From cb5de2f8d0306be38f9b377b8a5c56acca7dbc3d Mon Sep 17 00:00:00 2001 From: John Stultz Date: Wed, 1 Jun 2011 18:18:09 -0700 Subject: time: Catch invalid timespec sleep values in __timekeeping_inject_sleeptime MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Arve suggested making sure we catch possible negative sleep time intervals that could be passed into timekeeping_inject_sleeptime. CC: Arve Hjønnevåg CC: Thomas Gleixner Signed-off-by: John Stultz --- kernel/time/timekeeping.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'kernel') diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 342408cf68dd..9d09777a213f 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_WARN "__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); -- cgit v1.2.3 From cb33217b1b2523895eb328a0b13fb3b1c4000969 Mon Sep 17 00:00:00 2001 From: John Stultz Date: Tue, 31 May 2011 22:53:23 -0700 Subject: time: Avoid accumulating time drift in suspend/resume MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Because the read_persistent_clock interface is usually backed by only a second granular interface, each time we read from the persistent clock for suspend/resume, we introduce a half second (on average) of error. In order to avoid this error accumulating as the system is suspended over and over, this patch measures the time delta between the persistent clock and the system CLOCK_REALTIME. If the delta is less then 2 seconds from the last suspend, we compensate by using the previous time delta (keeping it close). If it is larger then 2 seconds, we assume the clock was set or has been changed, so we do no correction and update the delta. Note: If NTP is running, ths could seem to "fight" with the NTP corrected time, where as if the system time was off by 1 second, and NTP slewed the value in, a suspend/resume cycle could undo this correction, by trying to restore the previous offset from the persistent clock. However, without this patch, since each read could cause almost a full second worth of error, its possible to get almost 2 seconds of error just from the suspend/resume cycle alone, so this about equal to any offset added by the compensation. Further on systems that suspend/resume frequently, this should keep time closer then NTP could compensate for if the errors were allowed to accumulate. Credits to Arve Hjønnevåg for suggesting this solution. CC: Arve Hjønnevåg CC: Thomas Gleixner Signed-off-by: John Stultz --- kernel/time/timekeeping.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'kernel') diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 9d09777a213f..fdc6b887b208 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -692,12 +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); -- cgit v1.2.3 From cbaa51524b3224813814607177a00c350ee35d12 Mon Sep 17 00:00:00 2001 From: John Stultz Date: Wed, 20 Jul 2011 15:42:55 -0700 Subject: time: Fix stupid KERN_WARN compile issue MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Terribly embarassing. Don't know how I committed this, but its KERN_WARNING not KERN_WARN. This fixes the following compile error: kernel/time/timekeeping.c: In function ‘__timekeeping_inject_sleeptime’: kernel/time/timekeeping.c:608: error: ‘KERN_WARN’ undeclared (first use in this function) kernel/time/timekeeping.c:608: error: (Each undeclared identifier is reported only once kernel/time/timekeeping.c:608: error: for each function it appears in.) kernel/time/timekeeping.c:608: error: expected ‘)’ before string constant make[2]: *** [kernel/time/timekeeping.o] Error 1 Reported-by: Ingo Molnar Signed-off-by: John Stultz --- kernel/time/timekeeping.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index fdc6b887b208..2b021b0e8507 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -605,7 +605,7 @@ static struct timespec timekeeping_suspend_time; static void __timekeeping_inject_sleeptime(struct timespec *delta) { if (!timespec_valid(delta)) { - printk(KERN_WARN "__timekeeping_inject_sleeptime: Invalid " + printk(KERN_WARNING "__timekeeping_inject_sleeptime: Invalid " "sleep delta value!\n"); return; } -- cgit v1.2.3