linux-kernel - [PATCH v9 05/32] tracing/timers: Add tracepoint for tracking timer base is

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Date:   Fri,  1 Dec 2023 10:26:27 +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>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: [PATCH v9 05/32] tracing/timers: Add tracepoint for tracking timer base is_idle flag

When debugging timer code the timer tracepoints are very important. There
is no tracepoint when the is_idle flag of the timer base changes. Instead
of always adding manually trace_printk(), add tracepoints which can be
easily enabled whenever required.

Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
---
v9: New in v9
---
 include/trace/events/timer.h | 20 ++++++++++++++++++++
 kernel/time/timer.c          |  2 ++
 2 files changed, 22 insertions(+)

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index 99ada928d445..1ef58a04fc57 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -142,6 +142,26 @@ DEFINE_EVENT(timer_class, timer_cancel,
 	TP_ARGS(timer)
 );
 
+TRACE_EVENT(timer_base_idle,
+
+	TP_PROTO(bool is_idle, unsigned int cpu),
+
+	TP_ARGS(is_idle, cpu),
+
+	TP_STRUCT__entry(
+		__field( bool,		is_idle	)
+		__field( unsigned int,	cpu	)
+	),
+
+	TP_fast_assign(
+		__entry->is_idle	= is_idle;
+		__entry->cpu		= cpu;
+	),
+
+	TP_printk("is_idle=%d cpu=%d",
+		  __entry->is_idle, __entry->cpu)
+);
+
 #define decode_clockid(type)						\
 	__print_symbolic(type,						\
 		{ CLOCK_REALTIME,	"CLOCK_REALTIME"	},	\
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index a81d793a43d0..46a9b96a3976 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1964,6 +1964,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
 		if ((expires - basem) > TICK_NSEC)
 			base->is_idle = true;
 	}
+	trace_timer_base_idle(base->is_idle, base->cpu);
 	raw_spin_unlock(&base->lock);
 
 	return cmp_next_hrtimer_event(basem, expires);
@@ -1985,6 +1986,7 @@ void timer_clear_idle(void)
 	 * the lock in the exit from idle path.
 	 */
 	base->is_idle = false;
+	trace_timer_base_idle(0, smp_processor_id());
 }
 #endif
 
-- 
2.39.2