linux-kernel - [PATCH] PM / suspend: Catch wake-up requests in suspend

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Date:	Tue, 30 Sep 2014 17:20:02 -0500
From:	Joe Swantek <joseph.swantek@...il.com>
To:	rjw@...ysocki.net
Cc:	pavel@....cz, len.brown@...el.com, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Joe Swantek <jswantek@...orola.com>
Subject: [PATCH] PM / suspend: Catch wake-up requests in suspend_again

It is possible during the processing of suspend_again() that a
wake-up request (i.e. pm_stay_awake()) be made by a driver in response
to an outside event (i.e. hw interrupt, etc.). Currently, when
suspend_again() requests to re-enter suspend, suspend_enter() runs
to re-enter suspend. The pm_wakeup_pending() function is called to check
for any wake-up requests. However, this function is essentially disabled
because the events_check_enabled flag is set to false by the previous
run through suspend_enter(). This causes any wake-up request made
during the processing of suspend_again() to be delayed until the next
time the kernel resumes sometime in the future.

To resolve this issue, if suspend_again() votes to re-enter
suspend_enter() the count of wake-up requests is re-evaluated
and the events_check_enabled flag set correctly based on the
presence of wake-up requests that occurred during suspend_again().

Signed-off-by: Joe Swantek <jswantek@...orola.com>
---
 kernel/power/suspend.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 18c6219..f619492 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -188,8 +188,25 @@ static void platform_suspend_recover(suspend_state_t state)

 static bool platform_suspend_again(suspend_state_t state)
 {
-	return state != PM_SUSPEND_FREEZE && suspend_ops->suspend_again ?
+	int count;
+	bool suspend = state != PM_SUSPEND_FREEZE &&
+		suspend_ops->suspend_again ?
 		suspend_ops->suspend_again() : false;
+
+	if (suspend) {
+		/*
+		 * pm_get_wakeup_count() gets an updated count of wakeup events
+		 * that have occured and will return false (i.e. abort suspend)
+		 * if a wakeup event has been started during suspend_again() and
+		 * is still active. pm_save_wakeup_count() stores the count
+		 * and enables pm_wakeup_pending() to properly analyze wakeup
+		 * events before entering suspend in suspend_enter().
+		 */
+		suspend = pm_get_wakeup_count(&count, false) &&
+			  pm_save_wakeup_count(count);
+	}
+
+	return suspend;
 }

 static int suspend_test(int level)
-- 
1.9.1

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