[PATCH] Fix POSIX timers to give CLOCK_MONOTONIC full

The POSIX CLOCK_MONOTONIC currently has only 1/HZ resolution.  Further, it is
tied to jiffies (i.e.  is a restatment of jiffies) rather than "xtime" or the
gettimeofday() clock.

This patch changes CLOCK_MONOTONIC to be a restatment of gettimeofday() plus
an offset to remove any clock setting activity from CLOCK_MONOTONIC.  An
offset is kept that represents the difference between CLOCK_MONOTONIC and
gettimeofday().  This offset is updated when ever the gettimeofday() clock is
set to back the clock setting change out of CLOCK_MONOTONIC (which by the
standard, can not be set).

With this change CLOCK_REALTIME (a direct restatement of gettimeofday()),
CLOCK_MONOTONIC and gettimeofday() will all tick at the same time and with
the same rate.  And all will be affected by NTP adjustments (save those which
actually set the time).

arch/i386/kernel/time.c

@@ -124,15 +124,28 @@ void do_settimeofday(struct timeval *tv)
 	 * made, and then undo it!
 	 */
 	tv->tv_usec -= timer->get_offset();
-	tv->tv_usec -= (jiffies - wall_jiffies) * (1000000 / HZ);
+	tv->tv_usec -= (jiffies - wall_jiffies) * (USEC_PER_SEC / HZ);
 
 	while (tv->tv_usec < 0) {
-		tv->tv_usec += 1000000;
+		tv->tv_usec += USEC_PER_SEC;
 		tv->tv_sec--;
 	}
+	tv->tv_usec *= NSEC_PER_USEC;
+
+	wall_to_monotonic.tv_sec += xtime.tv_sec - tv->tv_sec;
+	wall_to_monotonic.tv_nsec += xtime.tv_nsec - tv->tv_usec;
+
+	if (wall_to_monotonic.tv_nsec > NSEC_PER_SEC) {
+		wall_to_monotonic.tv_nsec -= NSEC_PER_SEC;
+		wall_to_monotonic.tv_sec++;
+	}
+	if (wall_to_monotonic.tv_nsec < 0) {
+		wall_to_monotonic.tv_nsec += NSEC_PER_SEC;
+		wall_to_monotonic.tv_sec--;
+	}
 
 	xtime.tv_sec = tv->tv_sec;
-	xtime.tv_nsec = (tv->tv_usec * 1000);
+	xtime.tv_nsec = tv->tv_usec;
 	time_adjust = 0;		/* stop active adjtime() */
 	time_status |= STA_UNSYNC;
 	time_maxerror = NTP_PHASE_LIMIT;
@@ -322,7 +335,9 @@ void __init time_init(void)
 {
 	
 	xtime.tv_sec = get_cmos_time();
-	xtime.tv_nsec = 0;
+	wall_to_monotonic.tv_sec = -xtime.tv_sec + INITIAL_JIFFIES / HZ;
+	xtime.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
+	wall_to_monotonic.tv_nsec = 0;
 
 
 	timer = select_timer();

include/linux/time.h

@@ -140,6 +140,7 @@ mktime (unsigned int year, unsigned int mon,
 }
 
 extern struct timespec xtime;
+extern struct timespec wall_to_monotonic;
 extern seqlock_t xtime_lock;
 
 static inline unsigned long get_seconds(void)
@@ -200,6 +201,9 @@ struct	itimerval {
 #define CLOCK_MONOTONIC_HR	  5
 
 #define MAX_CLOCKS 6
+#define CLOCKS_MASK  (CLOCK_REALTIME | CLOCK_MONOTONIC | \
+                     CLOCK_REALTIME_HR | CLOCK_MONOTONIC_HR)
+#define CLOCKS_MONO (CLOCK_MONOTONIC & CLOCK_MONOTONIC_HR)
 
 /*
  * The various flags for setting POSIX.1b interval timers.

kernel/posix-timers.c

@@ -48,7 +48,7 @@
  * The idr_get_new *may* call slab for more memory so it must not be
  * called under a spin lock.  Likewise idr_remore may release memory
  * (but it may be ok to do this under a lock...).
- * idr_find is just a memory look up and is quite fast.  A zero return
+ * idr_find is just a memory look up and is quite fast.  A -1 return
  * indicates that the requested id does not exist.
  */
 
@@ -82,6 +82,7 @@ static spinlock_t idr_lock = SPIN_LOCK_UNLOCKED;
  * For some reason mips/mips64 define the SIGEV constants plus 128.
  * Here we define a mask to get rid of the common bits.	 The
  * optimizer should make this costless to all but mips.
+ * Note that no common bits (the non-mips case) will give 0xffffffff.
  */
 #define MIPS_SIGEV ~(SIGEV_NONE & \
 		      SIGEV_SIGNAL & \
@@ -93,7 +94,7 @@ static spinlock_t idr_lock = SPIN_LOCK_UNLOCKED;
  * The timer ID is turned into a timer address by idr_find().
  * Verifying a valid ID consists of:
  *
- * a) checking that idr_find() returns other than zero.
+ * a) checking that idr_find() returns other than -1.
  * b) checking that the timer id matches the one in the timer itself.
  * c) that the timer owner is in the callers thread group.
  */
@@ -162,6 +163,8 @@ static struct k_clock posix_clocks[MAX_CLOCKS];
 
 void register_posix_clock(int clock_id, struct k_clock *new_clock);
 static int do_posix_gettime(struct k_clock *clock, struct timespec *tp);
+static u64 do_posix_clock_monotonic_gettime_parts(
+	struct timespec *tp, struct timespec *mo);
 int do_posix_clock_monotonic_gettime(struct timespec *tp);
 int do_posix_clock_monotonic_settime(struct timespec *tp);
 static struct k_itimer *lock_timer(timer_t timer_id, unsigned long *flags);
@@ -192,7 +195,7 @@ __initcall(init_posix_timers);
 
 static void tstojiffie(struct timespec *tp, int res, u64 *jiff)
 {
-	unsigned long sec = tp->tv_sec;
+	long sec = tp->tv_sec;
 	long nsec = tp->tv_nsec + res - 1;
 
 	if (nsec > NSEC_PER_SEC) {
@@ -210,7 +213,7 @@ static void tstojiffie(struct timespec *tp, int res, u64 *jiff)
 	 * below.  Here it is enough to just discard the high order
 	 * bits.
 	 */
-	*jiff = (u64)sec * HZ;
+	*jiff = (s64)sec * HZ;
 	/*
 	 * Do the res thing. (Don't forget the add in the declaration of nsec)
 	 */
@@ -221,17 +224,6 @@ static void tstojiffie(struct timespec *tp, int res, u64 *jiff)
 	*jiff += nsec / (NSEC_PER_SEC / HZ);
 }
 
-static void tstotimer(struct itimerspec *time, struct k_itimer *timer)
-{
-	u64 result;
-	int res = posix_clocks[timer->it_clock].res;
-
-	tstojiffie(&time->it_value, res, &result);
-	timer->it_timer.expires = (unsigned long)result;
-	tstojiffie(&time->it_interval, res, &result);
-	timer->it_incr = (unsigned long)result;
-}
-
 static void schedule_next_timer(struct k_itimer *timr)
 {
 	struct now_struct now;
@@ -690,57 +682,81 @@ sys_timer_getoverrun(timer_t timer_id)
  * If it is relative time, we need to add the current (CLOCK_MONOTONIC)
  * time to it to get the proper time for the timer.
  */
-static int adjust_abs_time(struct k_clock *clock, struct timespec *tp, int abs)
+static int adjust_abs_time(struct k_clock *clock, struct timespec *tp, 
+			   int abs, u64 *exp)
 {
 	struct timespec now;
-	struct timespec oc;
-	do_posix_clock_monotonic_gettime(&now);
-
-	if (!abs || (posix_clocks[CLOCK_MONOTONIC].clock_get !=
-							clock->clock_get)) {
-		if (abs)
-			do_posix_gettime(clock, &oc);
-		else
-			oc.tv_nsec = oc.tv_sec = 0;
-
-		tp->tv_sec += now.tv_sec - oc.tv_sec;
-		tp->tv_nsec += now.tv_nsec - oc.tv_nsec;
+	struct timespec oc = *tp;
+	struct timespec wall_to_mono;
+	u64 jiffies_64_f;
+	int rtn =0;
 
+	if (abs) {
+		/*
+		 * The mask pick up the 4 basic clocks 
+		 */
+		if (!(clock - &posix_clocks[0]) & ~CLOCKS_MASK) {
+			jiffies_64_f = do_posix_clock_monotonic_gettime_parts(
+				&now,  &wall_to_mono);
+			/*
+			 * If we are doing a MONOTONIC clock
+			 */
+			if((clock - &posix_clocks[0]) & CLOCKS_MONO){
+				now.tv_sec += wall_to_mono.tv_sec;
+				now.tv_nsec += wall_to_mono.tv_nsec;
+			}
+		} else {
+			/*
+			 * Not one of the basic clocks
+			 */
+			do_posix_gettime(clock, &now);	
+			jiffies_64_f = get_jiffies_64();
+		}
+		/*
+		 * Take away now to get delta
+		 */
+		oc.tv_sec -= now.tv_sec;
+		oc.tv_nsec -= now.tv_nsec;
 		/*
 		 * Normalize...
 		 */
-		if ((tp->tv_nsec - NSEC_PER_SEC) >= 0) {
-			tp->tv_nsec -= NSEC_PER_SEC;
-			tp->tv_sec++;
+		while ((oc.tv_nsec - NSEC_PER_SEC) >= 0) {
+			oc.tv_nsec -= NSEC_PER_SEC;
+			oc.tv_sec++;
 		}
-		if ((tp->tv_nsec) < 0) {
-			tp->tv_nsec += NSEC_PER_SEC;
-			tp->tv_sec--;
+		while ((oc.tv_nsec) < 0) {
+			oc.tv_nsec += NSEC_PER_SEC;
+			oc.tv_sec--;
 		}
+	}else{
+		jiffies_64_f = get_jiffies_64();
 	}
 	/*
-	 * Check if the requested time is prior to now (if so set now) or
-	 * is more than the timer code can handle (if so we error out).
-	 * The (unsigned) catches the case of prior to "now" with the same
-	 * test.  Only on failure do we sort out what happened, and then
-	 * we use the (unsigned) to error out negative seconds.
+	 * Check if the requested time is prior to now (if so set now)
 	 */
-	if ((unsigned) (tp->tv_sec - now.tv_sec) > (MAX_JIFFY_OFFSET / HZ)) {
-		if ((unsigned) tp->tv_sec < now.tv_sec) {
-			tp->tv_sec = now.tv_sec;
-			tp->tv_nsec = now.tv_nsec;
-		} else
+	if (oc.tv_sec < 0)
+		oc.tv_sec = oc.tv_nsec = 0;
+	tstojiffie(&oc, clock->res, exp);
+
+	/*
+	 * Check if the requested time is more than the timer code
+	 * can handle (if so we error out but return the value too).
+	 */
+	if (*exp > ((u64)MAX_JIFFY_OFFSET))
 			/*
 			 * This is a considered response, not exactly in
 			 * line with the standard (in fact it is silent on
-			 * possible overflows).  We assume such a large
+			 * possible overflows).  We assume such a large 
 			 * value is ALMOST always a programming error and
 			 * try not to compound it by setting a really dumb
 			 * value.
 			 */
-			return -EINVAL;
-	}
-	return 0;
+			rtn = -EINVAL;
+	/*
+	 * return the actual jiffies expire time, full 64 bits
+	 */
+	*exp += jiffies_64_f;
+	return rtn;
 }
 
 /* Set a POSIX.1b interval timer. */
@@ -750,6 +766,7 @@ do_timer_settime(struct k_itimer *timr, int flags,
 		 struct itimerspec *new_setting, struct itimerspec *old_setting)
 {
 	struct k_clock *clock = &posix_clocks[timr->it_clock];
+	u64 expire_64;
 
 	if (old_setting)
 		do_timer_gettime(timr, old_setting);
@@ -788,14 +805,15 @@ do_timer_settime(struct k_itimer *timr, int flags,
 		return 0;
 	}
 
-	if ((flags & TIMER_ABSTIME) &&
-	    (clock->clock_get != do_posix_clock_monotonic_gettime))
-		// FIXME: what is this?
-		;
 	if (adjust_abs_time(clock,
-			    &new_setting->it_value, flags & TIMER_ABSTIME))
+			    &new_setting->it_value, flags & TIMER_ABSTIME, 
+			    &expire_64)) {
 		return -EINVAL;
-	tstotimer(new_setting, timr);
+	}
+	timr->it_timer.expires = (unsigned long)expire_64;	
+	tstojiffie(&new_setting->it_interval, clock->res, &expire_64);
+	timr->it_incr = (unsigned long)expire_64;
+
 
 	/*
 	 * For some reason the timer does not fire immediately if expires is
@@ -964,30 +982,46 @@ static int do_posix_gettime(struct k_clock *clock, struct timespec *tp)
  * Note also that the while loop assures that the sub_jiff_offset
  * will be less than a jiffie, thus no need to normalize the result.
  * Well, not really, if called with ints off :(
- *
- * HELP, this code should make an attempt at resolution beyond the
- * jiffie.  Trouble is this is "arch" dependent...
  */
 
-int do_posix_clock_monotonic_gettime(struct timespec *tp)
+static u64 do_posix_clock_monotonic_gettime_parts(
+	struct timespec *tp, struct timespec *mo)
 {
-	long sub_sec;
-	u64 jiffies_64_f;
-
-#if (BITS_PER_LONG > 32)
-	jiffies_64_f = jiffies_64;
-#else
+	u64 jiff;
+	struct timeval tpv;
 	unsigned int seq;
 
 	do {
 		seq = read_seqbegin(&xtime_lock);
-		jiffies_64_f = jiffies_64;
+		do_gettimeofday(&tpv);
+		*mo = wall_to_monotonic;
+		jiff = jiffies_64;
 
-	} while (read_seqretry(&xtime_lock, seq));
-#endif
-	tp->tv_sec = div_long_long_rem(jiffies_64_f, HZ, &sub_sec);
-	tp->tv_nsec = sub_sec * (NSEC_PER_SEC / HZ);
+	} while(read_seqretry(&xtime_lock, seq));
 
+	/*
+	 * Love to get this before it is converted to usec.
+	 * It would save a div AND a mpy.
+	 */
+	tp->tv_sec = tpv.tv_sec;
+	tp->tv_nsec = tpv.tv_usec * NSEC_PER_USEC;
+
+	return jiff;
+}
+
+int do_posix_clock_monotonic_gettime(struct timespec *tp)
+{
+	struct timespec wall_to_mono;
+
+	do_posix_clock_monotonic_gettime_parts(tp, &wall_to_mono);
+
+	tp->tv_sec += wall_to_mono.tv_sec;
+	tp->tv_nsec += wall_to_mono.tv_nsec;
+
+	if ((tp->tv_nsec - NSEC_PER_SEC) > 0) {
+		tp->tv_nsec -= NSEC_PER_SEC;
+		tp->tv_sec++;
+	}
 	return 0;
 }
 
@@ -1138,7 +1172,7 @@ do_clock_nanosleep(clockid_t which_clock, int flags, struct timespec *tsave)
 	struct timespec t;
 	struct timer_list new_timer;
 	DECLARE_WAITQUEUE(abs_wqueue, current);
-	u64 rq_time = 0;
+	u64 rq_time = (u64)0;
 	s64 left;
 	int abs;
 	struct restart_block *restart_block =
@@ -1163,7 +1197,7 @@ do_clock_nanosleep(clockid_t which_clock, int flags, struct timespec *tsave)
 		if (!rq_time)
 			return -EINTR;
 		left = rq_time - get_jiffies_64();
-		if (left <= 0LL)
+		if (left <= (s64)0)
 			return 0;	/* Already passed */
 	}
 
@@ -1174,14 +1208,14 @@ do_clock_nanosleep(clockid_t which_clock, int flags, struct timespec *tsave)
 	do {
 		t = *tsave;
 		if (abs || !rq_time) {
-			adjust_abs_time(&posix_clocks[which_clock], &t, abs);
-			tstojiffie(&t, posix_clocks[which_clock].res, &rq_time);
+			adjust_abs_time(&posix_clocks[which_clock], &t, abs,
+					&rq_time);
 		}
 
 		left = rq_time - get_jiffies_64();
-		if (left >= MAX_JIFFY_OFFSET)
-			left = MAX_JIFFY_OFFSET;
-		if (left < 0)
+		if (left >= (s64)MAX_JIFFY_OFFSET)
+			left = (s64)MAX_JIFFY_OFFSET;
+		if (left < (s64)0)
 			break;
 
 		new_timer.expires = jiffies + left;
@@ -1192,12 +1226,12 @@ do_clock_nanosleep(clockid_t which_clock, int flags, struct timespec *tsave)
 
 		del_timer_sync(&new_timer);
 		left = rq_time - get_jiffies_64();
-	} while (left > 0 && !test_thread_flag(TIF_SIGPENDING));
+	} while (left > (s64)0 && !test_thread_flag(TIF_SIGPENDING));
 
 	if (abs_wqueue.task_list.next)
 		finish_wait(&nanosleep_abs_wqueue, &abs_wqueue);
 
-	if (left > 0) {
+	if (left > (s64)0) {
 		unsigned long rmd;
 
 		/*

kernel/timer.c

@@ -441,8 +441,16 @@ static inline void __run_timers(tvec_base_t *base)
 unsigned long tick_usec = TICK_USEC; 		/* ACTHZ   period (usec) */
 unsigned long tick_nsec = TICK_NSEC(TICK_USEC);	/* USER_HZ period (nsec) */
 
-/* The current time */
+/* 
+ * The current time 
+ * wall_to_monotonic is what we need to add to xtime (or xtime corrected 
+ * for sub jiffie times) to get to monotonic time.  Monotonic is pegged at zero
+ * at zero at system boot time, so wall_to_monotonic will be negative,
+ * however, we will ALWAYS keep the tv_nsec part positive so we can use
+ * the usual normalization.
+ */
 struct timespec xtime __attribute__ ((aligned (16)));
+struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
 
 /* Don't completely fail for HZ > 500.  */
 int tickadj = 500/HZ ? : 1;		/* microsecs */
@@ -508,6 +516,7 @@ static void second_overflow(void)
     case TIME_INS:
 	if (xtime.tv_sec % 86400 == 0) {
 	    xtime.tv_sec--;
+	    wall_to_monotonic.tv_sec++;
 	    time_state = TIME_OOP;
 	    clock_was_set();
 	    printk(KERN_NOTICE "Clock: inserting leap second 23:59:60 UTC\n");
@@ -517,6 +526,7 @@ static void second_overflow(void)
     case TIME_DEL:
 	if ((xtime.tv_sec + 1) % 86400 == 0) {
 	    xtime.tv_sec++;
+	    wall_to_monotonic.tv_sec--;
 	    time_state = TIME_WAIT;
 	    clock_was_set();
 	    printk(KERN_NOTICE "Clock: deleting leap second 23:59:59 UTC\n");