2008-08-05 20:15:08

by Jeff Dike

[permalink] [raw]
Subject: [PATCH 2/14] uml: fix bad NTP interaction with clock

>From cfd28f6695d0fc047478480791a21bdd4967f98e

UML's supposed nanosecond clock interacts badly with NTP when NTP
decides that the clock has drifted ahead and needs to be slowed down.
Slowing down the clock is done by decrementing the cycle-to-nanosecond
multiplier, which is 1. Decrementing that gives you 0 and time is
stopped.

This is fixed by switching to a microsecond clock, with a multiplier
of 1000.

Signed-off-by: Jeff Dike <[email protected]>
Cc: WANG Cong <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
---
arch/um/kernel/time.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index e066e84..5036c81 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -74,7 +74,7 @@ static irqreturn_t um_timer(int irq, void *dev)

static cycle_t itimer_read(void)
{
- return os_nsecs();
+ return os_nsecs() / 1000;
}

static struct clocksource itimer_clocksource = {
@@ -82,7 +82,7 @@ static struct clocksource itimer_clocksource = {
.rating = 300,
.read = itimer_read,
.mask = CLOCKSOURCE_MASK(64),
- .mult = 1,
+ .mult = 1000,
.shift = 0,
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
--
1.5.5.1


2008-08-16 22:36:33

by Greg KH

[permalink] [raw]
Subject: patch uml-fix-bad-ntp-interaction-with-clock.patch added to 2.6.25-stable tree


This is a note to let you know that we have just queued up the patch titled

Subject: uml: fix bad NTP interaction with clock

to the 2.6.25-stable tree. Its filename is

uml-fix-bad-ntp-interaction-with-clock.patch

A git repo of this tree can be found at
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary


>From [email protected] Tue Aug 5 13:14:46 2008
From: Jeff Dike <[email protected]>
Date: Tue, 5 Aug 2008 16:14:03 -0400
Subject: uml: fix bad NTP interaction with clock
To: [email protected]
Cc: LKML <[email protected]>, uml-devel <[email protected]>
Message-ID: <[email protected]>
Content-Disposition: inline

From: Jeff Dike <[email protected]>

commit cfd28f6695d0fc047478480791a21bdd4967f98e upstream

UML's supposed nanosecond clock interacts badly with NTP when NTP
decides that the clock has drifted ahead and needs to be slowed down.
Slowing down the clock is done by decrementing the cycle-to-nanosecond
multiplier, which is 1. Decrementing that gives you 0 and time is
stopped.

This is fixed by switching to a microsecond clock, with a multiplier
of 1000.

Signed-off-by: Jeff Dike <[email protected]>
Cc: WANG Cong <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
arch/um/kernel/time.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -74,7 +74,7 @@ static irqreturn_t um_timer(int irq, voi

static cycle_t itimer_read(void)
{
- return os_nsecs();
+ return os_nsecs() / 1000;
}

static struct clocksource itimer_clocksource = {
@@ -82,7 +82,7 @@ static struct clocksource itimer_clockso
.rating = 300,
.read = itimer_read,
.mask = CLOCKSOURCE_MASK(64),
- .mult = 1,
+ .mult = 1000,
.shift = 0,
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};


Patches currently in stable-queue which might be from [email protected] are

queue-2.6.25/uml-fix-build-when-slob-is-enabled.patch
queue-2.6.25/uml-fix-bad-ntp-interaction-with-clock.patch
queue-2.6.25/uml-physical-memory-shouldn-t-include-initial-stack.patch
queue-2.6.25/uml-track-and-make-up-lost-ticks.patch
queue-2.6.25/uml-missed-kmalloc-in-pcap_user.c.patch
queue-2.6.25/uml-deal-with-host-time-going-backwards.patch
queue-2.6.25/uml-deal-with-inaccessible-address-space-start.patch
queue-2.6.25/uml-missing-export-of-csum_partial-on-uml-amd64.patch
queue-2.6.25/uml-memcpy-export-needs-to-follow-host-declaration.patch
queue-2.6.25/uml-stub-needs-to-tolerate-sigwinch.patch
queue-2.6.25/uml-work-around-broken-host-ptrace_sysemu.patch
queue-2.6.25/uml-fix-gcc-ices-and-unresolved-externs.patch
queue-2.6.25/uml-fix-boot-crash.patch