Attachment 603549 Details for Bug 836803 – RHEL PATCH 1/7

[patch] RHEL PATCH 1/7

0001-hrtimer-Provide-clock_was_set_delayed.patch (text/plain), 3.76 KB, created by Prarit Bhargava on 2012-08-10 13:56:50 UTC

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Creator: Prarit Bhargava

Created: 2012-08-10 13:56:50 UTC

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patch

obsolete

>From 5b438dd24503661778362ac9f39be8b1aa409c88 Mon Sep 17 00:00:00 2001
>From: Prarit Bhargava <prarit@redhat.com>
>Date: Tue, 24 Jul 2012 10:20:33 -0400
>Subject: hrtimer: Provide clock_was_set_delayed()
>
>commit f55a6faa384304c89cfef162768e88374d3312cb
>Author: John Stultz <johnstul@us.ibm.com>
>Date:   Tue Jul 10 18:43:19 2012 -0400
>
>    hrtimer: Provide clock_was_set_delayed()
>
>    clock_was_set() cannot be called from hard interrupt context because
>    it calls on_each_cpu().
>
>    For fixing the widely reported leap seconds issue it is necessary to
>    call it from hard interrupt context, i.e. the timer tick code, which
>    does the timekeeping updates.
>
>    Provide a new function which denotes it in the hrtimer cpu base
>    structure of the cpu on which it is called and raise the hrtimer
>    softirq. We then execute the clock_was_set() notificiation from
>    softirq context in run_hrtimer_softirq(). The hrtimer softirq is
>    rarely used, so polling the flag there is not a performance issue.
>
>    [ tglx: Made it depend on CONFIG_HIGH_RES_TIMERS. We really should get
>      rid of all this ifdeffery ASAP ]
>
>    Signed-off-by: John Stultz <johnstul@us.ibm.com>
>    Reported-by: Jan Engelhardt <jengelh@inai.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
>    Link: http://lkml.kernel.org/r/1341960205-56738-2-git-send-email-johnstul@us.ibm.com
>    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>---
> include/linux/hrtimer.h |    9 +++++++++
> kernel/hrtimer.c        |   20 ++++++++++++++++++++
> 2 files changed, 29 insertions(+)
>
>diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
>index 6feef29..84ce30b 100644
>--- a/include/linux/hrtimer.h
>+++ b/include/linux/hrtimer.h
>@@ -165,6 +165,7 @@ struct hrtimer_clock_base {
>  * @nr_retries:		Total number of hrtimer interrupt retries
>  * @nr_hangs:		Total number of hrtimer interrupt hangs
>  * @max_hang_time:	Maximum time spent in hrtimer_interrupt
>+ * @clock_was_set:	Indicates that clock was set from irq context.
>  */
> struct hrtimer_cpu_base {
> 	spinlock_t			lock;
>@@ -178,6 +179,9 @@ struct hrtimer_cpu_base {
> 	unsigned long			nr_hangs;
> 	ktime_t				max_hang_time;
> #endif
>+#ifndef __GENKSYMS__
>+	unsigned int			clock_was_set;
>+#endif
> };
> 
> static inline void hrtimer_set_expires(struct hrtimer *timer, ktime_t time)
>@@ -281,6 +285,8 @@ extern void hrtimer_peek_ahead_timers(void);
> # define MONOTONIC_RES_NSEC	HIGH_RES_NSEC
> # define KTIME_MONOTONIC_RES	KTIME_HIGH_RES
> 
>+extern void clock_was_set_delayed(void);
>+
> #else
> 
> # define MONOTONIC_RES_NSEC	LOW_RES_NSEC
>@@ -301,6 +307,9 @@ static inline int hrtimer_is_hres_active(struct hrtimer *timer)
> {
> 	return 0;
> }
>+
>+static inline void clock_was_set_delayed(void) { }
>+
> #endif
> 
> extern void clock_was_set(void);
>diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
>index f58270b..6703d49 100644
>--- a/kernel/hrtimer.c
>+++ b/kernel/hrtimer.c
>@@ -669,6 +669,19 @@ static int hrtimer_switch_to_hres(void)
> 	return 1;
> }
> 
>+/*
>+ * Called from timekeeping code to reprogramm the hrtimer interrupt
>+ * device. If called from the timer interrupt context we defer it to
>+ * softirq context.
>+ */
>+void clock_was_set_delayed(void)
>+{
>+	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
>+
>+	cpu_base->clock_was_set = 1;
>+	__raise_softirq_irqoff(HRTIMER_SOFTIRQ);
>+}
>+
> #else
> 
> static inline int hrtimer_hres_active(void) { return 0; }
>@@ -1374,6 +1387,13 @@ void hrtimer_peek_ahead_timers(void)
> 
> static void run_hrtimer_softirq(struct softirq_action *h)
> {
>+	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
>+
>+	if (cpu_base->clock_was_set) {
>+		cpu_base->clock_was_set = 0;
>+		clock_was_set();
>+	}
>+
> 	hrtimer_peek_ahead_timers();
> }
> 
>-- 
>1.7.9.3
>

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