linux-kernel - [PATCH v11 17/20] timers: Introduce function to check timer base is

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Message-Id: <20240221090548.36600-18-anna-maria@linutronix.de>
Date: Wed, 21 Feb 2024 10:05:45 +0100
From: Anna-Maria Behnsen <anna-maria@...utronix.de>
To: linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
	John Stultz <jstultz@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Eric Dumazet <edumazet@...gle.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Arjan van de Ven <arjan@...radead.org>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Rik van Riel <riel@...riel.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sebastian Siewior <bigeasy@...utronix.de>,
	Giovanni Gherdovich <ggherdovich@...e.cz>,
	Lukasz Luba <lukasz.luba@....com>,
	"Gautham R . Shenoy" <gautham.shenoy@....com>,
	Srinivas Pandruvada <srinivas.pandruvada@...el.com>,
	K Prateek Nayak <kprateek.nayak@....com>,
	Christian Loehle <christian.loehle@....com>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: [PATCH v11 17/20] timers: Introduce function to check timer base is_idle flag

To prepare for the conversion of the NOHZ timer placement to a pull at
expiry time model it's required to have a function that returns the value
of the is_idle flag of the timer base to keep the hierarchy states during
online in sync with timer base state.

No functional change.

Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
---
v10: Fix fallout of 0day: Move function definition of timer_base_is_idle()
     into SMP && NO_HZ_COMMON ifdef section

v9: new in v9
---
 kernel/time/tick-internal.h |  1 +
 kernel/time/timer.c         | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index ccf39befde85..7e3090109e33 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -165,6 +165,7 @@ extern void fetch_next_timer_interrupt_remote(unsigned long basej, u64 basem,
 					      unsigned int cpu);
 extern void timer_lock_remote_bases(unsigned int cpu);
 extern void timer_unlock_remote_bases(unsigned int cpu);
+extern bool timer_base_is_idle(void);
 # endif
 #else /* CONFIG_NO_HZ_COMMON */
 static inline void timers_update_nohz(void) { }
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 7b9f9ed25fc2..3f618ee39763 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -2114,6 +2114,16 @@ void timer_lock_remote_bases(unsigned int cpu)
 	raw_spin_lock(&base_local->lock);
 	raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING);
 }
+
+/**
+ * timer_base_is_idle() - Return whether timer base is set idle
+ *
+ * Returns value of local timer base is_idle value.
+ */
+bool timer_base_is_idle(void)
+{
+	return __this_cpu_read(timer_bases[BASE_LOCAL].is_idle);
+}
 # endif /* CONFIG_SMP */
 
 static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem,
-- 
2.39.2