST_FOREACH(rtc, &rtc_list, rtc_entries) {
if (rtc->clockdev == clockdev) {
rtc->schedns = offsetns;
break;
}
}
sx_xunlock(&rtc_list_lock);
@ -275,9 +297,26 @@ inittodr(time_t base)
void
resettodr(void)
{
struct timespec now;
struct rtc_instance *rtc;
sbintime_t sbt;
long waitns;
if (disable_rtc_set)
return;
taskqueue_enqueue(taskqueue_thread, &settime_task);
sx_xlock(&rtc_list_lock);
LIST_FOREACH(rtc, &rtc_list, rtc_entries) {
if (rtc->schedns != 0) {
getnanotime(&now);
waitns = rtc->schedns - now.tv_nsec;
if (waitns < 0)
waitns += 1000000000;
sbt = nstosbt(waitns);
} else
sbt = 0;
taskqueue_enqueue_timeout_sbt(taskqueue_thread,
&rtc->stask, -sbt, 0, C_PREL(31));
}
sx_xunlock(&rtc_list_lock);
}

14
sys/sys/clock.h
View File

@ -77,9 +77,16 @@ int clock_ct_to_ts(struct clocktime *, struct timespec *);
void clock_ts_to_ct(struct timespec *, struct clocktime *);
/*
* Time-of-day clock register/unregister functions, and associated flags. These
* functions can sleep. Upon return from unregister, the clock's methods are
* not running and will not be called again.
* Time-of-day clock functions and flags. These functions might sleep.
*
* clock_register and clock_unregister() do what they say. Upon return from
* unregister, the clock's methods are not running and will not be called again.
*
* clock_schedule() requests that a registered clock's clock_settime() calls
* happen at the given offset into the second. The default is 0, meaning no
* specific scheduling. To schedule the call as soon after top-of-second as
* possible, specify 1. Each clock has its own schedule, but taskqueue_thread
* is shared by many tasks; the timing of the call is not guaranteed.
*
* Flags:
*
@ -102,6 +109,7 @@ void clock_ts_to_ct(struct timespec *, struct clocktime *);
void clock_register(device_t _clockdev, long _resolution_us);
void clock_register_flags(device_t _clockdev, long _resolution_us, int _flags);
void clock_schedule(device_t clockdev, u_int _offsetns);
void clock_unregister(device_t _clockdev);
/*