PM / Sleep: Print last wakeup source on failed wakeup_count write

Commit a938da06 introduced a useful little log message to tell
users/debuggers which wakeup source aborted a suspend.  However,
this message is only printed if the abort happens during the
in-kernel suspend path (after writing /sys/power/state).

The full specification of the /sys/power/wakeup_count facility
allows user-space power managers to double-check if wakeups have
already happened before it actually tries to suspend (e.g. while it
was running user-space pre-suspend hooks), by writing the last known
wakeup_count value to /sys/power/wakeup_count.  This patch changes
the sysfs handler for that node to also print said log message if
that write fails, so that we can figure out the offending wakeup
source for both kinds of suspend aborts.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/wakeup.c

@@ -659,7 +659,7 @@ void pm_wakeup_event(struct device *dev, unsigned int msec)
 }
 EXPORT_SYMBOL_GPL(pm_wakeup_event);
 
-static void print_active_wakeup_sources(void)
+void pm_print_active_wakeup_sources(void)
 {
 	struct wakeup_source *ws;
 	int active = 0;
@@ -683,6 +683,7 @@ static void print_active_wakeup_sources(void)
 			last_activity_ws->name);
 	rcu_read_unlock();
 }
+EXPORT_SYMBOL_GPL(pm_print_active_wakeup_sources);
 
 /**
  * pm_wakeup_pending - Check if power transition in progress should be aborted.
@@ -709,7 +710,7 @@ bool pm_wakeup_pending(void)
 
 	if (ret) {
 		pr_info("PM: Wakeup pending, aborting suspend\n");
-		print_active_wakeup_sources();
+		pm_print_active_wakeup_sources();
 	}
 
 	return ret;

include/linux/suspend.h

@@ -363,6 +363,7 @@ extern bool pm_wakeup_pending(void);
 extern bool pm_get_wakeup_count(unsigned int *count, bool block);
 extern bool pm_save_wakeup_count(unsigned int count);
 extern void pm_wakep_autosleep_enabled(bool set);
+extern void pm_print_active_wakeup_sources(void);
 
 static inline void lock_system_sleep(void)
 {

kernel/power/main.c

@@ -424,6 +424,8 @@ static ssize_t wakeup_count_store(struct kobject *kobj,
 	if (sscanf(buf, "%u", &val) == 1) {
 		if (pm_save_wakeup_count(val))
 			error = n;
+		else
+			pm_print_active_wakeup_sources();
 	}
 
  out: