[RFC][PATCH 2/7] PM / Sleep: Use wait queue to signal "no wakeup events in progress"

Rafael J. Wysocki
2012-02-21T23:37:01Z

From: Rafael J. Wysocki <rjw@sisk.pl>

The current wakeup source deactivation code doesn't do anything when
the counter of wakeup events in progress goes down to zero, which
requires pm_get_wakeup_count() to poll that counter periodically.
Although this reduces the average time it takes to deactivate a
wakeup source, it also may lead to a substantial amount of unnecessary
polling if there are extended periods of wakeup activity. Thus it
seems reasonable to use a wait queue for signaling the "no wakeup
events in progress" condition and remove the polling.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
drivers/base/power/wakeup.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

Index: linux/drivers/base/power/wakeup.c
===================================================================
--- linux.orig/drivers/base/power/wakeup.c
+++ linux/drivers/base/power/wakeup.c
@@ -17,8 +17,6 @@

#include "power.h"

-#define TIMEOUT 100
-
/*
* If set, the suspend/hibernate code will abort transitions to a sleep state
* if wakeup events are registered during or immediately before the transition.
@@ -52,6 +50,8 @@ static void pm_wakeup_timer_fn(unsigned

static LIST_HEAD(wakeup_sources);

+static DECLARE_WAIT_QUEUE_HEAD(wakeup_count_wait_queue);
+
/**
* wakeup_source_prepare - Prepare a new wakeup source for initialization.
* @ws: Wakeup source to prepare.
@@ -442,6 +442,7 @@ EXPORT_SYMBOL_GPL(pm_stay_awake);
*/
static void wakeup_source_deactivate(struct wakeup_source *ws)
{
+ unsigned int cnt, inpr;
ktime_t duration;
ktime_t now;

@@ -476,6 +477,10 @@ static void wakeup_source_deactivate(str
* couter of wakeup events in progress simultaneously.
*/
atomic_add(MAX_IN_PROGRESS, &combined_event_count);
+
+ split_counters(&cnt, &inpr);
+ if (!inpr && waitqueue_active(&wakeup_count_wait_queue))
+ wake_up(&wakeup_count_wait_queue);
}

/**
@@ -667,14 +672,19 @@ bool pm_wakeup_pending(void)
bool pm_get_wakeup_count(unsigned int *count)
{
unsigned int cnt, inpr;
+ DEFINE_WAIT(wait);

for (;;) {
+ prepare_to_wait(&wakeup_count_wait_queue, &wait,
+ TASK_INTERRUPTIBLE);
split_counters(&cnt, &inpr);
if (inpr == 0 || signal_pending(current))
break;
pm_wakeup_update_hit_counts();
- schedule_timeout_interruptible(msecs_to_jiffies(TIMEOUT));
+
+ schedule();
}
+ finish_wait(&wakeup_count_wait_queue, &wait);

split_counters(&cnt, &inpr);
*count = cnt;