linux-kernel - [PATCH 1/6] [RFC] suspend: Block suspend when wakeups are in-progress

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Date:	Mon, 26 Sep 2011 12:13:49 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, arve@...roid.com,
	markgross@...gnar.org, Alan Stern <stern@...land.harvard.edu>,
	amit.kucheria@...aro.org, farrowg@...ibm.com,
	"Dmitry Fink (Palm GBU)" <Dmitry.Fink@...m.com>,
	linux-pm@...ts.linux-foundation.org, khilman@...com,
	Magnus Damm <damm@...nsource.se>, mjg@...hat.com,
	peterz@...radead.org
Subject: [PATCH 1/6] [RFC] suspend: Block suspend when wakeups are in-progress

With the current pm_stay_awake/pm_relax api, reads to
/sys/power/wakeup_count will block when pm_stay_awake() has been
called. Then once pm_relax() returns, the read will unblock and return
the wakeup_count value. This value can be echo'ed back into wakeup_count,
and if no other wakeup events have occured, the system can be suspended
by calling "echo mem > /sys/power/state".

This method is somewhat advisory, as if a wakeup event has occured
between the reading of /sys/power/wakeup_count and the attempt to suspend,
that attempt to suspend will fail. However, if a second attmept to suspend
is tried, without checking /sys/power/wakeup_count, the suspend will
succeed.

Similarly, if pm_stay_awake() has been called, and then a suspend is
attepted wihtout checking /sys/power/wakeup_count, the suspend will
succeed, despite the pm_relax() call not having been made.

This patch tries to make the pm_stay_awake() call a bit more enforcing,
such that any attempt to suspend that occurs while a wakeup is in progress
will fail. Once the matching pm_relax() has been called, suspend will
succeed.

This does not change the blocking behavior of /sys/power/wakeup_count,
or the suspend failure if a stale wakeup count has been echo'ed into
the /sys/power/wakeup_count.

Also modified the hibernate path in the same way.

CC: Rafael J. Wysocki <rjw@...k.pl>
CC: arve@...roid.com
CC: markgross@...gnar.org
CC: Alan Stern <stern@...land.harvard.edu>
CC: amit.kucheria@...aro.org
CC: farrowg@...ibm.com
CC: Dmitry Fink (Palm GBU) <Dmitry.Fink@...m.com>
CC: linux-pm@...ts.linux-foundation.org
CC: khilman@...com
CC: Magnus Damm <damm@...nsource.se>
CC: mjg@...hat.com 
CC: peterz@...radead.org 
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 drivers/base/power/wakeup.c |   13 +++++++++++++
 include/linux/suspend.h     |    3 +++
 kernel/power/hibernate.c    |    5 +++++
 kernel/power/suspend.c      |    5 +++++
 4 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index 84f7c7d..0722873 100644
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -580,6 +580,19 @@ static void pm_wakeup_update_hit_counts(void)
 	rcu_read_unlock();
 }
 
+
+bool pm_wakeup_in_progress(void)
+{
+	unsigned int cnt, inpr;
+	unsigned long flags;
+
+	spin_lock_irqsave(&events_lock, flags);
+	split_counters(&cnt, &inpr);
+	spin_unlock_irqrestore(&events_lock, flags);
+
+	return (inpr != 0);
+}
+
 /**
  * pm_wakeup_pending - Check if power transition in progress should be aborted.
  *
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 6bbcef2..c9403a1 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -294,6 +294,7 @@ extern int unregister_pm_notifier(struct notifier_block *nb);
 extern bool events_check_enabled;
 
 extern bool pm_wakeup_pending(void);
+extern bool pm_wakeup_in_progress(void);
 extern bool pm_get_wakeup_count(unsigned int *count);
 extern bool pm_save_wakeup_count(unsigned int count);
 #else /* !CONFIG_PM_SLEEP */
@@ -311,6 +312,8 @@ static inline int unregister_pm_notifier(struct notifier_block *nb)
 #define pm_notifier(fn, pri)	do { (void)(fn); } while (0)
 
 static inline bool pm_wakeup_pending(void) { return false; }
+static inline bool pm_wakeup_in_progress(void) { return false; }
+
 #endif /* !CONFIG_PM_SLEEP */
 
 extern struct mutex pm_mutex;
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 8f7b1db..22dc22c 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -611,6 +611,11 @@ int hibernate(void)
 		goto Unlock;
 	}
 
+	if (pm_wakeup_in_progress()) {
+		error = -EBUSY;
+		goto Unlock;
+	}
+
 	pm_prepare_console();
 	error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
 	if (error)
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index b6b71ad..b2dba52 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -281,6 +281,11 @@ int enter_state(suspend_state_t state)
 	if (!mutex_trylock(&pm_mutex))
 		return -EBUSY;
 
+	if (pm_wakeup_in_progress()) {
+		error = -EBUSY;
+		goto Unlock;
+	}
+
 	printk(KERN_INFO "PM: Syncing filesystems ... ");
 	sys_sync();
 	printk("done.\n");
-- 
1.7.3.2.146.gca209

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