1 files changed, 67 insertions, 77 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 929846b8b45a..a009c91f7b05 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -164,10 +164,34 @@ static inline struct timespec64 tk_xtime(const struct timekeeper *tk)
 	return ts;
 }
 
+static inline struct timespec64 tk_xtime_coarse(const struct timekeeper *tk)
+{
+	struct timespec64 ts;
+
+	ts.tv_sec = tk->xtime_sec;
+	ts.tv_nsec = tk->coarse_nsec;
+	return ts;
+}
+
+/*
+ * Update the nanoseconds part for the coarse time keepers. They can't rely
+ * on xtime_nsec because xtime_nsec could be adjusted by a small negative
+ * amount when the multiplication factor of the clock is adjusted, which
+ * could cause the coarse clocks to go slightly backwards. See
+ * timekeeping_apply_adjustment(). Thus we keep a separate copy for the coarse
+ * clockids which only is updated when the clock has been set or  we have
+ * accumulated time.
+ */
+static inline void tk_update_coarse_nsecs(struct timekeeper *tk)
+{
+	tk->coarse_nsec = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
+}
+
 static void tk_set_xtime(struct timekeeper *tk, const struct timespec64 *ts)
 {
 	tk->xtime_sec = ts->tv_sec;
 	tk->tkr_mono.xtime_nsec = (u64)ts->tv_nsec << tk->tkr_mono.shift;
+	tk_update_coarse_nsecs(tk);
 }
 
 static void tk_xtime_add(struct timekeeper *tk, const struct timespec64 *ts)
@@ -175,6 +199,7 @@ static void tk_xtime_add(struct timekeeper *tk, const struct timespec64 *ts)
 	tk->xtime_sec += ts->tv_sec;
 	tk->tkr_mono.xtime_nsec += (u64)ts->tv_nsec << tk->tkr_mono.shift;
 	tk_normalize_xtime(tk);
+	tk_update_coarse_nsecs(tk);
 }
 
 static void tk_set_wall_to_mono(struct timekeeper *tk, struct timespec64 wtm)
@@ -682,19 +707,20 @@ static void timekeeping_update_from_shadow(struct tk_data *tkd, unsigned int act
 }
 
 /**
- * timekeeping_forward - update clock to given cycle now value
+ * timekeeping_forward_now - update clock to the current time
  * @tk:		Pointer to the timekeeper to update
- * @cycle_now:  Current clocksource read value
  *
  * Forward the current clock to update its state since the last call to
  * update_wall_time(). This is useful before significant clock changes,
  * as it avoids having to deal with this time offset explicitly.
  */
-static void timekeeping_forward(struct timekeeper *tk, u64 cycle_now)
+static void timekeeping_forward_now(struct timekeeper *tk)
 {
-	u64 delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask,
-				      tk->tkr_mono.clock->max_raw_delta);
+	u64 cycle_now, delta;
 
+	cycle_now = tk_clock_read(&tk->tkr_mono);
+	delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask,
+				  tk->tkr_mono.clock->max_raw_delta);
 	tk->tkr_mono.cycle_last = cycle_now;
 	tk->tkr_raw.cycle_last  = cycle_now;
 
@@ -707,21 +733,7 @@ static void timekeeping_forward(struct timekeeper *tk, u64 cycle_now)
 		tk_normalize_xtime(tk);
 		delta -= incr;
 	}
-}
-
-/**
- * timekeeping_forward_now - update clock to the current time
- * @tk:		Pointer to the timekeeper to update
- *
- * Forward the current clock to update its state since the last call to
- * update_wall_time(). This is useful before significant clock changes,
- * as it avoids having to deal with this time offset explicitly.
- */
-static void timekeeping_forward_now(struct timekeeper *tk)
-{
-	u64 cycle_now = tk_clock_read(&tk->tkr_mono);
-
-	timekeeping_forward(tk, cycle_now);
+	tk_update_coarse_nsecs(tk);
 }
 
 /**
@@ -818,8 +830,8 @@ EXPORT_SYMBOL_GPL(ktime_get_with_offset);
 ktime_t ktime_get_coarse_with_offset(enum tk_offsets offs)
 {
 	struct timekeeper *tk = &tk_core.timekeeper;
-	unsigned int seq;
 	ktime_t base, *offset = offsets[offs];
+	unsigned int seq;
 	u64 nsecs;
 
 	WARN_ON(timekeeping_suspended);
@@ -827,7 +839,7 @@ ktime_t ktime_get_coarse_with_offset(enum tk_offsets offs)
 	do {
 		seq = read_seqcount_begin(&tk_core.seq);
 		base = ktime_add(tk->tkr_mono.base, *offset);
-		nsecs = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
+		nsecs = tk->coarse_nsec;
 
 	} while (read_seqcount_retry(&tk_core.seq, seq));
 
@@ -2165,54 +2177,6 @@ static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset,
 	return offset;
 }
 
-static u64 timekeeping_accumulate(struct timekeeper *tk, u64 offset,
-				  enum timekeeping_adv_mode mode,
-				  unsigned int *clock_set)
-{
-	int shift = 0, maxshift;
-
-	/*
-	 * TK_ADV_FREQ indicates that adjtimex(2) directly set the
-	 * frequency or the tick length.
-	 *
-	 * Accumulate the offset, so that the new multiplier starts from
-	 * now. This is required as otherwise for offsets, which are
-	 * smaller than tk::cycle_interval, timekeeping_adjust() could set
-	 * xtime_nsec backwards, which subsequently causes time going
-	 * backwards in the coarse time getters. But even for the case
-	 * where offset is greater than tk::cycle_interval the periodic
-	 * accumulation does not have much value.
-	 *
-	 * Also reset tk::ntp_error as it does not make sense to keep the
-	 * old accumulated error around in this case.
-	 */
-	if (mode == TK_ADV_FREQ) {
-		timekeeping_forward(tk, tk->tkr_mono.cycle_last + offset);
-		tk->ntp_error = 0;
-		return 0;
-	}
-
-	/*
-	 * With NO_HZ we may have to accumulate many cycle_intervals
-	 * (think "ticks") worth of time at once. To do this efficiently,
-	 * we calculate the largest doubling multiple of cycle_intervals
-	 * that is smaller than the offset.  We then accumulate that
-	 * chunk in one go, and then try to consume the next smaller
-	 * doubled multiple.
-	 */
-	shift = ilog2(offset) - ilog2(tk->cycle_interval);
-	shift = max(0, shift);
-	/* Bound shift to one less than what overflows tick_length */
-	maxshift = (64 - (ilog2(ntp_tick_length()) + 1)) - 1;
-	shift = min(shift, maxshift);
-	while (offset >= tk->cycle_interval) {
-		offset = logarithmic_accumulation(tk, offset, shift, clock_set);
-		if (offset < tk->cycle_interval << shift)
-			shift--;
-	}
-	return offset;
-}
-
 /*
  * timekeeping_advance - Updates the timekeeper to the current time and
  * current NTP tick length
@@ -2222,7 +2186,8 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode)
 	struct timekeeper *tk = &tk_core.shadow_timekeeper;
 	struct timekeeper *real_tk = &tk_core.timekeeper;
 	unsigned int clock_set = 0;
-	u64 offset;
+	int shift = 0, maxshift;
+	u64 offset, orig_offset;
 
 	guard(raw_spinlock_irqsave)(&tk_core.lock);
 
@@ -2233,12 +2198,29 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode)
 	offset = clocksource_delta(tk_clock_read(&tk->tkr_mono),
 				   tk->tkr_mono.cycle_last, tk->tkr_mono.mask,
 				   tk->tkr_mono.clock->max_raw_delta);
-
+	orig_offset = offset;
 	/* Check if there's really nothing to do */
 	if (offset < real_tk->cycle_interval && mode == TK_ADV_TICK)
 		return false;
 
-	offset = timekeeping_accumulate(tk, offset, mode, &clock_set);
+	/*
+	 * With NO_HZ we may have to accumulate many cycle_intervals
+	 * (think "ticks") worth of time at once. To do this efficiently,
+	 * we calculate the largest doubling multiple of cycle_intervals
+	 * that is smaller than the offset.  We then accumulate that
+	 * chunk in one go, and then try to consume the next smaller
+	 * doubled multiple.
+	 */
+	shift = ilog2(offset) - ilog2(tk->cycle_interval);
+	shift = max(0, shift);
+	/* Bound shift to one less than what overflows tick_length */
+	maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1;
+	shift = min(shift, maxshift);
+	while (offset >= tk->cycle_interval) {
+		offset = logarithmic_accumulation(tk, offset, shift, &clock_set);
+		if (offset < tk->cycle_interval<<shift)
+			shift--;
+	}
 
 	/* Adjust the multiplier to correct NTP error */
 	timekeeping_adjust(tk, offset);
@@ -2249,6 +2231,14 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode)
 	 */
 	clock_set |= accumulate_nsecs_to_secs(tk);
 
+	/*
+	 * To avoid inconsistencies caused adjtimex TK_ADV_FREQ calls
+	 * making small negative adjustments to the base xtime_nsec
+	 * value, only update the coarse clocks if we accumulated time
+	 */
+	if (orig_offset != offset)
+		tk_update_coarse_nsecs(tk);
+
 	timekeeping_update_from_shadow(&tk_core, clock_set);
 
 	return !!clock_set;
@@ -2292,7 +2282,7 @@ void ktime_get_coarse_real_ts64(struct timespec64 *ts)
 	do {
 		seq = read_seqcount_begin(&tk_core.seq);
 
-		*ts = tk_xtime(tk);
+		*ts = tk_xtime_coarse(tk);
 	} while (read_seqcount_retry(&tk_core.seq, seq));
 }
 EXPORT_SYMBOL(ktime_get_coarse_real_ts64);
@@ -2315,7 +2305,7 @@ void ktime_get_coarse_real_ts64_mg(struct timespec64 *ts)
 
 	do {
 		seq = read_seqcount_begin(&tk_core.seq);
-		*ts = tk_xtime(tk);
+		*ts = tk_xtime_coarse(tk);
 		offset = tk_core.timekeeper.offs_real;
 	} while (read_seqcount_retry(&tk_core.seq, seq));
 
@@ -2394,12 +2384,12 @@ void ktime_get_coarse_ts64(struct timespec64 *ts)
 	do {
 		seq = read_seqcount_begin(&tk_core.seq);
 
-		now = tk_xtime(tk);
+		now = tk_xtime_coarse(tk);
 		mono = tk->wall_to_monotonic;
 	} while (read_seqcount_retry(&tk_core.seq, seq));
 
 	set_normalized_timespec64(ts, now.tv_sec + mono.tv_sec,
-				now.tv_nsec + mono.tv_nsec);
+				  now.tv_nsec + mono.tv_nsec);
 }
 EXPORT_SYMBOL(ktime_get_coarse_ts64);