Commit b573c731 authored by Anna-Maria Behnsen's avatar Anna-Maria Behnsen Committed by Thomas Gleixner
Browse files

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: default avatarAnna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20231201092654.34614-6-anna-maria@linutronix.de
parent dbcdcb62

include/trace/events/timer.h

+20 −0
Original line number Diff line number Diff line
@@ -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"	},	\

kernel/time/timer.c

+11 −3
Original line number Diff line number Diff line
@@ -1950,7 +1950,10 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) 


	if (time_before_eq(nextevt, basej)) {

		expires = basem;

		if (base->is_idle) {

			base->is_idle = false;

			trace_timer_base_idle(false, base->cpu);

		}

	} else {

		if (base->timers_pending)

			expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
@@ -1961,8 +1964,10 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) 
		 * logic is only maintained for the BASE_STD base, deferrable

		 * timers may still see large granularity skew (by design).

		 */

		if ((expires - basem) > TICK_NSEC)

		if ((expires - basem) > TICK_NSEC && !base->is_idle) {

			base->is_idle = true;

			trace_timer_base_idle(true, base->cpu);

		}

	}

	raw_spin_unlock(&base->lock);
@@ -1984,7 +1989,10 @@ void timer_clear_idle(void) 
	 * sending the IPI a few instructions smaller for the cost of taking

	 * the lock in the exit from idle path.

	 */

	if (base->is_idle) {

		base->is_idle = false;

		trace_timer_base_idle(false, smp_processor_id());

	}

}

#endif