Attachment 603553 Details for Bug 836803 – RHEL PATCH 5/7

[patch] RHEL PATCH 5/7

0005-timekeeping-Provide-hrtimer-update-function.patch (text/plain), 3.40 KB, created by Prarit Bhargava on 2012-08-10 13:57:07 UTC

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Creator: Prarit Bhargava

Created: 2012-08-10 13:57:07 UTC

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patch

obsolete

>From cb0c56b49c23e074d174dd3933e58d4912efda44 Mon Sep 17 00:00:00 2001
>From: Prarit Bhargava <prarit@redhat.com>
>Date: Tue, 24 Jul 2012 10:25:35 -0400
>Subject: timekeeping: Provide hrtimer update function
>
>commit f6c06abfb3972ad4914cef57d8348fcb2932bc3b
>Author: Thomas Gleixner <tglx@linutronix.de>
>Date:   Tue Jul 10 18:43:24 2012 -0400
>
>    timekeeping: Provide hrtimer update function
>
>    To finally fix the infamous leap second issue and other race windows
>    caused by functions which change the offsets between the various time
>    bases (CLOCK_MONOTONIC, CLOCK_REALTIME and CLOCK_BOOTTIME) we need a
>    function which atomically gets the current monotonic time and updates
>    the offsets of CLOCK_REALTIME and CLOCK_BOOTTIME with minimalistic
>    overhead. The previous patch which provides ktime_t offsets allows us
>    to make this function almost as cheap as ktime_get() which is going to
>    be replaced in hrtimer_interrupt().
>
>    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>    Reviewed-by: Ingo Molnar <mingo@kernel.org>
>    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
>    Acked-by: Prarit Bhargava <prarit@redhat.com>
>    Cc: stable@vger.kernel.org
>    Signed-off-by: John Stultz <johnstul@us.ibm.com>
>    Link: http://lkml.kernel.org/r/1341960205-56738-7-git-send-email-johnstul@us.ibm.com
>    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>
>Note that RHEL6 does not have the CLOCK_REALTIME and CLOCK_BOOTTIME
>patches, so ktime_get_update_offsets() only has to be called on the real
>clock.
>---
> include/linux/hrtimer.h   |    1 +
> kernel/time/timekeeping.c |   34 ++++++++++++++++++++++++++++++++++
> 2 files changed, 35 insertions(+)
>
>diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
>index 84ce30b..248fd7f 100644
>--- a/include/linux/hrtimer.h
>+++ b/include/linux/hrtimer.h
>@@ -319,6 +319,7 @@ extern ktime_t ktime_get(void);
> extern ktime_t ktime_get_real(void);
> extern ktime_t ktime_get_boottime(void);
> extern ktime_t ktime_get_monotonic_offset(void);
>+extern ktime_t ktime_get_update_offsets(ktime_t *offs_real);
> 
> DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
> 
>diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
>index 013bafc..47fde33 100644
>--- a/kernel/time/timekeeping.c
>+++ b/kernel/time/timekeeping.c
>@@ -1253,6 +1253,40 @@ void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
> 	} while (read_seqretry(&timekeeper.lock, seq));
> }
> 
>+#ifdef CONFIG_HIGH_RES_TIMERS
>+/**
>+ * ktime_get_update_offsets - hrtimer helper
>+ * @offs_real:	pointer to storage for monotonic -> realtime offset
>+ *
>+ * Returns current monotonic time and updates the offsets
>+ * Called from hrtimer_interupt() or retrigger_next_event()
>+ *
>+ * RHEL6: We do not have real vs boot clocks in RHEL.
>+ */
>+ktime_t ktime_get_update_offsets(ktime_t *offs_real)
>+{
>+	ktime_t now;
>+	unsigned int seq;
>+	u64 secs, nsecs;
>+
>+	do {
>+		seq = read_seqbegin(&timekeeper.lock);
>+
>+		secs = timekeeper.xtime.tv_sec;
>+		nsecs = timekeeper.xtime.tv_nsec;
>+		nsecs += timekeeping_get_ns();
>+		/* If arch requires, add in gettimeoffset() */
>+		nsecs += arch_gettimeoffset();
>+
>+		*offs_real = timekeeper.offs_real;
>+	} while (read_seqretry(&timekeeper.lock, seq));
>+
>+	now = ktime_add_ns(ktime_set(secs, 0), nsecs);
>+	now = ktime_sub(now, *offs_real);
>+	return now;
>+}
>+#endif
>+
> /**
>  * xtime_update() - advances the timekeeping infrastructure
>  * @ticks:	number of ticks, that have elapsed since the last call.
>-- 
>1.7.9.3
>

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