[tip: timers/core] tick/sched: Split out jiffies update helper function

[tip-bot2 for Richard Cochran (linutronix GmbH)]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     4c532939aa2e9345ee346bc69d3d12d56d5aa9aa
Gitweb:        https://git.kernel.org/tip/4c532939aa2e9345ee346bc69d3d12d56d5aa9aa
Author:        Richard Cochran (linutronix GmbH) <richardcochran@xxxxxxxxx>
AuthorDate:    Wed, 21 Feb 2024 10:05:44 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Thu, 22 Feb 2024 17:52:32 +01:00

tick/sched: Split out jiffies update helper function

The logic to get the time of the last jiffies update will be needed by
the timer pull model as well.

Move the code into a global function in anticipation of the new caller.

No functional change.

Signed-off-by: Richard Cochran (linutronix GmbH) <richardcochran@xxxxxxxxx>
Signed-off-by: Anna-Maria Behnsen <anna-maria@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240221090548.36600-17-anna-maria@xxxxxxxxxxxxx

---
 kernel/time/tick-internal.h |  1 +
 kernel/time/tick-sched.c    | 26 +++++++++++++++++++-------
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 8b0c28e..ccf39be 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -157,6 +157,7 @@ static inline void tick_nohz_init(void) { }
 #ifdef CONFIG_NO_HZ_COMMON
 extern unsigned long tick_nohz_active;
 extern void timers_update_nohz(void);
+extern u64 get_jiffies_update(unsigned long *basej);
 # ifdef CONFIG_SMP
 extern struct static_key_false timers_migration_enabled;
 extern void fetch_next_timer_interrupt_remote(unsigned long basej, u64 basem,
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f6b6133..417bb7f 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -799,6 +799,24 @@ static inline bool local_timer_softirq_pending(void)
 	return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
 }
 
+/*
+ * Read jiffies and the time when jiffies were updated last
+ */
+u64 get_jiffies_update(unsigned long *basej)
+{
+	unsigned long basejiff;
+	unsigned int seq;
+	u64 basemono;
+
+	do {
+		seq = read_seqcount_begin(&jiffies_seq);
+		basemono = last_jiffies_update;
+		basejiff = jiffies;
+	} while (read_seqcount_retry(&jiffies_seq, seq));
+	*basej = basejiff;
+	return basemono;
+}
+
 /**
  * tick_nohz_next_event() - return the clock monotonic based next event
  * @ts:		pointer to tick_sched struct
@@ -813,14 +831,8 @@ static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
 {
 	u64 basemono, next_tick, delta, expires;
 	unsigned long basejiff;
-	unsigned int seq;
 
-	/* Read jiffies and the time when jiffies were updated last */
-	do {
-		seq = read_seqcount_begin(&jiffies_seq);
-		basemono = last_jiffies_update;
-		basejiff = jiffies;
-	} while (read_seqcount_retry(&jiffies_seq, seq));
+	basemono = get_jiffies_update(&basejiff);
 	ts->last_jiffies = basejiff;
 	ts->timer_expires_base = basemono;