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Message-ID: <20110722141428.GA9650@elte.hu>
Date: Fri, 22 Jul 2011 16:14:28 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
John Stultz <johnstul@...ibm.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] timers/core changes for v3.1
Linus,
Please pull the latest timers-core-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git timers-core-for-linus
Thanks,
Ingo
------------------>
John Stultz (4):
time: Catch invalid timespec sleep values in __timekeeping_inject_sleeptime
time: Avoid accumulating time drift in suspend/resume
rtc: Avoid accumulating time drift in suspend/resume
time: Fix stupid KERN_WARN compile issue
drivers/rtc/class.c | 65 +++++++++++++++++++++++++++++++++------------
kernel/time/timekeeping.c | 28 +++++++++++++++++++
2 files changed, 76 insertions(+), 17 deletions(-)
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 4194e59..01a7df5 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -41,20 +41,41 @@ static void rtc_device_release(struct device *dev)
* system's wall clock; restore it on resume().
*/
-static time_t oldtime;
-static struct timespec oldts;
+static struct timespec old_rtc, old_system, old_delta;
+
static int rtc_suspend(struct device *dev, pm_message_t mesg)
{
struct rtc_device *rtc = to_rtc_device(dev);
struct rtc_time tm;
-
+ struct timespec delta, delta_delta;
if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
return 0;
+ /* snapshot the current RTC and system time at suspend*/
rtc_read_time(rtc, &tm);
- ktime_get_ts(&oldts);
- rtc_tm_to_time(&tm, &oldtime);
+ getnstimeofday(&old_system);
+ rtc_tm_to_time(&tm, &old_rtc.tv_sec);
+
+
+ /*
+ * To avoid drift caused by repeated suspend/resumes,
+ * which each can add ~1 second drift error,
+ * try to compensate so the difference in system time
+ * and rtc time stays close to constant.
+ */
+ delta = timespec_sub(old_system, old_rtc);
+ delta_delta = timespec_sub(delta, old_delta);
+ if (abs(delta_delta.tv_sec) >= 2) {
+ /*
+ * if delta_delta is too large, assume time correction
+ * has occured and set old_delta to the current delta.
+ */
+ old_delta = delta;
+ } else {
+ /* Otherwise try to adjust old_system to compensate */
+ old_system = timespec_sub(old_system, delta_delta);
+ }
return 0;
}
@@ -63,32 +84,42 @@ static int rtc_resume(struct device *dev)
{
struct rtc_device *rtc = to_rtc_device(dev);
struct rtc_time tm;
- time_t newtime;
- struct timespec time;
- struct timespec newts;
+ struct timespec new_system, new_rtc;
+ struct timespec sleep_time;
if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
return 0;
- ktime_get_ts(&newts);
+ /* snapshot the current rtc and system time at resume */
+ getnstimeofday(&new_system);
rtc_read_time(rtc, &tm);
if (rtc_valid_tm(&tm) != 0) {
pr_debug("%s: bogus resume time\n", dev_name(&rtc->dev));
return 0;
}
- rtc_tm_to_time(&tm, &newtime);
- if (newtime <= oldtime) {
- if (newtime < oldtime)
+ rtc_tm_to_time(&tm, &new_rtc.tv_sec);
+ new_rtc.tv_nsec = 0;
+
+ if (new_rtc.tv_sec <= old_rtc.tv_sec) {
+ if (new_rtc.tv_sec < old_rtc.tv_sec)
pr_debug("%s: time travel!\n", dev_name(&rtc->dev));
return 0;
}
- /* calculate the RTC time delta */
- set_normalized_timespec(&time, newtime - oldtime, 0);
- /* subtract kernel time between rtc_suspend to rtc_resume */
- time = timespec_sub(time, timespec_sub(newts, oldts));
+ /* calculate the RTC time delta (sleep time)*/
+ sleep_time = timespec_sub(new_rtc, old_rtc);
+
+ /*
+ * Since these RTC suspend/resume handlers are not called
+ * at the very end of suspend or the start of resume,
+ * some run-time may pass on either sides of the sleep time
+ * so subtract kernel run-time between rtc_suspend to rtc_resume
+ * to keep things accurate.
+ */
+ sleep_time = timespec_sub(sleep_time,
+ timespec_sub(new_system, old_system));
- timekeeping_inject_sleeptime(&time);
+ timekeeping_inject_sleeptime(&sleep_time);
return 0;
}
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 342408c..2b021b0e 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -604,6 +604,12 @@ static struct timespec timekeeping_suspend_time;
*/
static void __timekeeping_inject_sleeptime(struct timespec *delta)
{
+ if (!timespec_valid(delta)) {
+ printk(KERN_WARNING "__timekeeping_inject_sleeptime: Invalid "
+ "sleep delta value!\n");
+ return;
+ }
+
xtime = timespec_add(xtime, *delta);
wall_to_monotonic = timespec_sub(wall_to_monotonic, *delta);
total_sleep_time = timespec_add(total_sleep_time, *delta);
@@ -686,12 +692,34 @@ static void timekeeping_resume(void)
static int timekeeping_suspend(void)
{
unsigned long flags;
+ struct timespec delta, delta_delta;
+ static struct timespec old_delta;
read_persistent_clock(&timekeeping_suspend_time);
write_seqlock_irqsave(&xtime_lock, flags);
timekeeping_forward_now();
timekeeping_suspended = 1;
+
+ /*
+ * To avoid drift caused by repeated suspend/resumes,
+ * which each can add ~1 second drift error,
+ * try to compensate so the difference in system time
+ * and persistent_clock time stays close to constant.
+ */
+ delta = timespec_sub(xtime, timekeeping_suspend_time);
+ delta_delta = timespec_sub(delta, old_delta);
+ if (abs(delta_delta.tv_sec) >= 2) {
+ /*
+ * if delta_delta is too large, assume time correction
+ * has occured and set old_delta to the current delta.
+ */
+ old_delta = delta;
+ } else {
+ /* Otherwise try to adjust old_system to compensate */
+ timekeeping_suspend_time =
+ timespec_add(timekeeping_suspend_time, delta_delta);
+ }
write_sequnlock_irqrestore(&xtime_lock, flags);
clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
--
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