time/timekeeping: Avoid invoking clock_was_set() twice

do_adjtimex() might end up scheduling a delayed clock_was_set() via
timekeeping_advance() and then invoke clock_was_set() directly which is
pointless.

Make timekeeping_advance() return whether an invocation of clock_was_set()
is required and handle it at the call sites which allows do_adjtimex() to
issue a single direct call if required.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.580966888@linutronix.de

kernel/time/timekeeping.c

@@ -2127,7 +2127,7 @@ static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset,
  * timekeeping_advance - Updates the timekeeper to the current time and
  * current NTP tick length
  */
-static void timekeeping_advance(enum timekeeping_adv_mode mode)
+static bool timekeeping_advance(enum timekeeping_adv_mode mode)
 {
 	struct timekeeper *real_tk = &tk_core.timekeeper;
 	struct timekeeper *tk = &shadow_timekeeper;
@@ -2198,9 +2198,8 @@ static void timekeeping_advance(enum timekeeping_adv_mode mode)
 	write_seqcount_end(&tk_core.seq);
 out:
 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
-	if (clock_set)
-		/* Have to call _delayed version, since in irq context*/
-		clock_was_set_delayed();
+
+	return !!clock_set;
 }
 
 /**
@@ -2209,7 +2208,8 @@ static void timekeeping_advance(enum timekeeping_adv_mode mode)
  */
 void update_wall_time(void)
 {
-	timekeeping_advance(TK_ADV_TICK);
+	if (timekeeping_advance(TK_ADV_TICK))
+		clock_was_set_delayed();
 }
 
 /**
@@ -2389,8 +2389,9 @@ int do_adjtimex(struct __kernel_timex *txc)
 {
 	struct timekeeper *tk = &tk_core.timekeeper;
 	struct audit_ntp_data ad;
-	unsigned long flags;
+	bool clock_set = false;
 	struct timespec64 ts;
+	unsigned long flags;
 	s32 orig_tai, tai;
 	int ret;
 
@@ -2425,6 +2426,7 @@ int do_adjtimex(struct __kernel_timex *txc)
 	if (tai != orig_tai) {
 		__timekeeping_set_tai_offset(tk, tai);
 		timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
+		clock_set = true;
 	}
 	tk_update_leap_state(tk);
 
@@ -2435,9 +2437,9 @@ int do_adjtimex(struct __kernel_timex *txc)
 
 	/* Update the multiplier immediately if frequency was set directly */
 	if (txc->modes & (ADJ_FREQUENCY | ADJ_TICK))
-		timekeeping_advance(TK_ADV_FREQ);
+		clock_set |= timekeeping_advance(TK_ADV_FREQ);
 
-	if (tai != orig_tai)
+	if (clock_set)
 		clock_was_set();
 
 	ntp_notify_cmos_timer();