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From: Thomas Gleixner <tglx@linutronix.de>
To: Andrew Morton <akpm@osdl.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
	John Stultz <johnstul@us.ibm.com>,
	Arjan van de Veen <arjan@infradead.org>,
	Roman Zippel <zippel@linux-m68k.org>
Subject: [patch 18/46] clocksource: Add verification (watchdog) helper
Date: Tue, 23 Jan 2007 22:01:14 -0000	[thread overview]
Message-ID: <20070123211205.541044000@localhost.localdomain> (raw)
In-Reply-To: <20070123211159.178138000@localhost.localdomain>

[-- Attachment #1: clocksource-add-verification-helper.patch --]
[-- Type: text/plain, Size: 11075 bytes --]

From: Thomas Gleixner <tglx@linutronix.de>

The TSC needs to be verified against another clocksource. Instead of
using hardwired assumptions of available hardware, provide a generic
verification mechanism. The verification uses the best available
clocksource and handles the usability for high resolution timers /
dynticks of the clocksource which needs to be verified.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
 arch/i386/Kconfig           |    4 +
 arch/i386/kernel/tsc.c      |   49 -----------------
 include/linux/clocksource.h |   15 ++++-
 kernel/time/clocksource.c   |  125 ++++++++++++++++++++++++++++++++++++++++++--
 kernel/timer.c              |   46 ++++++++--------
 5 files changed, 161 insertions(+), 78 deletions(-)

Index: linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/tsc.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/arch/i386/kernel/tsc.c
+++ linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/tsc.c
@@ -344,49 +344,6 @@ static struct dmi_system_id __initdata b
 	 {}
 };
 
-#define TSC_FREQ_CHECK_INTERVAL (10*MSEC_PER_SEC) /* 10sec in MS */
-static struct timer_list verify_tsc_freq_timer;
-
-/* XXX - Probably should add locking */
-static void verify_tsc_freq(unsigned long unused)
-{
-	static u64 last_tsc;
-	static unsigned long last_jiffies;
-
-	u64 now_tsc, interval_tsc;
-	unsigned long now_jiffies, interval_jiffies;
-
-
-	if (check_tsc_unstable())
-		return;
-
-	rdtscll(now_tsc);
-	now_jiffies = jiffies;
-
-	if (!last_jiffies) {
-		goto out;
-	}
-
-	interval_jiffies = now_jiffies - last_jiffies;
-	interval_tsc = now_tsc - last_tsc;
-	interval_tsc *= HZ;
-	do_div(interval_tsc, cpu_khz*1000);
-
-	if (interval_tsc < (interval_jiffies * 3 / 4)) {
-		printk("TSC appears to be running slowly. "
-			"Marking it as unstable\n");
-		mark_tsc_unstable();
-		return;
-	}
-
-out:
-	last_tsc = now_tsc;
-	last_jiffies = now_jiffies;
-	/* set us up to go off on the next interval: */
-	mod_timer(&verify_tsc_freq_timer,
-		jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL));
-}
-
 /*
  * Make an educated guess if the TSC is trustworthy and synchronized
  * over all CPUs.
@@ -424,12 +381,6 @@ static int __init init_tsc_clocksource(v
 			clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
 		}
 
-		init_timer(&verify_tsc_freq_timer);
-		verify_tsc_freq_timer.function = verify_tsc_freq;
-		verify_tsc_freq_timer.expires =
-			jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL);
-		add_timer(&verify_tsc_freq_timer);
-
 		return clocksource_register(&clocksource_tsc);
 	}
 
Index: linux-2.6.20-rc4-mm1-bo/include/linux/clocksource.h
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/include/linux/clocksource.h
+++ linux-2.6.20-rc4-mm1-bo/include/linux/clocksource.h
@@ -12,11 +12,13 @@
 #include <linux/timex.h>
 #include <linux/time.h>
 #include <linux/list.h>
+#include <linux/timer.h>
 #include <asm/div64.h>
 #include <asm/io.h>
 
 /* clocksource cycle base type */
 typedef u64 cycle_t;
+struct clocksource;
 
 /**
  * struct clocksource - hardware abstraction for a free running counter
@@ -62,13 +64,22 @@ struct clocksource {
 	cycle_t cycle_last, cycle_interval;
 	u64 xtime_nsec, xtime_interval;
 	s64 error;
+
+#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
+	/* Watchdog related data, used by the framework */
+	struct list_head wd_list;
+	cycle_t wd_last;
+#endif
 };
 
 /*
  * Clock source flags bits::
  */
-#define CLOCK_SOURCE_IS_CONTINUOUS	0x01
-#define CLOCK_SOURCE_MUST_VERIFY	0x02
+#define CLOCK_SOURCE_IS_CONTINUOUS		0x01
+#define CLOCK_SOURCE_MUST_VERIFY		0x02
+
+#define CLOCK_SOURCE_WATCHDOG			0x10
+#define CLOCK_SOURCE_VALID_FOR_HRES		0x20
 
 /* simplify initialization of mask field */
 #define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL<<bits)-1) : -1)
Index: linux-2.6.20-rc4-mm1-bo/kernel/time/clocksource.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/time/clocksource.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/time/clocksource.c
@@ -62,9 +62,115 @@ static int __init clocksource_done_booti
 	finished_booting = 1;
 	return 0;
 }
-
 late_initcall(clocksource_done_booting);
 
+#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
+static LIST_HEAD(watchdog_list);
+static struct clocksource *watchdog;
+static struct timer_list watchdog_timer;
+static DEFINE_SPINLOCK(watchdog_lock);
+static cycle_t watchdog_last;
+/*
+ * Interval: 0.5sec Treshold: 0.0625s
+ */
+#define WATCHDOG_INTERVAL (HZ >> 1)
+#define WATCHDOG_TRESHOLD (NSEC_PER_SEC >> 4)
+
+static void clocksource_ratewd(struct clocksource *cs, int64_t delta)
+{
+	if (delta > -WATCHDOG_TRESHOLD && delta < WATCHDOG_TRESHOLD)
+		return;
+
+	printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
+	       cs->name, delta);
+	cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
+	clocksource_change_rating(cs, 0);
+	cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
+	list_del(&cs->wd_list);
+}
+
+static void clocksource_watchdog(unsigned long data)
+{
+	struct clocksource *cs, *tmp;
+	cycle_t csnow, wdnow;
+	int64_t wd_nsec, cs_nsec;
+
+	spin_lock(&watchdog_lock);
+
+	wdnow = watchdog->read();
+	wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);
+	watchdog_last = wdnow;
+
+	list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
+		csnow = cs->read();
+		/* Initialized ? */
+		if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
+			if ((cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
+			    (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS))
+				cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+			cs->flags |= CLOCK_SOURCE_WATCHDOG;
+			cs->wd_last = csnow;
+		} else {
+			cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask);
+			cs->wd_last = csnow;
+			/* Check the delta. Might remove from the list ! */
+			clocksource_ratewd(cs, cs_nsec - wd_nsec);
+		}
+	}
+
+	if (!list_empty(&watchdog_list)) {
+		__mod_timer(&watchdog_timer,
+			    watchdog_timer.expires + WATCHDOG_INTERVAL);
+	}
+	spin_unlock(&watchdog_lock);
+}
+static void clocksource_check_watchdog(struct clocksource *cs)
+{
+	struct clocksource *cse;
+	unsigned long flags;
+
+	spin_lock_irqsave(&watchdog_lock, flags);
+	if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
+		int started = !list_empty(&watchdog_list);
+
+		list_add(&cs->wd_list, &watchdog_list);
+		if (!started && watchdog) {
+			watchdog_last = watchdog->read();
+			watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
+			add_timer(&watchdog_timer);
+		}
+	} else if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) {
+			cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+
+		if (!watchdog || cs->rating > watchdog->rating) {
+			if (watchdog)
+				del_timer(&watchdog_timer);
+			watchdog = cs;
+			init_timer(&watchdog_timer);
+			watchdog_timer.function = clocksource_watchdog;
+
+			/* Reset watchdog cycles */
+			list_for_each_entry(cse, &watchdog_list, wd_list)
+				cse->flags &= ~CLOCK_SOURCE_WATCHDOG;
+			/* Start if list is not empty */
+			if (!list_empty(&watchdog_list)) {
+				watchdog_last = watchdog->read();
+				watchdog_timer.expires =
+					jiffies + WATCHDOG_INTERVAL;
+				add_timer(&watchdog_timer);
+			}
+		}
+	}
+	spin_unlock_irqrestore(&watchdog_lock, flags);
+}
+#else
+static void clocksource_check_watchdog(struct clocksource *cs)
+{
+	if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
+		cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+}
+#endif
+
 /**
  * clocksource_get_next - Returns the selected clocksource
  *
@@ -93,13 +199,21 @@ struct clocksource *clocksource_get_next
  */
 static struct clocksource *select_clocksource(void)
 {
+	struct clocksource *next;
+
 	if (list_empty(&clocksource_list))
 		return NULL;
 
 	if (clocksource_override)
-		return clocksource_override;
+		next = clocksource_override;
+	else
+		next = list_entry(clocksource_list.next, struct clocksource,
+				  list);
 
-	return list_entry(clocksource_list.next, struct clocksource, list);
+	if (next == curr_clocksource)
+		return NULL;
+
+	return next;
 }
 
 /*
@@ -137,13 +251,15 @@ static int clocksource_enqueue(struct cl
 int clocksource_register(struct clocksource *c)
 {
 	unsigned long flags;
-	int ret = 0;
+	int ret;
 
 	spin_lock_irqsave(&clocksource_lock, flags);
 	ret = clocksource_enqueue(c);
 	if (!ret)
 		next_clocksource = select_clocksource();
 	spin_unlock_irqrestore(&clocksource_lock, flags);
+	if (!ret)
+		clocksource_check_watchdog(c);
 	return ret;
 }
 EXPORT_SYMBOL(clocksource_register);
@@ -158,6 +274,7 @@ void clocksource_change_rating(struct cl
 
 	spin_lock_irqsave(&clocksource_lock, flags);
 	list_del(&cs->list);
+	cs->rating = rating;
 	clocksource_enqueue(cs);
 	next_clocksource = select_clocksource();
 	spin_unlock_irqrestore(&clocksource_lock, flags);
Index: linux-2.6.20-rc4-mm1-bo/kernel/timer.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/timer.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/timer.c
@@ -832,30 +832,34 @@ EXPORT_SYMBOL(do_settimeofday);
  *
  * Accumulates current time interval and initializes new clocksource
  */
-static int change_clocksource(void)
+static void change_clocksource(void)
 {
 	struct clocksource *new;
 	cycle_t now;
 	u64 nsec;
+
 	new = clocksource_get_next();
-	if (clock != new) {
-		now = clocksource_read(new);
-		nsec =  __get_nsec_offset();
-		timespec_add_ns(&xtime, nsec);
-
-		clock = new;
-		clock->cycle_last = now;
-		printk(KERN_INFO "Time: %s clocksource has been installed.\n",
-		       clock->name);
-		return 1;
-	}
-	return 0;
+
+	if (clock == new)
+		return;
+
+	now = clocksource_read(new);
+	nsec =  __get_nsec_offset();
+	timespec_add_ns(&xtime, nsec);
+
+	clock = new;
+	clock->cycle_last = now;
+
+	clock->error = 0;
+	clock->xtime_nsec = 0;
+	clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
+
+	hrtimer_clock_notify();
+	printk(KERN_INFO "Time: %s clocksource has been installed.\n",
+	       clock->name);
 }
 #else
-static inline int change_clocksource(void)
-{
-	return 0;
-}
+static inline void change_clocksource(void) { }
 #endif
 
 /**
@@ -869,7 +873,7 @@ int timekeeping_is_continuous(void)
 	do {
 		seq = read_seqbegin(&xtime_lock);
 
-		ret = clock->flags & CLOCK_SOURCE_IS_CONTINUOUS;
+		ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
 
 	} while (read_seqretry(&xtime_lock, seq));
 
@@ -1122,11 +1126,7 @@ static void update_wall_time(void)
 	clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift;
 
 	/* check to see if there is a new clocksource to use */
-	if (change_clocksource()) {
-		clock->error = 0;
-		clock->xtime_nsec = 0;
-		clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
-	}
+	change_clocksource();
 }
 
 /*
Index: linux-2.6.20-rc4-mm1-bo/arch/i386/Kconfig
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/arch/i386/Kconfig
+++ linux-2.6.20-rc4-mm1-bo/arch/i386/Kconfig
@@ -18,6 +18,10 @@ config GENERIC_TIME
 	bool
 	default y
 
+config CLOCKSOURCE_WATCHDOG
+	bool
+	default y
+
 config LOCKDEP_SUPPORT
 	bool
 	default y

--


  parent reply	other threads:[~2007-01-23 22:04 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-23 22:00 [patch 00/46] High resolution timer / dynamic tick update Thomas Gleixner
2007-01-23 22:00 ` [patch 01/46] Add irq flag to disable balancing for an interrupt Thomas Gleixner
2007-01-23 22:00 ` [patch 02/46] Add a functions to handle interrupt affinity setting Thomas Gleixner
2007-01-23 22:00 ` [patch 03/46] [RFC] HZ free ntp Thomas Gleixner
2007-01-23 22:00 ` [patch 04/46] Uninline jiffies.h functions Thomas Gleixner
2007-01-23 22:01 ` [patch 05/46] Thomas Gleixner
2007-01-23 22:01 ` [patch 06/46] Fix timeout overflow with jiffies Thomas Gleixner
2007-01-23 22:01 ` [patch 07/46] GTOD: persistent clock support Thomas Gleixner
2007-01-23 22:01 ` [patch 08/46] i386: use GTOD " Thomas Gleixner
2007-01-23 22:01 ` [patch 09/46] i386 Remove useless code in tsc.c Thomas Gleixner
2007-01-23 22:01 ` [patch 10/46] Simplify the registration of clocksources Thomas Gleixner
2007-01-23 22:01 ` [patch 11/46] x86: rewrite SMP TSC sync code Thomas Gleixner
2007-01-23 22:01 ` [patch 12/46] clocksource: replace is_continuous by a flag field Thomas Gleixner
2007-01-24 11:23   ` [patch] clocksource: fixup is_continous changes in vmitime.c Ingo Molnar
2007-01-24 11:53     ` Thomas Gleixner
2007-01-23 22:01 ` [patch 13/46] clocksource: fixup is_continous changes on ARM Thomas Gleixner
2007-01-23 22:01 ` [patch 14/46] clocksource: fixup is_continous changes on AVR32 Thomas Gleixner
2007-01-23 22:01 ` [patch 15/46] clocksource: fixup is_continous changes on S390 Thomas Gleixner
2007-01-23 22:01 ` [patch 16/46] clocksource: fixup is_continous changes on MIPS Thomas Gleixner
2007-01-23 22:01 ` [patch 17/46] clocksource: Remove the update callback Thomas Gleixner
2007-01-23 22:01 ` Thomas Gleixner [this message]
2007-01-24 15:42   ` [patch] clocksource: add verification (watchdog) helper, fix Ingo Molnar
2007-01-23 22:01 ` [patch 19/46] Mark TSC on GeodeLX reliable Thomas Gleixner
2007-01-23 22:01 ` [patch 20/46] uninline irq_enter() Thomas Gleixner
2007-01-23 22:01 ` [patch 21/46] Fix cascade lookup of next_timer_interrupt Thomas Gleixner
2007-01-23 22:01 ` [patch 22/46] Extend next_timer_interrupt() to use a reference jiffie Thomas Gleixner
2007-01-23 22:01 ` [patch 23/46] hrtimers: namespace and enum cleanup Thomas Gleixner
2007-01-23 22:01 ` [patch 24/46] hrtimers: namespace and enum cleanup vs. git-input Thomas Gleixner
2007-01-23 22:01 ` [patch 25/46] hrtimers: cleanup locking Thomas Gleixner
2007-01-23 22:01 ` [patch 26/46] hrtimers; add state tracking Thomas Gleixner
2007-01-23 22:01 ` [patch 27/46] hrtimers: clean up callback tracking Thomas Gleixner
2007-01-23 22:01 ` [patch 28/46] hrtimers: move and add documentation Thomas Gleixner
2007-01-23 22:01 ` [patch 29/46] ACPI: fix missing include for UP Thomas Gleixner
2007-01-23 22:01 ` [patch 30/46] ACPI keep track of timer broadcasting Thomas Gleixner
2007-01-23 22:01 ` [patch 31/46] Allow early access to the power management timer Thomas Gleixner
2007-01-23 22:01 ` [patch 32/46] i386, apic: clean up the APIC code Thomas Gleixner
2007-01-23 22:01 ` [patch 33/46] clockevents: add core functionality Thomas Gleixner
2007-01-23 22:01 ` [patch 34/46] tick-management: " Thomas Gleixner
2007-01-23 22:01 ` [patch 35/46] tick-management: broadcast functionality Thomas Gleixner
2007-01-23 22:01 ` [patch 36/46] tick-management: dyntick / highres functionality Thomas Gleixner
2007-01-28  2:03   ` [PATCH] high_res_timers: precisely update_process_times; " Karsten Wiese
2007-01-23 22:01 ` [patch 37/46] clockevents: i383 drivers Thomas Gleixner
2007-01-23 22:01 ` [patch 38/46] i386 rework local apic timer calibration Thomas Gleixner
2007-01-23 22:01 ` [patch 39/46] i386 prepare for dyntick Thomas Gleixner
2007-01-23 22:01 ` [patch 40/46] i386 prepare nmi watchdog for dynticks Thomas Gleixner
2007-01-23 22:01 ` [patch 41/46] i386: enable dynticks in kconfig Thomas Gleixner
2007-01-23 22:01 ` [patch 42/46] hrtimers: add high resolution timer support Thomas Gleixner
2007-01-23 22:01 ` [patch 43/46] hrtimers: prevent possible itimer DoS Thomas Gleixner
2007-01-23 22:01 ` [patch 44/46] Add debugging feature /proc/timer_stat Thomas Gleixner
2007-01-23 22:01 ` [patch 45/46] Add debugging feature /proc/timer_list Thomas Gleixner
2007-01-23 22:01 ` [patch 46/46] Add SysRq-Q to print timer_list debug info Thomas Gleixner
2007-01-24  2:16 ` [patch 00/46] High resolution timer / dynamic tick update Daniel Walker
2007-01-24  2:23   ` Andrew Morton
2007-01-24  3:25     ` Daniel Walker
2007-01-24  7:07   ` Ingo Molnar
2007-01-24  9:30     ` Daniel Walker
2007-01-24  9:51       ` Ingo Molnar
2007-01-24 10:23         ` Daniel Walker
2007-01-24 10:29           ` Ingo Molnar
2007-01-24 10:53             ` Daniel Walker
2007-01-24 11:04               ` Ingo Molnar
2007-01-24 11:13           ` Thomas Gleixner
2007-01-24 15:53             ` Daniel Walker
     [not found]               ` <20070124160046.GA24798@elte.hu>
2007-01-24 17:21                 ` Daniel Walker
     [not found]                 ` <1169655076.19471.241.camel@imap.mvista.com>
2007-01-24 19:38                   ` Ingo Molnar
2007-01-24 20:09                     ` Daniel Walker
2007-01-24 20:13                       ` Ingo Molnar
2007-01-24 19:57       ` john stultz
2007-01-24 20:51         ` Daniel Walker
2007-01-24 21:23           ` john stultz
2007-01-24 21:37             ` Daniel Walker
2007-01-25  6:10           ` Ingo Molnar
2007-01-25  6:37           ` Ingo Molnar
2007-01-25  6:32         ` Ingo Molnar
2007-01-25 16:38           ` Daniel Walker
2007-01-28  2:17 ` Andrew Morton
2007-01-29 21:31   ` john stultz
2007-01-29 21:45     ` john stultz

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