Attachment 603991 Details for Bug 840949 – RHEL PATCH 1/3

[patch] RHEL PATCH 1/3

0001-RHEL6.2.z-PATCH-BZ-847365-1-3-ntp-Add-ntp_lock-to-re.patch (text/plain), 5.11 KB, created by Prarit Bhargava on 2012-08-13 12:55:03 UTC

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Creator: Prarit Bhargava

Created: 2012-08-13 12:55:03 UTC

Size: 5.11 KB

patch

obsolete

>From 302342d0f16535391daad3aa4f8e5a090bb3e056 Mon Sep 17 00:00:00 2001
>From: Prarit Bhargava <prarit@redhat.com>
>Date: Mon, 16 Jul 2012 14:32:42 -0400
>Subject: [PATCH 1/3] [RHEL6.2.z PATCH BZ 847365 1/3] ntp: Add ntp_lock to
> replace xtime_locking
>
>Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=840949
>Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=847365
>
>commit bd3312681f69207a40431981c1bce1afdc9b7975
>Author: John Stultz <john.stultz@linaro.org>
>Date:   Mon Nov 14 13:48:36 2011 -0800
>
>ntp: Add ntp_lock to replace xtime_locking
>
>Use a ntp_lock spin lock to replace xtime_lock locking in ntp.c
>
>	CC: Thomas Gleixner <tglx@linutronix.de>
>	CC: Eric Dumazet <eric.dumazet@gmail.com>
>	CC: Richard Cochran <richardcochran@gmail.com>
>	Signed-off-by: John Stultz <john.stultz@linaro.org>
>
>The upstream code had previously moved the xtime struct into the
>timekeeper struct and protected the xtime update with the timekeeper lock.
>However, that is too large of a patch for z-stream so the solution is to
>restore the xtime_lock locking in the timekeeping_leap_insert() function
>and mimic upstream.  Obviously, this chunk is RHEL only.
>---
> kernel/time/ntp.c         |   43 +++++++++++++++++++++++++++++++------------
> kernel/time/timekeeping.c |    4 +++-
> 2 files changed, 34 insertions(+), 13 deletions(-)
>
>diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
>index 4800f93..85c4100 100644
>--- a/kernel/time/ntp.c
>+++ b/kernel/time/ntp.c
>@@ -19,6 +19,9 @@
>  * NTP timekeeping variables:
>  */
> 
>+DEFINE_SPINLOCK(ntp_lock);
>+
>+
> /* USER_HZ period (usecs): */
> unsigned long			tick_usec = TICK_USEC;
> 
>@@ -163,11 +166,13 @@ static void ntp_update_offset(long offset)
> 
> /**
>  * ntp_clear - Clears the NTP state variables
>- *
>- * Must be called while holding a write on the xtime_lock
>  */
> void ntp_clear(void)
> {
>+	unsigned long flags;
>+
>+	spin_lock_irqsave(&ntp_lock, flags);
>+
> 	time_adjust	= 0;		/* stop active adjtime() */
> 	time_status	|= STA_UNSYNC;
> 	time_maxerror	= NTP_PHASE_LIMIT;
>@@ -177,6 +182,8 @@ void ntp_clear(void)
> 
> 	tick_length	= tick_length_base;
> 	time_offset	= 0;
>+	spin_unlock_irqrestore(&ntp_lock, flags);
>+
> }
> 
> /*
>@@ -187,14 +194,15 @@ void ntp_clear(void)
> static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
> {
> 	enum hrtimer_restart res = HRTIMER_NORESTART;
>+	unsigned long flags;
>+	int leap = 0;
> 
>-	write_seqlock(&xtime_lock);
>-
>+	spin_lock_irqsave(&ntp_lock, flags);
> 	switch (time_state) {
> 	case TIME_OK:
> 		break;
> 	case TIME_INS:
>-		timekeeping_leap_insert(-1);
>+		leap = -1;
> 		time_state = TIME_OOP;
> 		printk(KERN_NOTICE
> 			"Clock: inserting leap second 23:59:60 UTC\n");
>@@ -202,7 +210,7 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
> 		res = HRTIMER_RESTART;
> 		break;
> 	case TIME_DEL:
>-		timekeeping_leap_insert(1);
>+		leap = 1;
> 		time_tai--;
> 		time_state = TIME_WAIT;
> 		printk(KERN_NOTICE
>@@ -217,8 +225,14 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
> 			time_state = TIME_OK;
> 		break;
> 	}
>+	spin_unlock_irqrestore(&ntp_lock, flags);
> 
>-	write_sequnlock(&xtime_lock);
>+	/*
>+	 * We have to call this outside of the ntp_lock to keep
>+	 * the proper locking hierarchy
>+	 */
>+	if (leap)
>+		timekeeping_leap_insert(leap);
> 
> 	return res;
> }
>@@ -234,6 +248,9 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
> void second_overflow(void)
> {
> 	s64 delta;
>+	unsigned long flags;
>+
>+	spin_lock_irqsave(&ntp_lock, flags);
> 
> 	/* Bump the maxerror field */
> 	time_maxerror += MAXFREQ / NSEC_PER_USEC;
>@@ -253,23 +270,25 @@ void second_overflow(void)
> 	tick_length	+= delta;
> 
> 	if (!time_adjust)
>-		return;
>+		goto out;
> 
> 	if (time_adjust > MAX_TICKADJ) {
> 		time_adjust -= MAX_TICKADJ;
> 		tick_length += MAX_TICKADJ_SCALED;
>-		return;
>+		goto out;
> 	}
> 
> 	if (time_adjust < -MAX_TICKADJ) {
> 		time_adjust += MAX_TICKADJ;
> 		tick_length -= MAX_TICKADJ_SCALED;
>-		return;
>+		goto out;
> 	}
> 
> 	tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
> 							 << NTP_SCALE_SHIFT;
> 	time_adjust = 0;
>+out:
>+	spin_unlock_irqrestore(&ntp_lock, flags);
> }
> 
> #ifdef CONFIG_GENERIC_CMOS_UPDATE
>@@ -476,7 +495,7 @@ int do_adjtimex(struct timex *txc)
> 
> 	getnstimeofday(&ts);
> 
>-	write_seqlock_irq(&xtime_lock);
>+	spin_lock_irq(&ntp_lock);
> 
> 	if (txc->modes & ADJ_ADJTIME) {
> 		long save_adjust = time_adjust;
>@@ -524,7 +543,7 @@ int do_adjtimex(struct timex *txc)
> 	txc->errcnt	   = 0;
> 	txc->stbcnt	   = 0;
> 
>-	write_sequnlock_irq(&xtime_lock);
>+	spin_unlock_irq(&ntp_lock);
> 
> 	txc->time.tv_sec = ts.tv_sec;
> 	txc->time.tv_usec = ts.tv_nsec;
>diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
>index d18dc69..bae541b 100644
>--- a/kernel/time/timekeeping.c
>+++ b/kernel/time/timekeeping.c
>@@ -172,12 +172,14 @@ void update_xtime_cache(u64 nsec)
> 	timespec_add_ns(&xtime_cache, nsec);
> }
> 
>-/* must hold xtime_lock */
>+/* RHEL6: only called in softirq context from hrtimer expiration */
> void timekeeping_leap_insert(int leapsecond)
> {
>+	write_seqlock(&xtime_lock);
> 	xtime.tv_sec += leapsecond;
> 	wall_to_monotonic.tv_sec -= leapsecond;
> 	update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
>+	write_sequnlock(&xtime_lock);
> }
> 
> #ifdef CONFIG_GENERIC_TIME
>-- 
>1.7.9.3
>

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