linux.git/kernel/time, branch v2.6.21.7

NTP: remove clock_was_set() call to prevent deadlock

2007-08-04T16:10:26+00:00

The clock_was_set() call in seconds_overflow() which happens only when
leap seconds are inserted / deleted is wrong in two aspects:

1. it results in a call to on_each_cpu() with interrupts disabled
2. it is potential deadlock source vs. call_lock in smp_call_function()

The only possible side effect of the removal might be, that an absolute
CLOCK_REALTIME timer fires 1 second too late, in the rare case of leap
second deletion and an absolute CLOCK_REALTIME timer which expires in
the affected time frame. It will never fire too early.

This was probably observed by the reporter of a June 30th -> July 1st
hang: http://lkml.org/lkml/2007/7/3/

A similar problem was observed by Dave Jones, who provided a screen shot
with a lockdep back trace, which allowed to analyse the problem.

Signed-off-by: Thomas Gleixner 
Cc: john stultz 
Cc: Dave Jones 
Cc: Ingo Molnar 
Cc: Vincent Fortier 
Signed-off-by: Chris Wright 
Signed-off-by: Greg Kroah-Hartman

[PATCH] timer stats: speedups

2007-06-11T18:36:48+00:00

Make timer-stats have almost zero overhead when enabled in the config but
not used.  (this way distros can enable it more easily)

Also update the documentation about overhead of timer_stats - it was
written for the first version which had a global lock and a linear list
walk based lookup ;-)

Andrew says:
And this.  Not a bugfix, but trivial and obvious and apparently some
distros don't want to enable timer_stats because of the performance
issue, but powertop uses timer_stats.

Ingo replies:
seconded. I have tested this with and without CONFIG_TIMER_STATS, with
and without timer_stats collection activated.

Signed-off-by: Ingo Molnar 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Chris Wright 
Signed-off-by: Greg Kroah-Hartman

[PATCH] timer statistics: fix race

2007-06-11T18:36:48+00:00

Fix two races in the timer stats lookup code.  One by ensuring that the
initialization of a new entry is finished upon insertion of that entry.
The other by cleaning up the hash table when the entries array is cleared,
so that we don't have any "pre-inserted" entries.

Thanks to Eric Dumazet for reminding me of the memory barriers.

Signed-off-by: Bjorn Steinbrink 
Signed-off-by: Ian Kumlien 
Acked-by: Ingo Molnar 
Cc: Eric Dumazet 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Chris Wright 
Signed-off-by: Greg Kroah-Hartman

[PATCH] NOHZ: Rate limit the local softirq pending warning output

2007-06-11T18:36:44+00:00

The warning in the NOHZ code, which triggers when a CPU goes idle with
softirqs pending can fill up the logs quite quickly.  Rate limit the output
until we found the root cause of that problem.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Chris Wright 
Signed-off-by: Greg Kroah-Hartman

[PATCH] Ignore bogus ACPI info for offline CPUs

2007-06-11T18:36:43+00:00

Booting a SMP kernel with maxcpus=1 on a SMP system leads to a hard
hang, because ACPI ignores the maxcpus setting and sends timer broadcast
info for the offline CPUs. This results in a stuck for ever call to
smp_call_function_single() on an offline CPU.

Ignore the bogus information and print a kernel error to remind ACPI
folks to fix it.

Affects 2.6.21 / 2.6.22-rc

Signed-off-by: Thomas Gleixner 
Signed-off-by: Chris Wright 
Signed-off-by: Greg Kroah-Hartman

[PATCH] clocksource: fix resume logic

2007-05-23T21:32:48+00:00

We need to make sure that the clocksources are resumed, when timekeeping is
resumed.  The current resume logic does not guarantee this.

Add a resume function pointer to the clocksource struct, so clocksource
drivers which need to reinitialize the clocksource can provide a resume
function.

Add a resume function, which calls the maybe available clocksource resume
functions and resets the watchdog function, so a stable TSC can be used
accross suspend/resume.

Signed-off-by: Thomas Gleixner 
Cc: john stultz 
Cc: Andi Kleen 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Chris Wright

[PATCH] highres/dyntick: prevent xtime lock contention

2007-05-23T21:32:46+00:00

While the !highres/!dyntick code assigns the duty of the do_timer() call to
one specific CPU, this was dropped in the highres/dyntick part during
development.

Steven Rostedt discovered the xtime lock contention on highres/dyntick due
to several CPUs trying to update jiffies.

Add the single CPU assignement back.  In the dyntick case this needs to be
handled carefully, as the CPU which has the do_timer() duty must drop the
assignement and let it be grabbed by another CPU, which is active.
Otherwise the do_timer() calls would not happen during the long sleep.

Signed-off-by: Thomas Gleixner 
Acked-by: Ingo Molnar 
Cc: Steven Rostedt 
Acked-by: Mark Lord 
Signed-off-by: Andrew Morton 
Signed-off-by: Chris Wright

[PATCH] fix jiffies clocksource inittime

2007-04-05T04:12:47+00:00

In debugging a problem w/ the -rt tree, I noticed that on systems that mark
the tsc as unstable before it is registered, the TSC would still be
selected and used for a short period of time.  Digging in it looks to be a
result of the mix of the clocksource list changes and my clocksource
initialization changes.

With the -rt tree, using a bad TSC, even for a short period of time can
results in a hang at boot.  I was not able to reproduce this hang w/
mainline, but I'm not completely certain that someone won't trip on it.

This patch resolves the issue by initializing the jiffies clocksource
earlier so a bad TSC won't get selected just because nothing else is yet
registered.

Signed-off-by: John Stultz 
Acked-by: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Andi Kleen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] ntp: avoid time_offset overflows

2007-03-27T16:05:15+00:00

I've been seeing some odd NTP behavior recently on a few boxes and
finally narrowed it down to time_offset overflowing when converted to
SHIFT_UPDATE units (which was a side effect from my HZfreeNTP patch).

This patch converts time_offset from a long to a s64 which resolves the
issue.

[tglx@linutronix.de: signedness fixes]
Signed-off-by: John Stultz 
Cc: Roman Zippel 
Cc: john stultz 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] clockevents: remove bad designed sysfs support for now

2007-03-26T21:07:23+00:00

The current sysfs support of clockevents does not obey the "only one
value per file" rule.

The real fix is not 2.6.21 material. Therefor remove the sysfs support
for now.

Signed-off-by: Thomas Gleixner 
Acked-by: Ingo Molnar 
Acked-by: Greg Kroah-Hartman 
Signed-off-by: Linus Torvalds