linux-kernel - [PATCH 3.13 063/163] alarmtimer: Return relative times in timer

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Message-Id: <1412888588-26755-64-git-send-email-kamal@canonical.com>
Date:	Thu,  9 Oct 2014 14:01:28 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Richard Cochran <richardcochran@...il.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Sharvil Nanavati <sharvil@...gle.com>,
	Richard Larocque <rlarocque@...gle.com>,
	John Stultz <john.stultz@...aro.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13 063/163] alarmtimer: Return relative times in timer_gettime

3.13.11.9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Richard Larocque <rlarocque@...gle.com>

commit e86fea764991e00a03ff1e56409ec9cacdbda4c9 upstream.

Returns the time remaining for an alarm timer, rather than the time at
which it is scheduled to expire.  If the timer has already expired or it
is not currently scheduled, the it_value's members are set to zero.

This new behavior matches that of the other posix-timers and the POSIX
specifications.

This is a change in user-visible behavior, and may break existing
applications.  Hopefully, few users rely on the old incorrect behavior.

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Richard Cochran <richardcochran@...il.com>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Sharvil Nanavati <sharvil@...gle.com>
Signed-off-by: Richard Larocque <rlarocque@...gle.com>
[jstultz: minor style tweak]
Signed-off-by: John Stultz <john.stultz@...aro.org>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 kernel/time/alarmtimer.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index fe75444..6745174 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -541,18 +541,22 @@ static int alarm_timer_create(struct k_itimer *new_timer)
  * @new_timer: k_itimer pointer
  * @cur_setting: itimerspec data to fill
  *
- * Copies the itimerspec data out from the k_itimer
+ * Copies out the current itimerspec data
  */
 static void alarm_timer_get(struct k_itimer *timr,
 				struct itimerspec *cur_setting)
 {
-	memset(cur_setting, 0, sizeof(struct itimerspec));
+	ktime_t relative_expiry_time =
+		alarm_expires_remaining(&(timr->it.alarm.alarmtimer));
 
-	cur_setting->it_interval =
-			ktime_to_timespec(timr->it.alarm.interval);
-	cur_setting->it_value =
-		ktime_to_timespec(timr->it.alarm.alarmtimer.node.expires);
-	return;
+	if (ktime_to_ns(relative_expiry_time) > 0) {
+		cur_setting->it_value = ktime_to_timespec(relative_expiry_time);
+	} else {
+		cur_setting->it_value.tv_sec = 0;
+		cur_setting->it_value.tv_nsec = 0;
+	}
+
+	cur_setting->it_interval = ktime_to_timespec(timr->it.alarm.interval);
 }
 
 /**
-- 
1.9.1

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