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Subject[PATCH 4/8] PM / Sleep: Use wait queue to signal "no wakeup events in progress"
Date
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 | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 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_create - Create a struct wakeup_source object.
* @name: Name of the new wakeup source.
@@ -84,7 +84,7 @@ void wakeup_source_destroy(struct wakeup
while (ws->active) {
spin_unlock_irq(&ws->lock);

- schedule_timeout_interruptible(msecs_to_jiffies(TIMEOUT));
+ schedule_timeout_interruptible(msecs_to_jiffies(100));

spin_lock_irq(&ws->lock);
}
@@ -411,6 +411,7 @@ 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;

@@ -444,6 +445,10 @@ 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)
+ wake_up_all(&wakeup_count_wait_queue);
}

/**
@@ -624,14 +629,19 @@ 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;


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