The x86 arch has shifted its use of the nmi_watchdog from a
local implementation to the global one provide by
kernel/watchdog.c.  This shift has caused a whole bunch of
compile problems under different config options.  I attempt to
simplify things with the patch below.

In order to simplify things, I had to come to terms with the
meaning of two terms ARCH_HAS_NMI_WATCHDOG and
CONFIG_HARDLOCKUP_DETECTOR.  Basically they mean the same thing,
the former on a local level and the latter on a global level.

With the old x86 nmi watchdog gone, there is no need to rely on
defining the ARCH_HAS_NMI_WATCHDOG variable because it doesn't
make sense any more.  x86 will now use the global
implementation.

The changes below do a few things.  First it changes the few
places that relied on ARCH_HAS_NMI_WATCHDOG to use
CONFIG_X86_LOCAL_APIC (the former was an alias for the latter
anyway, so nothing unusual here).  Those pieces of code were
relying more on local apic functionality the nmi watchdog
functionality, so the change should make sense.

Second, I removed the x86 implementation of
touch_nmi_watchdog().  It isn't need now, instead x86 will rely
on kernel/watchdog.c's implementation.

Third, I removed the #define ARCH_HAS_NMI_WATCHDOG itself from
x86.  And tweaked the include/linux/nmi.h file to tell users to
look for an externally defined touch_nmi_watchdog in the case of
ARCH_HAS_NMI_WATCHDOG _or_ CONFIG_HARDLOCKUP_DETECTOR. This
changes removes some of the ugliness in that file.

Finally, I added a Kconfig dependency for
CONFIG_HARDLOCKUP_DETECTOR that said you can't have
ARCH_HAS_NMI_WATCHDOG _and_ CONFIG_HARDLOCKUP_DETECTOR.  You can
only have one nmi_watchdog.

Tested with
ARCH=i386: allnoconfig, defconfig, allyesconfig, (various broken
configs) ARCH=x86_64: allnoconfig, defconfig, allyesconfig,
(various broken configs)

Hopefully, after this patch I won't get any more compile broken
emails. :-)

v3:
  changed a couple of 'linux/nmi.h' -> 'asm/nmi.h' to pick-up correct function
  prototypes when CONFIG_HARDLOCKUP_DETECTOR is not set.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: fweisbec@gmail.com
LKML-Reference: <1293044403-14117-1-git-send-email-dzickus@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

My patch that removed the old x86 nmi watchdog broke other
arches.  This change reverts a piece of that patch and puts the
change in the correct spot.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Reviewed-by: NCyrill Gorcunov <gorcunov@gmail.com>
Cc: fweisbec@gmail.com
Cc: yinghai@kernel.org
LKML-Reference: <1291068437-5331-2-git-send-email-dzickus@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Now that the bulk of the old nmi_watchdog is gone, remove all
the stub variables and hooks associated with it.

This touches lots of files mainly because of how the io_apic
nmi_watchdog was implemented.  Now that the io_apic nmi_watchdog
is forever gone, remove all its fingers.

Most of this code was not being exercised by virtue of
nmi_watchdog != NMI_IO_APIC, so there shouldn't be anything to
risky here.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Cc: fweisbec@gmail.com
Cc: gorcunov@openvz.org
LKML-Reference: <1289578944-28564-3-git-send-email-dzickus@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Now that we have a new nmi_watchdog that is more generic and
sits on top of the perf subsystem, we really do not need the old
nmi_watchdog any more.

In addition, the old nmi_watchdog doesn't really work if you are
using the default clocksource, hpet.  The old nmi_watchdog code
relied on local apic interrupts to determine if the cpu is still
alive.  With hpet as the clocksource, these interrupts don't
increment any more and the old nmi_watchdog triggers false
postives.

This piece removes the old nmi_watchdog code and stubs out any
variables and functions calls.  The stubs are the same ones used
by the new nmi_watchdog code, so it should be well tested.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Cc: fweisbec@gmail.com
Cc: gorcunov@openvz.org
LKML-Reference: <1289578944-28564-2-git-send-email-dzickus@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Combining the softlockup and hardlockup code causes watchdog.c
to build even without the hardlockup detection support.

So if an arch, that has the previous and the new nmi watchdog
implementations cohabiting, wants to know if the generic one
is in use, CONFIG_LOCKUP_DETECTOR is not a reliable check.
We need to use CONFIG_HARDLOCKUP_DETECTOR instead.

Fixes:
	kernel/built-in.o: In function `touch_nmi_watchdog':
	(.text+0x449bc): multiple definition of `touch_nmi_watchdog'
	arch/sparc/kernel/built-in.o:(.text+0x11b28): first defined here
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
LKML-Reference: <20100514151121.GR15159@redhat.com>
[ use CONFIG_HARDLOCKUP_DETECTOR instead of CONFIG_PERF_EVENTS_NMI]
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

The new nmi_watchdog (which uses the perf event subsystem) is very
similar in structure to the softlockup detector.  Using Ingo's
suggestion, I combined the two functionalities into one file:
kernel/watchdog.c.

Now both the nmi_watchdog (or hardlockup detector) and softlockup
detector sit on top of the perf event subsystem, which is run every
60 seconds or so to see if there are any lockups.

To detect hardlockups, cpus not responding to interrupts, I
implemented an hrtimer that runs 5 times for every perf event
overflow event.  If that stops counting on a cpu, then the cpu is
most likely in trouble.

To detect softlockups, tasks not yielding to the scheduler, I used the
previous kthread idea that now gets kicked every time the hrtimer fires.
If the kthread isn't being scheduled neither is anyone else and the
warning is printed to the console.

I tested this on x86_64 and both the softlockup and hardlockup paths
work.

V2:
- cleaned up the Kconfig and softlockup combination
- surrounded hardlockup cases with #ifdef CONFIG_PERF_EVENTS_NMI
- seperated out the softlockup case from perf event subsystem
- re-arranged the enabling/disabling nmi watchdog from proc space
- added cpumasks for hardlockup failure cases
- removed fallback to soft events if no PMU exists for hard events

V3:
- comment cleanups
- drop support for older softlockup code
- per_cpu cleanups
- completely remove software clock base hardlockup detector
- use per_cpu masking on hard/soft lockup detection
- #ifdef cleanups
- rename config option NMI_WATCHDOG to LOCKUP_DETECTOR
- documentation additions

V4:
- documentation fixes
- convert per_cpu to __get_cpu_var
- powerpc compile fixes

V5:
- split apart warn flags for hard and soft lockups

TODO:
- figure out how to make an arch-agnostic clock2cycles call
  (if possible) to feed into perf events as a sample period

[fweisbec: merged conflict patch]
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
LKML-Reference: <1273266711-18706-2-git-send-email-dzickus@redhat.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

Mostly copy/paste whitespace damage with a couple of nitpicks by
the checkpatch script. Fix the struct definition as requested by Ingo too.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Cc: peterz@infradead.org
Cc: gorcunov@gmail.com
Cc: aris@redhat.com
LKML-Reference: <1266880143-24943-1-git-send-email-dzickus@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
--
 arch/x86/kernel/apic/hw_nmi.c |   14 +++++------
 arch/x86/kernel/traps.c       |    6 ++--
 include/linux/nmi.h           |    2 -
 kernel/nmi_watchdog.c         |   51 ++++++++++++++++++++----------------------
 4 files changed, 36 insertions(+), 37 deletions(-)

The original patch was x86_64 centric.  Changed the code to make
it less so.

ested by building and running on a powerpc.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Cc: peterz@infradead.org
Cc: gorcunov@gmail.com
Cc: aris@redhat.com
LKML-Reference: <1266013161-31197-2-git-send-email-dzickus@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

These are the bits that enable the new nmi_watchdog and safely
isolate the old nmi_watchdog.  Only one or the other can run,
not both at the same time.
Signed-off-by: NDon Zickus <dzickus@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: gorcunov@gmail.com
Cc: aris@redhat.com
Cc: peterz@infradead.org
LKML-Reference: <1265424425-31562-4-git-send-email-dzickus@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

As Andrew noted, my previous patch ("debug lockups: Improve lockup
detection") broke/removed SysRq-L support from architecture that do
not provide a __trigger_all_cpu_backtrace implementation.

Restore a fallback path and clean up the SysRq-L machinery a bit:

 - Rename the arch method to arch_trigger_all_cpu_backtrace()

 - Simplify the define

 - Document the method a bit - in the hope of more architectures
   adding support for it.

[ The patch touches Sparc code for the rename. ]

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "David S. Miller" <davem@davemloft.net>
LKML-Reference: <20090802140809.7ec4bb6b.akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

During kernel bootup, a new T60 laptop (CoreDuo, 32-bit) hangs about
10%-20% of the time in acpi_init():

 Calling initcall 0xc055ce1a: topology_init+0x0/0x2f()
 Calling initcall 0xc055d75e: mtrr_init_finialize+0x0/0x2c()
 Calling initcall 0xc05664f3: param_sysfs_init+0x0/0x175()
 Calling initcall 0xc014cb65: pm_sysrq_init+0x0/0x17()
 Calling initcall 0xc0569f99: init_bio+0x0/0xf4()
 Calling initcall 0xc056b865: genhd_device_init+0x0/0x50()
 Calling initcall 0xc056c4bd: fbmem_init+0x0/0x87()
 Calling initcall 0xc056dd74: acpi_init+0x0/0x1ee()

It's a hard hang that not even an NMI could punch through!  Frustratingly,
adding printks or function tracing to the ACPI code made the hangs go away
...

After some time an additional detail emerged: disabling the NMI watchdog
made these occasional hangs go away.

So i spent the better part of today trying to debug this and trying out
various theories when i finally found the likely reason for the hang: if
acpi_ns_initialize_devices() executes an _INI AML method and an NMI
happens to hit that AML execution in the wrong moment, the machine would
hang.  (my theory is that this must be some sort of chipset setup method
doing stores to chipset mmio registers?)

Unfortunately given the characteristics of the hang it was sheer
impossible to figure out which of the numerous AML methods is impacted
by this problem.

As a workaround i wrote an interface to disable chipset-based NMIs while
executing _INI sections - and indeed this fixed the hang.  I did a
boot-loop of 100 separate reboots and none hung - while without the patch
it would hang every 5-10 attempts.  Out of caution i did not touch the
nmi_watchdog=2 case (it's not related to the chipset anyway and didnt
hang).

I implemented this for both x86_64 and i686, tested the i686 laptop both
with nmi_watchdog=1 [which triggered the hangs] and nmi_watchdog=2, and
tested an Athlon64 box with the 64-bit kernel as well. Everything builds
and works with the patch applied.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

When a spinlock lockup occurs, arrange for the NMI code to emit an all-cpu
backtrace, so we get to see which CPU is holding the lock, and where.

Cc: Andi Kleen <ak@muc.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NAndi Kleen <ak@suse.de>

touch_nmi_watchdog() calls touch_softlockup_watchdog() on both
architectures that implement it (i386 and x86_64).  On other architectures
it does nothing at all.  touch_nmi_watchdog() should imply
touch_softlockup_watchdog() on all architectures.  Suggested by Andi Kleen.

[heiko.carstens@de.ibm.com: s390 fix]
Signed-off-by: NMichal Schmidt <xschmi00@stud.feec.vutbr.cz>
Cc: Andi Kleen <ak@muc.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Cc: Michal Schmidt <xschmi00@stud.feec.vutbr.cz>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!