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Ingo Molnar 126e01bf92 softlockup: fix NOHZ wakeup 
David Miller reported:

|--------------->
the following commit:

| commit 27ec440779
| Author: Ingo Molnar <mingo@elte.hu>
| Date:   Thu Feb 28 21:00:21 2008 +0100
|
|     sched: make cpu_clock() globally synchronous
|
|     Alexey Zaytsev reported (and bisected) that the introduction of
|     cpu_clock() in printk made the timestamps jump back and forth.
|
|     Make cpu_clock() more reliable while still keeping it fast when it's
|     called frequently.
|
|     Signed-off-by: Ingo Molnar <mingo@elte.hu>

causes watchdog triggers when a cpu exits NOHZ state when it has been
there for >= the soft lockup threshold, for example here are some
messages from a 128 cpu Niagara2 box:

[  168.106406] BUG: soft lockup - CPU#11 stuck for 128s! [dd:3239]
[  168.989592] BUG: soft lockup - CPU#21 stuck for 86s! [swapper:0]
[  168.999587] BUG: soft lockup - CPU#29 stuck for 91s! [make:4511]
[  168.999615] BUG: soft lockup - CPU#2 stuck for 85s! [swapper:0]
[  169.020514] BUG: soft lockup - CPU#37 stuck for 91s! [swapper:0]
[  169.020514] BUG: soft lockup - CPU#45 stuck for 91s! [sh:4515]
[  169.020515] BUG: soft lockup - CPU#69 stuck for 92s! [swapper:0]
[  169.020515] BUG: soft lockup - CPU#77 stuck for 92s! [swapper:0]
[  169.020515] BUG: soft lockup - CPU#61 stuck for 92s! [swapper:0]
[  169.112554] BUG: soft lockup - CPU#85 stuck for 92s! [swapper:0]
[  169.112554] BUG: soft lockup - CPU#101 stuck for 92s! [swapper:0]
[  169.112554] BUG: soft lockup - CPU#109 stuck for 92s! [swapper:0]
[  169.112554] BUG: soft lockup - CPU#117 stuck for 92s! [swapper:0]
[  169.171483] BUG: soft lockup - CPU#40 stuck for 80s! [dd:3239]
[  169.331483] BUG: soft lockup - CPU#13 stuck for 86s! [swapper:0]
[  169.351500] BUG: soft lockup - CPU#43 stuck for 101s! [dd:3239]
[  169.531482] BUG: soft lockup - CPU#9 stuck for 129s! [mkdir:4565]
[  169.595754] BUG: soft lockup - CPU#20 stuck for 93s! [swapper:0]
[  169.626787] BUG: soft lockup - CPU#52 stuck for 93s! [swapper:0]
[  169.626787] BUG: soft lockup - CPU#84 stuck for 92s! [swapper:0]
[  169.636812] BUG: soft lockup - CPU#116 stuck for 94s! [swapper:0]

It's simple enough to trigger this by doing a 10 minute sleep after a
fresh bootup then starting a parallel kernel build.

I suspect this might be reintroducing a problem we've had and fixed
before, see the thread:

http://marc.info/?l=linux-kernel&m=119546414004065&w=2
<---------------|

touch the softlockup watchdog when exiting NOHZ state - we are
obviously not locked up.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
 		2008-04-25 00:25:08 +02:00
..
Kconfig
…
Makefile
…
clockevents.c time: fix typo in comments 2008-02-08 09:22:29 -08:00
clocksource.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-hrt 2008-04-18 08:37:41 -07:00
jiffies.c
…
ntp.c time: remove obsolete CLOCK_TICK_ADJUST 2008-03-09 08:42:57 +01:00
tick-broadcast.c clockevents: fix typo in tick-broadcast.c 2008-04-21 07:59:51 +02:00
tick-common.c [S390] genirq/clockevents: move irq affinity prototypes/inlines to interrupt.h 2008-04-17 07:47:05 +02:00
tick-internal.h
…
tick-oneshot.c [S390] genirq/clockevents: move irq affinity prototypes/inlines to interrupt.h 2008-04-17 07:47:05 +02:00
tick-sched.c softlockup: fix NOHZ wakeup 2008-04-25 00:25:08 +02:00
timekeeping.c x86: tsc prevent time going backwards 2008-04-19 19:19:55 +02:00
timer_list.c timer_list: print relative expiry time signed 2008-02-17 17:29:38 +01:00
timer_stats.c
…