From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrew Morton <akpm@linux-foundation.org>
Subject: [GIT PULL] timer fix
Date: Sat, 26 Oct 2013 14:27:08 +0200 [thread overview]
Message-ID: <20131026122708.GA25259@gmail.com> (raw)
Linus,
Please pull the latest timers-urgent-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-urgent-for-linus
# HEAD: 97b9410643475d6557d2517c2aff9fd2221141a9 clockevents: Sanitize ticks to nsec conversion
This tree contains a clockevents regression fix for certain ARM
subarchitectures.
Thanks,
Ingo
------------------>
Thomas Gleixner (1):
clockevents: Sanitize ticks to nsec conversion
kernel/time/clockevents.c | 65 ++++++++++++++++++++++++++++++++++++-----------
1 file changed, 50 insertions(+), 15 deletions(-)
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 38959c8..662c579 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -33,29 +33,64 @@ struct ce_unbind {
int res;
};
-/**
- * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
- * @latch: value to convert
- * @evt: pointer to clock event device descriptor
- *
- * Math helper, returns latch value converted to nanoseconds (bound checked)
- */
-u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
+static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
+ bool ismax)
{
u64 clc = (u64) latch << evt->shift;
+ u64 rnd;
if (unlikely(!evt->mult)) {
evt->mult = 1;
WARN_ON(1);
}
+ rnd = (u64) evt->mult - 1;
+
+ /*
+ * Upper bound sanity check. If the backwards conversion is
+ * not equal latch, we know that the above shift overflowed.
+ */
+ if ((clc >> evt->shift) != (u64)latch)
+ clc = ~0ULL;
+
+ /*
+ * Scaled math oddities:
+ *
+ * For mult <= (1 << shift) we can safely add mult - 1 to
+ * prevent integer rounding loss. So the backwards conversion
+ * from nsec to device ticks will be correct.
+ *
+ * For mult > (1 << shift), i.e. device frequency is > 1GHz we
+ * need to be careful. Adding mult - 1 will result in a value
+ * which when converted back to device ticks can be larger
+ * than latch by up to (mult - 1) >> shift. For the min_delta
+ * calculation we still want to apply this in order to stay
+ * above the minimum device ticks limit. For the upper limit
+ * we would end up with a latch value larger than the upper
+ * limit of the device, so we omit the add to stay below the
+ * device upper boundary.
+ *
+ * Also omit the add if it would overflow the u64 boundary.
+ */
+ if ((~0ULL - clc > rnd) &&
+ (!ismax || evt->mult <= (1U << evt->shift)))
+ clc += rnd;
do_div(clc, evt->mult);
- if (clc < 1000)
- clc = 1000;
- if (clc > KTIME_MAX)
- clc = KTIME_MAX;
- return clc;
+ /* Deltas less than 1usec are pointless noise */
+ return clc > 1000 ? clc : 1000;
+}
+
+/**
+ * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
+ * @latch: value to convert
+ * @evt: pointer to clock event device descriptor
+ *
+ * Math helper, returns latch value converted to nanoseconds (bound checked)
+ */
+u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
+{
+ return cev_delta2ns(latch, evt, false);
}
EXPORT_SYMBOL_GPL(clockevent_delta2ns);
@@ -380,8 +415,8 @@ void clockevents_config(struct clock_event_device *dev, u32 freq)
sec = 600;
clockevents_calc_mult_shift(dev, freq, sec);
- dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);
- dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);
+ dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
+ dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
}
/**
next reply other threads:[~2013-10-26 12:27 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-26 12:27 Ingo Molnar [this message]
-- strict thread matches above, loose matches on Subject: below --
2024-05-10 11:12 [GIT PULL] timer fix Ingo Molnar
2024-05-10 17:29 ` pr-tracker-bot
2020-06-28 18:39 Ingo Molnar
2020-06-28 22:05 ` pr-tracker-bot
2020-04-25 10:16 Ingo Molnar
2020-04-25 19:30 ` pr-tracker-bot
2019-11-16 21:38 Ingo Molnar
2019-11-17 0:35 ` pr-tracker-bot
2019-10-02 22:06 Ingo Molnar
2019-10-02 23:00 ` pr-tracker-bot
2019-09-26 20:18 Ingo Molnar
2019-09-26 23:00 ` pr-tracker-bot
2019-04-12 13:09 Ingo Molnar
2019-04-13 4:05 ` pr-tracker-bot
2018-12-21 12:34 Ingo Molnar
2018-12-21 19:30 ` pr-tracker-bot
2018-12-23 19:29 ` Heiko Carstens
2019-01-17 9:51 ` Ingo Molnar
2019-01-17 15:58 ` Heiko Carstens
2019-01-17 16:57 ` Thomas Gleixner
2018-03-25 9:00 Ingo Molnar
2017-09-24 11:25 Ingo Molnar
2017-08-26 7:17 Ingo Molnar
2017-07-21 10:21 Ingo Molnar
2017-05-12 7:35 Ingo Molnar
2017-01-18 9:37 Ingo Molnar
2016-12-23 22:53 Ingo Molnar
2016-10-18 11:18 Ingo Molnar
2016-07-13 12:58 Ingo Molnar
2016-04-23 11:34 Ingo Molnar
2015-08-14 7:13 Ingo Molnar
2015-07-18 3:06 Ingo Molnar
2015-02-06 18:38 Ingo Molnar
2014-03-29 18:44 Ingo Molnar
2014-01-15 18:27 Ingo Molnar
2013-09-18 16:22 Ingo Molnar
2011-10-17 1:39 Linux 3.1-rc9 Linus Torvalds
2011-10-17 10:34 ` Peter Zijlstra
2011-10-17 14:57 ` Linus Torvalds
2011-10-17 17:54 ` Peter Zijlstra
2011-10-17 18:31 ` Linus Torvalds
2011-10-17 19:23 ` Peter Zijlstra
2011-10-17 21:00 ` Thomas Gleixner
2011-10-18 8:39 ` Thomas Gleixner
2011-10-18 9:05 ` Peter Zijlstra
2011-10-18 14:59 ` Linus Torvalds
2011-10-18 18:14 ` [GIT PULL] timer fix Ingo Molnar
2011-04-29 18:11 Ingo Molnar
2011-02-28 17:39 Ingo Molnar
2011-02-15 17:06 Ingo Molnar
2010-01-31 17:26 Ingo Molnar
2009-10-02 12:38 Ingo Molnar
2009-09-26 12:27 Ingo Molnar
2009-08-09 16:09 Ingo Molnar
2009-08-04 19:04 Ingo Molnar
2009-06-20 16:55 Ingo Molnar
2009-02-17 16:38 [git pull] " Ingo Molnar
2009-02-04 19:25 Ingo Molnar
2009-02-04 22:11 ` Linus Torvalds
2009-02-04 22:16 ` Linus Torvalds
2009-02-04 22:25 ` Ingo Molnar
2009-02-04 22:58 ` Ingo Molnar
2009-02-04 23:13 ` H. Peter Anvin
2009-02-05 0:04 ` Ingo Molnar
2009-02-05 7:51 ` Kirill Korotaev
2009-02-05 9:58 ` Pavel Emelyanov
2009-02-05 14:30 ` Ingo Molnar
2009-02-05 16:04 ` Ray Lee
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