linux-kernel - [PATCH] PM-runtime: add tracepoints for usage

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Date:   Sat, 04 Jan 2020 17:27:57 +0100
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] PM-runtime: add tracepoints for usage_count changes

Add tracepoints to remaining places where device's power.usage_count
is changed. This helps debugging where and why autosuspend is prevented.

Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
---
 drivers/base/power/runtime.c | 13 +++++++++++--
 include/trace/events/rpm.h   |  6 ++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 48616f358854..16134a69bf6f 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1006,8 +1006,10 @@ int __pm_runtime_idle(struct device *dev, int rpmflags)
 	int retval;
 
 	if (rpmflags & RPM_GET_PUT) {
-		if (!atomic_dec_and_test(&dev->power.usage_count))
+		if (!atomic_dec_and_test(&dev->power.usage_count)) {
+			trace_rpm_usage_rcuidle(dev, rpmflags);
 			return 0;
+		}
 	}
 
 	might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe);
@@ -1038,8 +1040,10 @@ int __pm_runtime_suspend(struct device *dev, int rpmflags)
 	int retval;
 
 	if (rpmflags & RPM_GET_PUT) {
-		if (!atomic_dec_and_test(&dev->power.usage_count))
+		if (!atomic_dec_and_test(&dev->power.usage_count)) {
+			trace_rpm_usage_rcuidle(dev, rpmflags);
 			return 0;
+		}
 	}
 
 	might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe);
@@ -1101,6 +1105,7 @@ int pm_runtime_get_if_in_use(struct device *dev)
 	retval = dev->power.disable_depth > 0 ? -EINVAL :
 		dev->power.runtime_status == RPM_ACTIVE
 			&& atomic_inc_not_zero(&dev->power.usage_count);
+	trace_rpm_usage_rcuidle(dev, 0);
 	spin_unlock_irqrestore(&dev->power.lock, flags);
 	return retval;
 }
@@ -1434,6 +1439,8 @@ void pm_runtime_allow(struct device *dev)
 	dev->power.runtime_auto = true;
 	if (atomic_dec_and_test(&dev->power.usage_count))
 		rpm_idle(dev, RPM_AUTO | RPM_ASYNC);
+	else
+		trace_rpm_usage_rcuidle(dev, RPM_AUTO | RPM_ASYNC);
 
  out:
 	spin_unlock_irq(&dev->power.lock);
@@ -1501,6 +1508,8 @@ static void update_autosuspend(struct device *dev, int old_delay, int old_use)
 		if (!old_use || old_delay >= 0) {
 			atomic_inc(&dev->power.usage_count);
 			rpm_resume(dev, 0);
+		} else {
+			trace_rpm_usage_rcuidle(dev, 0);
 		}
 	}
 
diff --git a/include/trace/events/rpm.h b/include/trace/events/rpm.h
index 26927a560eab..3c716214dab1 100644
--- a/include/trace/events/rpm.h
+++ b/include/trace/events/rpm.h
@@ -74,6 +74,12 @@ DEFINE_EVENT(rpm_internal, rpm_idle,
 
 	TP_ARGS(dev, flags)
 );
+DEFINE_EVENT(rpm_internal, rpm_usage,
+
+	TP_PROTO(struct device *dev, int flags),
+
+	TP_ARGS(dev, flags)
+);
 
 TRACE_EVENT(rpm_return_int,
 	TP_PROTO(struct device *dev, unsigned long ip, int ret),
-- 
2.20.1