Commit Graph

169 Commits

Author SHA1 Message Date
Ulrich Obergfell 8614ddef82 kernel/watchdog.c: avoid races between /proc handlers and CPU hotplug
The handler functions for watchdog parameters in /proc/sys/kernel do not
protect themselves against races with CPU hotplug.  Hence, theoretically
it is possible that a new watchdog thread is started on a hotplugged CPU
while a parameter is being modified, and the thread could thus use a
parameter value that is 'in transition'.

For example, if 'watchdog_thresh' is being set to zero (note: this
disables the lockup detectors) the thread would erroneously use the value
zero as the sample period.

To avoid such races and to keep the /proc handler code consistent,
call
     {get|put}_online_cpus() in proc_watchdog_common()
     {get|put}_online_cpus() in proc_watchdog_thresh()
     {get|put}_online_cpus() in proc_watchdog_cpumask()

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Ulrich Obergfell ee89e71eb0 kernel/watchdog.c: avoid race between lockup detector suspend/resume and CPU hotplug
The lockup detector suspend/resume interface that was introduced by
commit 8c073d27d7 ("watchdog: introduce watchdog_suspend() and
watchdog_resume()") does not protect itself against races with CPU
hotplug.  Hence, theoretically it is possible that a new watchdog thread
is started on a hotplugged CPU while the lockup detector is suspended,
and the thread could thus interfere unexpectedly with the code that
requested to suspend the lockup detector.

Avoid the race by calling

  get_online_cpus() in lockup_detector_suspend()
  put_online_cpus() in lockup_detector_resume()

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Don Zickus ac1f591249 kernel/watchdog.c: add sysctl knob hardlockup_panic
The only way to enable a hardlockup to panic the machine is to set
'nmi_watchdog=panic' on the kernel command line.

This makes it awkward for end users and folks who want to run automate
tests (like myself).

Mimic the softlockup_panic knob and create a /proc/sys/kernel/hardlockup_panic
knob.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Jiri Kosina 55537871ef kernel/watchdog.c: perform all-CPU backtrace in case of hard lockup
In many cases of hardlockup reports, it's actually not possible to know
why it triggered, because the CPU that got stuck is usually waiting on a
resource (with IRQs disabled) in posession of some other CPU is holding.

IOW, we are often looking at the stacktrace of the victim and not the
actual offender.

Introduce sysctl / cmdline parameter that makes it possible to have
hardlockup detector perform all-CPU backtrace.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Ulrich Obergfell ee7fed5405 watchdog: do not unpark threads in watchdog_park_threads() on error
If kthread_park() returns an error, watchdog_park_threads() should not
blindly 'roll back' the already parked threads to the unparked state.
Instead leave it up to the callers to handle such errors appropriately in
their context.  For example, it is redundant to unpark the threads if the
lockup detectors will soon be disabled by the callers anyway.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Ulrich Obergfell c993590c6a watchdog: implement error handling in lockup_detector_suspend()
lockup_detector_suspend() now handles errors from watchdog_park_threads().

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Ulrich Obergfell b43cb43cb8 watchdog: implement error handling in update_watchdog_all_cpus() and callers
update_watchdog_all_cpus() now passes errors from watchdog_park_threads()
up to functions in the call chain.  This allows watchdog_enable_all_cpus()
and proc_watchdog_update() to handle such errors too.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Ulrich Obergfell 58cf690a09 watchdog: move watchdog_disable_all_cpus() outside of ifdef
Move watchdog_disable_all_cpus() outside of the ifdef so that it is
available if CONFIG_SYSCTL is not defined.  This is preparation for
"watchdog: implement error handling in update_watchdog_all_cpus() and
callers".

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Ulrich Obergfell d283c640ce watchdog: fix error handling in proc_watchdog_thresh()
The original watchdog_park_threads() function that was introduced by
commit 81a4beef91 ("watchdog: introduce watchdog_park_threads() and
watchdog_unpark_threads()") takes a very simple approach to handle
errors returned by kthread_park(): It attempts to roll back all watchdog
threads to the unparked state.  However, this may be undesired behaviour
from the perspective of the caller which may want to handle errors as
appropriate in its specific context.  Currently, there are two possible
call chains:

- watchdog suspend/resume interface

    lockup_detector_suspend
      watchdog_park_threads

- write to parameters in /proc/sys/kernel

    proc_watchdog_update
      watchdog_enable_all_cpus
        update_watchdog_all_cpus
          watchdog_park_threads

Instead of 'blindly' attempting to unpark the watchdog threads if a
kthread_park() call fails, the new approach is to disable the lockup
detectors in the above call chains.  Failure becomes visible to the user
as follows:

- error messages from lockup_detector_suspend()
                   or watchdog_enable_all_cpus()

- the state that can be read from /proc/sys/kernel/watchdog_enabled

- the 'write' system call in the latter call chain returns an error

I did not experience kthread_park() failures in practice, I used some
instrumentation to fake error returns from kthread_park() in order to test
the patches.

This patch (of 5):

Restore the previous value of watchdog_thresh _and_ sample_period if
proc_watchdog_update() returns an error.  The variables must be consistent
to avoid false positives of the lockup detectors.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Yaowei Bai 451637e454 kernel/watchdog.c: is_hardlockup can be boolean
Make is_hardlockup return bool to improve readability due to this
particular function only using either one or zero as its return value.

No functional change.

Signed-off-by: Yaowei Bai <bywxiaobai@163.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05 19:34:48 -08:00
Ulrich Obergfell ec6a90661a watchdog: rename watchdog_suspend() and watchdog_resume()
Rename watchdog_suspend() to lockup_detector_suspend() and
watchdog_resume() to lockup_detector_resume() to avoid confusion with the
watchdog subsystem and to be consistent with the existing name
lockup_detector_init().

Also provide comment blocks to explain the watchdog_running and
watchdog_suspended variables and their relationship.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Stephane Eranian <eranian@google.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 16:54:41 -07:00
Ulrich Obergfell 999bbe49ea watchdog: use suspend/resume interface in fixup_ht_bug()
Remove watchdog_nmi_disable_all() and watchdog_nmi_enable_all() since
these functions are no longer needed.  If a subsystem has a need to
deactivate the watchdog temporarily, it should utilize the
watchdog_suspend() and watchdog_resume() functions.

[akpm@linux-foundation.org: fix build with CONFIG_LOCKUP_DETECTOR=m]
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Stephane Eranian <eranian@google.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 16:54:41 -07:00
Ulrich Obergfell d4bdd0b21c watchdog: use park/unpark functions in update_watchdog_all_cpus()
Remove update_watchdog() and restart_watchdog_hrtimer() since these
functions are no longer needed.  Changes of parameters such as the sample
period are honored at the time when the watchdog threads are being
unparked.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Stephane Eranian <eranian@google.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 16:54:41 -07:00
Ulrich Obergfell 8c073d27d7 watchdog: introduce watchdog_suspend() and watchdog_resume()
This interface can be utilized to deactivate the hard and soft lockup
detector temporarily.  Callers are expected to minimize the duration of
deactivation.  Multiple deactivations are allowed to occur in parallel but
should be rare in practice.

[akpm@linux-foundation.org: remove unneeded static initialization]
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Stephane Eranian <eranian@google.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 16:54:41 -07:00
Ulrich Obergfell 81a4beef91 watchdog: introduce watchdog_park_threads() and watchdog_unpark_threads()
Originally watchdog_nmi_enable(cpu) and watchdog_nmi_disable(cpu) were
only called in watchdog thread context.  However, the following commits
utilize these functions outside of watchdog thread context too.

  commit 9809b18fcf
  Author: Michal Hocko <mhocko@suse.cz>
  Date:   Tue Sep 24 15:27:30 2013 -0700

      watchdog: update watchdog_thresh properly

  commit b3738d2932
  Author: Stephane Eranian <eranian@google.com>
  Date:   Mon Nov 17 20:07:03 2014 +0100

      watchdog: Add watchdog enable/disable all functions

Hence, it is now possible that these functions execute concurrently with
the same 'cpu' argument.  This concurrency is problematic because per-cpu
'watchdog_ev' can be accessed/modified without adequate synchronization.

The patch series aims to address the above problem.  However, instead of
introducing locks to protect per-cpu 'watchdog_ev' a different approach is
taken: Invoke these functions by parking and unparking the watchdog
threads (to ensure they are always called in watchdog thread context).

  static struct smp_hotplug_thread watchdog_threads = {
           ...
          .park   = watchdog_disable, // calls watchdog_nmi_disable()
          .unpark = watchdog_enable,  // calls watchdog_nmi_enable()
  };

Both previously mentioned commits call these functions in a similar way
and thus in principle contain some duplicate code.  The patch series also
avoids this duplication by providing a commonly usable mechanism.

- Patch 1/4 introduces the watchdog_{park|unpark}_threads functions that
  park/unpark all watchdog threads specified in 'watchdog_cpumask'. They
  are intended to be called inside of kernel/watchdog.c only.

- Patch 2/4 introduces the watchdog_{suspend|resume} functions which can
  be utilized by external callers to deactivate the hard and soft lockup
  detector temporarily.

- Patch 3/4 utilizes watchdog_{park|unpark}_threads to replace some code
  that was introduced by commit 9809b18fcf.

- Patch 4/4 utilizes watchdog_{suspend|resume} to replace some code that
  was introduced by commit b3738d2932.

A few corner cases should be mentioned here for completeness.

- kthread_park() of watchdog/N could hang if cpu N is already locked up.
  However, if watchdog is enabled the lockup will be detected anyway.

- kthread_unpark() of watchdog/N could hang if cpu N got locked up after
  kthread_park(). The occurrence of this scenario should be _very_ rare
  in practice, in particular because it is not expected that temporary
  deactivation will happen frequently, and if it happens at all it is
  expected that the duration of deactivation will be short.

This patch (of 4): introduce watchdog_park_threads() and watchdog_unpark_threads()

These functions are intended to be used only from inside kernel/watchdog.c
to park/unpark all watchdog threads that are specified in
watchdog_cpumask.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Stephane Eranian <eranian@google.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 16:54:41 -07:00
Guenter Roeck aacfbe6a97 kernel/watchdog: move NMI function header declarations from watchdog.h to nmi.h
The kernel's NMI watchdog has nothing to do with the watchdog subsystem.
Its header declarations should be in linux/nmi.h, not linux/watchdog.h.

The code provided two sets of dummy functions if HARDLOCKUP_DETECTOR is
not configured, one in the include file and one in kernel/watchdog.c.
Remove the dummy functions from kernel/watchdog.c and use those from the
include file.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 16:54:41 -07:00
Frederic Weisbecker 314b08ff52 watchdog: simplify housekeeping affinity with the appropriate mask
housekeeping_mask gathers all the CPUs that aren't part of the nohz_full
set.  This is exactly what we want the watchdog to be affine to without
the need to use complicated cpumask operations.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 16:54:41 -07:00
Frederic Weisbecker 230ec93909 smpboot: allow passing the cpumask on per-cpu thread registration
It makes the registration cheaper and simpler for the smpboot per-cpu
kthread users that don't need to always update the cpumask after threads
creation.

[sfr@canb.auug.org.au: fix for allow passing the cpumask on per-cpu thread registration]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 16:54:41 -07:00
Chris Metcalf fe4ba3c343 watchdog: add watchdog_cpumask sysctl to assist nohz
Change the default behavior of watchdog so it only runs on the
housekeeping cores when nohz_full is enabled at build and boot time.
Allow modifying the set of cores the watchdog is currently running on
with a new kernel.watchdog_cpumask sysctl.

In the current system, the watchdog subsystem runs a periodic timer that
schedules the watchdog kthread to run.  However, nohz_full cores are
designed to allow userspace application code running on those cores to
have 100% access to the CPU.  So the watchdog system prevents the
nohz_full application code from being able to run the way it wants to,
thus the motivation to suppress the watchdog on nohz_full cores, which
this patchset provides by default.

However, if we disable the watchdog globally, then the housekeeping
cores can't benefit from the watchdog functionality.  So we allow
disabling it only on some cores.  See Documentation/lockup-watchdogs.txt
for more information.

[jhubbard@nvidia.com: fix a watchdog crash in some configurations]
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-06-24 17:49:40 -07:00
Michal Hocko 1173ff09b9 watchdog: fix double lock in watchdog_nmi_enable_all
Commit ab992dc38f ("watchdog: Fix merge 'conflict'") has introduced an
obvious deadlock because of a typo.  watchdog_proc_mutex should be
unlocked on exit.

Thanks to Miroslav Benes who was staring at the code with me and noticed
this.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Duh-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-05-19 10:57:03 -07:00
Peter Zijlstra ab992dc38f watchdog: Fix merge 'conflict'
Two watchdog changes that came through different trees had a non
conflicting conflict, that is, one changed the semantics of a variable
but no actual code conflict happened. So the merge appeared fine, but
the resulting code did not behave as expected.

Commit 195daf665a ("watchdog: enable the new user interface of the
watchdog mechanism") changes the semantics of watchdog_user_enabled,
which thereafter is only used by the functions introduced by
b3738d2932 ("watchdog: Add watchdog enable/disable all functions").

There further appears to be a distinct lack of serialization between
setting and using watchdog_enabled, so perhaps we should wrap the
{en,dis}able_all() things in watchdog_proc_mutex.

This patch fixes a s2r failure reported by Michal; which I cannot
readily explain. But this does make the code internally consistent
again.

Reported-and-tested-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-05-18 10:08:29 -07:00
Linus Torvalds 1dcf58d6e6 Merge branch 'akpm' (patches from Andrew)
Merge first patchbomb from Andrew Morton:

 - arch/sh updates

 - ocfs2 updates

 - kernel/watchdog feature

 - about half of mm/

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (122 commits)
  Documentation: update arch list in the 'memtest' entry
  Kconfig: memtest: update number of test patterns up to 17
  arm: add support for memtest
  arm64: add support for memtest
  memtest: use phys_addr_t for physical addresses
  mm: move memtest under mm
  mm, hugetlb: abort __get_user_pages if current has been oom killed
  mm, mempool: do not allow atomic resizing
  memcg: print cgroup information when system panics due to panic_on_oom
  mm: numa: remove migrate_ratelimited
  mm: fold arch_randomize_brk into ARCH_HAS_ELF_RANDOMIZE
  mm: split ET_DYN ASLR from mmap ASLR
  s390: redefine randomize_et_dyn for ELF_ET_DYN_BASE
  mm: expose arch_mmap_rnd when available
  s390: standardize mmap_rnd() usage
  powerpc: standardize mmap_rnd() usage
  mips: extract logic for mmap_rnd()
  arm64: standardize mmap_rnd() usage
  x86: standardize mmap_rnd() usage
  arm: factor out mmap ASLR into mmap_rnd
  ...
2015-04-14 16:49:17 -07:00
Ulrich Obergfell 692297d8f9 watchdog: introduce the hardlockup_detector_disable() function
Have kvm_guest_init() use hardlockup_detector_disable() instead of
watchdog_enable_hardlockup_detector(false).

Remove the watchdog_hardlockup_detector_is_enabled() and the
watchdog_enable_hardlockup_detector() function which are no longer needed.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 16:48:59 -07:00
Ulrich Obergfell b2f57c3a0d watchdog: clean up some function names and arguments
Rename the update_timers*() functions to update_watchdog*().

Remove the boolean argument from watchdog_enable_all_cpus() because
update_watchdog_all_cpus() is now a generic function to change the run
state of the lockup detectors and to have the lockup detectors use a new
sample period.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 16:48:59 -07:00
Ulrich Obergfell 195daf665a watchdog: enable the new user interface of the watchdog mechanism
With the current user interface of the watchdog mechanism it is only
possible to disable or enable both lockup detectors at the same time.
This series introduces new kernel parameters and changes the semantics of
some existing kernel parameters, so that the hard lockup detector and the
soft lockup detector can be disabled or enabled individually.  With this
series applied, the user interface is as follows.

- parameters in /proc/sys/kernel

  . soft_watchdog
    This is a new parameter to control and examine the run state of
    the soft lockup detector.

  . nmi_watchdog
    The semantics of this parameter have changed. It can now be used
    to control and examine the run state of the hard lockup detector.

  . watchdog
    This parameter is still available to control the run state of both
    lockup detectors at the same time. If this parameter is examined,
    it shows the logical OR of soft_watchdog and nmi_watchdog.

  . watchdog_thresh
    The semantics of this parameter are not affected by the patch.

- kernel command line parameters

  . nosoftlockup
    The semantics of this parameter have changed. It can now be used
    to disable the soft lockup detector at boot time.

  . nmi_watchdog=0 or nmi_watchdog=1
    Disable or enable the hard lockup detector at boot time. The patch
    introduces '=1' as a new option.

  . nowatchdog
    The semantics of this parameter are not affected by the patch. It
    is still available to disable both lockup detectors at boot time.

Also, remove the proc_dowatchdog() function which is no longer needed.

[dzickus@redhat.com: wrote changelog]
[dzickus@redhat.com: update documentation for kernel params and sysctl]
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 16:48:59 -07:00
Ulrich Obergfell bcfba4f4bf watchdog: implement error handling for failure to set up hardware perf events
If watchdog_nmi_enable() fails to set up the hardware perf event of one
CPU, the entire hard lockup detector is deemed unreliable.  Hence, disable
the hard lockup detector and shut down the hardware perf events on all
CPUs.

[dzickus@redhat.com: update comments to explain some code]
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 16:48:59 -07:00
Ulrich Obergfell 83a80a3907 watchdog: introduce separate handlers for parameters in /proc/sys/kernel
Separate handlers for each watchdog parameter in /proc/sys/kernel replace
the proc_dowatchdog() function.  Three of those handlers merely call
proc_watchdog_common() with one different argument.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 16:48:59 -07:00
Ulrich Obergfell ef246a216b watchdog: introduce proc_watchdog_common()
Three of four handlers for the watchdog parameters in /proc/sys/kernel
essentially have to do the same thing.

  if the parameter is being read {
    return the state of the corresponding bit(s) in 'watchdog_enabled'
  } else {
    set/clear the state of the corresponding bit(s) in 'watchdog_enabled'
    update the run state of the lockup detector(s)
  }

Hence, introduce a common function that can be called by those handlers.
The callers pass a 'bit mask' to this function to indicate which bit(s)
should be set/cleared in 'watchdog_enabled'.

This function handles an uncommon race with watchdog_nmi_enable() where a
concurrent update of 'watchdog_enabled' is possible.  We use 'cmpxchg' to
detect the concurrency.  [This avoids introducing a new spinlock or a
mutex to synchronize updates of 'watchdog_enabled'.  Using the same lock
or mutex in watchdog thread context and in system call context needs to be
considered carefully because it can make the code prone to deadlock
situations in connection with parking/unparking the watchdog threads.]

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 16:48:59 -07:00
Ulrich Obergfell f54c2274f5 watchdog: move definition of 'watchdog_proc_mutex' outside of proc_dowatchdog()
This series removes proc_dowatchdog().  Since multiple new functions need
the 'watchdog_proc_mutex' to serialize access to the watchdog parameters
in /proc/sys/kernel, move the mutex outside of any function.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 16:48:58 -07:00
Ulrich Obergfell a0c9cbb93d watchdog: introduce the proc_watchdog_update() function
This series introduces a separate handler for each watchdog parameter in
/proc/sys/kernel.  The separate handlers need a common function that they
can call to update the run state of the lockup detectors, or to have the
lockup detectors use a new sample period.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 16:48:58 -07:00
Ulrich Obergfell 84d56e66b9 watchdog: new definitions and variables, initialization
The hardlockup and softockup had always been tied together.  Due to the
request of KVM folks, they had a need to have one enabled but not the
other.  Internally rework the code to split things apart more cleanly.

There is a bunch of churn here, but the end result should be code that
should be easier to maintain and fix without knowing the internals of what
is going on.

This patch (of 9):

Introduce new definitions and variables to separate the user interface in
/proc/sys/kernel from the internal run state of the lockup detectors.  The
internal run state is represented by two bits in a new variable that is
named 'watchdog_enabled'.  This helps simplify the code, for example:

- In order to check if any of the two lockup detectors is enabled,
  it is sufficient to check if 'watchdog_enabled' is not zero.

- In order to enable/disable one or both lockup detectors,
  it is sufficient to set/clear one or both bits in 'watchdog_enabled'.

- Concurrent updates of 'watchdog_enabled' need not be synchronized via
  a spinlock or a mutex. Updates can either be atomic or concurrency can
  be detected by using 'cmpxchg'.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 16:48:58 -07:00
Stephane Eranian b3738d2932 watchdog: Add watchdog enable/disable all functions
This patch adds two new functions to enable/disable
the watchdog across all CPUs.

This will be used by the HT PMU bug workaround code to
disable/enable the NMI watchdog across quirk enablement.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: bp@alien8.de
Cc: jolsa@redhat.com
Cc: kan.liang@intel.com
Cc: maria.n.dimakopoulou@gmail.com
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1416251225-17721-12-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-04-02 17:33:15 +02:00
Cyril Bur 545a2bf742 kernel/sched/clock.c: add another clock for use with the soft lockup watchdog
When the hypervisor pauses a virtualised kernel the kernel will observe a
jump in timebase, this can cause spurious messages from the softlockup
detector.

Whilst these messages are harmless, they are accompanied with a stack
trace which causes undue concern and more problematically the stack trace
in the guest has nothing to do with the observed problem and can only be
misleading.

Futhermore, on POWER8 this is completely avoidable with the introduction
of the Virtual Time Base (VTB) register.

This patch (of 2):

This permits the use of arch specific clocks for which virtualised kernels
can use their notion of 'running' time, not the elpased wall time which
will include host execution time.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Andrew Jones <drjones@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: chai wen <chaiw.fnst@cn.fujitsu.com>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Ben Zhang <benzh@chromium.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 18:54:13 -08:00
Linus Torvalds 0429fbc0bd Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
Pull percpu consistent-ops changes from Tejun Heo:
 "Way back, before the current percpu allocator was implemented, static
  and dynamic percpu memory areas were allocated and handled separately
  and had their own accessors.  The distinction has been gone for many
  years now; however, the now duplicate two sets of accessors remained
  with the pointer based ones - this_cpu_*() - evolving various other
  operations over time.  During the process, we also accumulated other
  inconsistent operations.

  This pull request contains Christoph's patches to clean up the
  duplicate accessor situation.  __get_cpu_var() uses are replaced with
  with this_cpu_ptr() and __this_cpu_ptr() with raw_cpu_ptr().

  Unfortunately, the former sometimes is tricky thanks to C being a bit
  messy with the distinction between lvalues and pointers, which led to
  a rather ugly solution for cpumask_var_t involving the introduction of
  this_cpu_cpumask_var_ptr().

  This converts most of the uses but not all.  Christoph will follow up
  with the remaining conversions in this merge window and hopefully
  remove the obsolete accessors"

* 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (38 commits)
  irqchip: Properly fetch the per cpu offset
  percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t -fix
  ia64: sn_nodepda cannot be assigned to after this_cpu conversion. Use __this_cpu_write.
  percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t
  Revert "powerpc: Replace __get_cpu_var uses"
  percpu: Remove __this_cpu_ptr
  clocksource: Replace __this_cpu_ptr with raw_cpu_ptr
  sparc: Replace __get_cpu_var uses
  avr32: Replace __get_cpu_var with __this_cpu_write
  blackfin: Replace __get_cpu_var uses
  tile: Use this_cpu_ptr() for hardware counters
  tile: Replace __get_cpu_var uses
  powerpc: Replace __get_cpu_var uses
  alpha: Replace __get_cpu_var
  ia64: Replace __get_cpu_var uses
  s390: cio driver &__get_cpu_var replacements
  s390: Replace __get_cpu_var uses
  mips: Replace __get_cpu_var uses
  MIPS: Replace __get_cpu_var uses in FPU emulator.
  arm: Replace __this_cpu_ptr with raw_cpu_ptr
  ...
2014-10-15 07:48:18 +02:00
Ulrich Obergfell 6e7458a6f0 kernel/watchdog.c: control hard lockup detection default
In some cases we don't want hard lockup detection enabled by default.
An example is when running as a guest.  Introduce

  watchdog_enable_hardlockup_detector(bool)

allowing those cases to disable hard lockup detection.  This must be
executed early by the boot processor from e.g.  smp_prepare_boot_cpu, in
order to allow kernel command line arguments to override it, as well as
to avoid hard lockup detection being enabled before we've had a chance
to indicate that it's unwanted.  In summary,

  initial boot:					default=enabled
  smp_prepare_boot_cpu
    watchdog_enable_hardlockup_detector(false):	default=disabled
  cmdline has 'nmi_watchdog=1':			default=enabled

The running kernel still has the ability to enable/disable at any time
with /proc/sys/kernel/nmi_watchdog us usual.  However even when the
default has been overridden /proc/sys/kernel/nmi_watchdog will initially
show '1'.  To truly turn it on one must disable/enable it, i.e.

  echo 0 > /proc/sys/kernel/nmi_watchdog
  echo 1 > /proc/sys/kernel/nmi_watchdog

This patch will be immediately useful for KVM with the next patch of this
series.  Other hypervisor guest types may find it useful as well.

[akpm@linux-foundation.org: fix build]
[dzickus@redhat.com: fix compile issues on sparc]
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-10-14 02:18:27 +02:00
Linus Torvalds 13ead805c5 Merge branch 'perf-watchdog-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull watchdog fixes from Ingo Molnar:
 "Two small watchdog subsystem fixes"

* 'perf-watchdog-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  watchdog: Fix print-once on enable
  watchdog: Remove unnecessary header files
2014-10-13 16:10:06 +02:00
chai wen b1a8de1f53 softlockup: make detector be aware of task switch of processes hogging cpu
For now, soft lockup detector warns once for each case of process
softlockup.  But the thread 'watchdog/n' may not always get the cpu at the
time slot between the task switch of two processes hogging that cpu to
reset soft_watchdog_warn.

An example would be two processes hogging the cpu.  Process A causes the
softlockup warning and is killed manually by a user.  Process B
immediately becomes the new process hogging the cpu preventing the
softlockup code from resetting the soft_watchdog_warn variable.

This case is a false negative of "warn only once for a process", as there
may be a different process that is going to hog the cpu.  Resolve this by
saving/checking the task pointer of the hogging process and use that to
reset soft_watchdog_warn too.

[dzickus@redhat.com: update comment]
Signed-off-by: chai wen <chaiw.fnst@cn.fujitsu.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-10-09 22:25:48 -04:00
Christoph Lameter f7f66b05aa watchdog: Replace __raw_get_cpu_var uses
Most of these are the uses of &__raw_get_cpu_var for address calculation.

touch_softlockup_watchdog_sync() uses __raw_get_cpu_var to write to
per cpu variables. Use __this_cpu_write instead.

Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: linux-watchdog@vger.kernel.org
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2014-08-26 13:45:46 -04:00
Ulrich Obergfell df57714959 watchdog: Fix print-once on enable
This patch avoids printing the message 'enabled on all CPUs,
...' multiple times. For example, the issue can occur in the
following scenario:

1) watchdog_nmi_enable() fails to enable PMU counters and sets
   cpu0_err.

2) 'echo [0|1] > /proc/sys/kernel/nmi_watchdog' is executed to
   disable and re-enable the watchdog mechanism 'on the fly'.

3) If watchdog_nmi_enable() succeeds to enable PMU counters,
   each CPU will print the message because step1 left behind a
   non-zero cpu0_err.

   if (!IS_ERR(event)) {
       if (cpu == 0 || cpu0_err)
           pr_info("enabled on all CPUs, ...")

The patch avoids this by clearing cpu0_err in watchdog_nmi_disable().

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1407768567-171794-4-git-send-email-dzickus@redhat.com
[ Applied small cleanups. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-08-18 11:17:46 +02:00
chai wen f530504a06 watchdog: Remove unnecessary header files
Signed-off-by: chai wen <chaiw.fnst@cn.fujitsu.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1407768567-171794-2-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-08-18 11:17:46 +02:00
Josh Hunt 69361eef90 panic: add TAINT_SOFTLOCKUP
This taint flag will be set if the system has ever entered a softlockup
state.  Similar to TAINT_WARN it is useful to know whether or not the
system has been in a softlockup state when debugging.

[akpm@linux-foundation.org: apply the taint before calling panic()]
Signed-off-by: Josh Hunt <johunt@akamai.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-08-08 15:57:24 -07:00
Fabian Frederick 656c3b79f7 kernel/watchdog.c: convert printk/pr_warning to pr_foo()
Replace some obsolete functions.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-08-06 18:01:13 -07:00
Aaron Tomlin ed235875e2 kernel/watchdog.c: print traces for all cpus on lockup detection
A 'softlockup' is defined as a bug that causes the kernel to loop in
kernel mode for more than a predefined period to time, without giving
other tasks a chance to run.

Currently, upon detection of this condition by the per-cpu watchdog
task, debug information (including a stack trace) is sent to the system
log.

On some occasions, we have observed that the "victim" rather than the
actual "culprit" (i.e.  the owner/holder of the contended resource) is
reported to the user.  Often this information has proven to be
insufficient to assist debugging efforts.

To avoid loss of useful debug information, for architectures which
support NMI, this patch makes it possible to improve soft lockup
reporting.  This is accomplished by issuing an NMI to each cpu to obtain
a stack trace.

If NMI is not supported we just revert back to the old method.  A sysctl
and boot-time parameter is available to toggle this feature.

[dzickus@redhat.com: add CONFIG_SMP in certain areas]
[akpm@linux-foundation.org: additional CONFIG_SMP=n optimisations]
[mq@suse.cz: fix warning]
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jan Moskyto Matejka <mq@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-23 16:47:44 -07:00
Don Zickus bde92cf455 kernel/watchdog.c: remove preemption restrictions when restarting lockup detector
Peter Wu noticed the following splat on his machine when updating
/proc/sys/kernel/watchdog_thresh:

  BUG: sleeping function called from invalid context at mm/slub.c:965
  in_atomic(): 1, irqs_disabled(): 0, pid: 1, name: init
  3 locks held by init/1:
   #0:  (sb_writers#3){.+.+.+}, at: [<ffffffff8117b663>] vfs_write+0x143/0x180
   #1:  (watchdog_proc_mutex){+.+.+.}, at: [<ffffffff810e02d3>] proc_dowatchdog+0x33/0x110
   #2:  (cpu_hotplug.lock){.+.+.+}, at: [<ffffffff810589c2>] get_online_cpus+0x32/0x80
  Preemption disabled at:[<ffffffff810e0384>] proc_dowatchdog+0xe4/0x110

  CPU: 0 PID: 1 Comm: init Not tainted 3.16.0-rc1-testing #34
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Call Trace:
    dump_stack+0x4e/0x7a
    __might_sleep+0x11d/0x190
    kmem_cache_alloc_trace+0x4e/0x1e0
    perf_event_alloc+0x55/0x440
    perf_event_create_kernel_counter+0x26/0xe0
    watchdog_nmi_enable+0x75/0x140
    update_timers_all_cpus+0x53/0xa0
    proc_dowatchdog+0xe4/0x110
    proc_sys_call_handler+0xb3/0xc0
    proc_sys_write+0x14/0x20
    vfs_write+0xad/0x180
    SyS_write+0x49/0xb0
    system_call_fastpath+0x16/0x1b
  NMI watchdog: disabled (cpu0): hardware events not enabled

What happened is after updating the watchdog_thresh, the lockup detector
is restarted to utilize the new value.  Part of this process involved
disabling preemption.  Once preemption was disabled, perf tried to
allocate a new event (as part of the restart).  This caused the above
BUG_ON as you can't sleep with preemption disabled.

The preemption restriction seemed agressive as we are not doing anything
on that particular cpu, but with all the online cpus (which are
protected by the get_online_cpus lock).  Remove the restriction and the
BUG_ON goes away.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reported-by: Peter Wu <peter@lekensteyn.nl>
Tested-by: Peter Wu <peter@lekensteyn.nl>
Acked-by: David Rientjes <rientjes@google.com>
Cc: <stable@vger.kernel.org>		[3.13+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-23 16:47:43 -07:00
Andrew Morton 7861144b8c kernel/watchdog.c:touch_softlockup_watchdog(): use raw_cpu_write()
Fix:

  BUG: using __this_cpu_write() in preemptible [00000000] code: systemd-udevd/497
  caller is __this_cpu_preempt_check+0x13/0x20
  CPU: 3 PID: 497 Comm: systemd-udevd Tainted: G        W     3.15.0-rc1 #9
  Hardware name: Hewlett-Packard HP EliteBook 8470p/179B, BIOS 68ICF Ver. F.02 04/27/2012
  Call Trace:
    check_preemption_disabled+0xe1/0xf0
    __this_cpu_preempt_check+0x13/0x20
    touch_nmi_watchdog+0x28/0x40

Reported-by: Luis Henriques <luis.henriques@canonical.com>
Tested-by: Luis Henriques <luis.henriques@canonical.com>
Cc: Eric Piel <eric.piel@tremplin-utc.net>
Cc: Robert Moore <robert.moore@intel.com>
Cc: Lv Zheng <lv.zheng@intel.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-18 16:40:08 -07:00
Ben Zhang 62572e29bc kernel/watchdog.c: touch_nmi_watchdog should only touch local cpu not every one
I ran into a scenario where while one cpu was stuck and should have
panic'd because of the NMI watchdog, it didn't.  The reason was another
cpu was spewing stack dumps on to the console.  Upon investigation, I
noticed that when writing to the console and also when dumping the
stack, the watchdog is touched.

This causes all the cpus to reset their NMI watchdog flags and the
'stuck' cpu just spins forever.

This change causes the semantics of touch_nmi_watchdog to be changed
slightly.  Previously, I accidentally changed the semantics and we
noticed there was a codepath in which touch_nmi_watchdog could be
touched from a preemtible area.  That caused a BUG() to happen when
CONFIG_DEBUG_PREEMPT was enabled.  I believe it was the acpi code.

My attempt here re-introduces the change to have the
touch_nmi_watchdog() code only touch the local cpu instead of all of the
cpus.  But instead of using __get_cpu_var(), I use the
__raw_get_cpu_var() version.

This avoids the preemption problem.  However my reasoning wasn't because
I was trying to be lazy.  Instead I rationalized it as, well if
preemption is enabled then interrupts should be enabled to and the NMI
watchdog will have no reason to trigger.  So it won't matter if the
wrong cpu is touched because the percpu interrupt counters the NMI
watchdog uses should still be incrementing.

Don said:

: I'm ok with this patch, though it does alter the behaviour of how
: touch_nmi_watchdog works.  For the most part I don't think most callers
: need to touch all of the watchdogs (on each cpu).  Perhaps a corner case
: will pop up (the scheduler??  to mimic touch_all_softlockup_watchdogs() ).
:
: But this does address an issue where if a system is locked up and one cpu
: is spewing out useful debug messages (or error messages), the hard lockup
: will fail to go off.  We have seen this on RHEL also.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Ben Zhang <benzh@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-03 16:20:58 -07:00
Frederic Weisbecker e0a23b0628 watchdog: Simplify a little the IPI call
In order to remotely restart the watchdog hrtimer, update_timers()
allocates a csd on the stack and pass it to __smp_call_function_single().

There is no partcular need, however, for a specific csd here. Lets
simplify that a little by calling smp_call_function_single()
which can already take care of the csd allocation by itself.

Acked-by: Don Zickus <dzickus@redhat.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@fb.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2014-02-24 14:47:05 -08:00
Michal Hocko 9809b18fcf watchdog: update watchdog_thresh properly
watchdog_tresh controls how often nmi perf event counter checks per-cpu
hrtimer_interrupts counter and blows up if the counter hasn't changed
since the last check.  The counter is updated by per-cpu
watchdog_hrtimer hrtimer which is scheduled with 2/5 watchdog_thresh
period which guarantees that hrtimer is scheduled 2 times per the main
period.  Both hrtimer and perf event are started together when the
watchdog is enabled.

So far so good.  But...

But what happens when watchdog_thresh is updated from sysctl handler?

proc_dowatchdog will set a new sampling period and hrtimer callback
(watchdog_timer_fn) will use the new value in the next round.  The
problem, however, is that nobody tells the perf event that the sampling
period has changed so it is ticking with the period configured when it
has been set up.

This might result in an ear ripping dissonance between perf and hrtimer
parts if the watchdog_thresh is increased.  And even worse it might lead
to KABOOM if the watchdog is configured to panic on such a spurious
lockup.

This patch fixes the issue by updating both nmi perf even counter and
hrtimers if the threshold value has changed.

The nmi one is disabled and then reinitialized from scratch.  This has
an unpleasant side effect that the allocation of the new event might
fail theoretically so the hard lockup detector would be disabled for
such cpus.  On the other hand such a memory allocation failure is very
unlikely because the original event is deallocated right before.

It would be much nicer if we just changed perf event period but there
doesn't seem to be any API to do that right now.  It is also unfortunate
that perf_event_alloc uses GFP_KERNEL allocation unconditionally so we
cannot use on_each_cpu() and do the same thing from the per-cpu context.
The update from the current CPU should be safe because
perf_event_disable removes the event atomically before it clears the
per-cpu watchdog_ev so it cannot change anything under running handler
feet.

The hrtimer is simply restarted (thanks to Don Zickus who has pointed
this out) if it is queued because we cannot rely it will fire&adopt to
the new sampling period before a new nmi event triggers (when the
treshold is decreased).

[akpm@linux-foundation.org: the UP version of __smp_call_function_single ended up in the wrong place]
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-24 17:00:25 -07:00
Michal Hocko 359e6fab66 watchdog: update watchdog attributes atomically
proc_dowatchdog doesn't synchronize multiple callers which might lead to
confusion when two parallel callers might confuse watchdog_enable_all_cpus
resp watchdog_disable_all_cpus (eg watchdog gets enabled even if
watchdog_thresh was set to 0 already).

This patch adds a local mutex which synchronizes callers to the sysctl
handler.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-24 17:00:25 -07:00
Frederic Weisbecker 93786a5f6a watchdog: Make it work under full dynticks
A perf event can be used without forcing the tick to
stay alive if it doesn't use a frequency but a sample
period and if it doesn't throttle (raise storm of events).

Since the lockup detector neither use a perf event frequency
nor should ever throttle due to its high period, it can now
run concurrently with the full dynticks feature.

So remove the hack that disabled the watchdog.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Anish Singh <anish198519851985@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1374539466-4799-9-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-07-30 22:29:15 +02:00
Frederic Weisbecker 940be35ac0 watchdog: Boot-disable by default on full dynticks
When the watchdog runs, it prevents the full dynticks
CPUs from stopping their tick because the hard lockup
detector uses perf events internally, which in turn
rely on the periodic tick.

Since this is a rather confusing behaviour that is not
easy to track down and identify for those who want to
test CONFIG_NO_HZ_FULL, let's default disable the
watchdog on boot time when full dynticks is enabled.

The user can still enable it later on runtime using
proc or sysctl.

Reported-by: Steven Rostedt <rostedt@goodmis.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Anish Singh <anish198519851985@gmail.com>
2013-06-20 15:46:32 +02:00
Frederic Weisbecker 3c00ea82c7 watchdog: Rename confusing state variable
We have two very conflicting state variable names in the
watchdog:

* watchdog_enabled: This one reflects the user interface. It's
set to 1 by default and can be overriden with boot options
or sysctl/procfs interface.

* watchdog_disabled: This is the internal toggle state that
tells if watchdog threads, timers and NMI events are currently
running or not. This state mostly depends on the user settings.
It's a convenient state latch.

Now we really need to find clearer names because those
are just too confusing to encourage deep review.

watchdog_enabled now becomes watchdog_user_enabled to reflect
its purpose as an interface.

watchdog_disabled becomes watchdog_running to suggest its
role as a pure internal state.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Anish Singh <anish198519851985@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Don Zickus <dzickus@redhat.com>
2013-06-20 15:41:18 +02:00
Frederic Weisbecker b8900bc021 watchdog: Register / unregister watchdog kthreads on sysctl control
The user activation/deactivation of the watchdog through boot parameters
or systcl is currently implemented with a dance involving kthreads parking
and unparking methods: the threads are unconditionally registered on
boot and they park as soon as the user want the watchdog to be disabled.

This method involves a few noisy details to handle though: the watchdog
kthreads may be unparked anytime due to hotplug operations, after which
the watchdog internals have to decide to park again if it is user-disabled.

As a result the setup() and unpark() methods need to be able to request a
reparking. This is not currently supported in the kthread infrastructure
so this piece of the watchdog code only works halfway.

Besides, unparking/reparking the watchdog kthreads consume unnecessary
cputime on hotplug operations when those could be simply ignored in the
first place.

As suggested by Srivatsa, let's instead only register the watchdog
threads when they are needed. This way we don't need to think about
hotplug operations and we don't burden the CPU onlining when the watchdog
is simply disabled.

Suggested-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Anish Singh <anish198519851985@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Don Zickus <dzickus@redhat.com>
2013-06-20 01:16:09 +02:00
anish kumar b66a2356d7 watchdog: Add comments to explain the watchdog_disabled variable
The watchdog_disabled flag is a bit cryptic. However it's
usefulness is multifold. Uses are:

 1. Check if smpboot_register_percpu_thread function passed.

 2. Makes sure that user enables and disables the watchdog in
    sequence i.e. enable watchdog->disable watchdog->enable watchdog
    Unlike enable watchdog->enable watchdog which is wrong.

Signed-off-by: anish kumar <anish198519851985@gmail.com>
[small text cleanups]
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: chuansheng.liu@intel.com
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1363113848-18344-1-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-03-14 08:24:05 +01:00
Linus Torvalds 3b5d8510b9 Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core locking changes from Ingo Molnar:
 "The biggest change is the rwsem lock-steal improvements, both to the
  assembly optimized and the spinlock based variants.

  The other notable change is the clean up of the seqlock implementation
  to be based on the seqcount infrastructure.

  The rest is assorted smaller debuggability, cleanup and continued -rt
  locking changes."

* 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rwsem-spinlock: Implement writer lock-stealing for better scalability
  futex: Revert "futex: Mark get_robust_list as deprecated"
  generic: Use raw local irq variant for generic cmpxchg
  lockdep: Selftest: convert spinlock to raw spinlock
  seqlock: Use seqcount infrastructure
  seqlock: Remove unused functions
  ntp: Make ntp_lock raw
  intel_idle: Convert i7300_idle_lock to raw_spinlock
  locking: Various static lock initializer fixes
  lockdep: Print more info when MAX_LOCK_DEPTH is exceeded
  rwsem: Implement writer lock-stealing for better scalability
  lockdep: Silence warning if CONFIG_LOCKDEP isn't set
  watchdog: Use local_clock for get_timestamp()
  lockdep: Rename print_unlock_inbalance_bug() to print_unlock_imbalance_bug()
  locking/stat: Fix a typo
2013-02-22 19:25:09 -08:00
Namhyung Kim c06b4f1947 watchdog: Use local_clock for get_timestamp()
The get_timestamp() function is always called with current cpu,
thus using local_clock() would be more appropriate and it makes
the code shorter and cleaner IMHO.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1356576585-28782-1-git-send-email-namhyung@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-02-19 08:42:40 +01:00
Clark Williams 8bd75c77b7 sched/rt: Move rt specific bits into new header file
Move rt scheduler definitions out of include/linux/sched.h into
new file include/linux/sched/rt.h

Signed-off-by: Clark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20130207094707.7b9f825f@riff.lan
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-02-07 20:51:08 +01:00
Bjørn Mork 3935e89505 watchdog: Fix disable/enable regression
Commit 8d4516904b ("watchdog: Fix CPU hotplug regression") causes an
oops or hard lockup when doing

 echo 0 > /proc/sys/kernel/nmi_watchdog
 echo 1 > /proc/sys/kernel/nmi_watchdog

and the kernel is booted with nmi_watchdog=1 (default)

Running laptop-mode-tools and disconnecting/connecting AC power will
cause this to trigger, making it a common failure scenario on laptops.

Instead of bailing out of watchdog_disable() when !watchdog_enabled we
can initialize the hrtimer regardless of watchdog_enabled status.  This
makes it safe to call watchdog_disable() in the nmi_watchdog=0 case,
without the negative effect on the enabled => disabled => enabled case.

All these tests pass with this patch:
- nmi_watchdog=1
  echo 0 > /proc/sys/kernel/nmi_watchdog
  echo 1 > /proc/sys/kernel/nmi_watchdog

- nmi_watchdog=0
  echo 0 > /sys/devices/system/cpu/cpu1/online

- nmi_watchdog=0
  echo mem > /sys/power/state

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=51661

Cc: <stable@vger.kernel.org> # v3.7
Cc: Norbert Warmuth <nwarmuth@t-online.de>
Cc: Joseph Salisbury <joseph.salisbury@canonical.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-19 12:10:33 -08:00
Chuansheng Liu 0f34c40091 watchdog: store the watchdog sample period as a variable
Currently getting the sample period is always thru a complex
calculation: get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5).

We can store the sample period as a variable, and set it as __read_mostly
type.

Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
Cc: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-17 17:15:13 -08:00
Thomas Gleixner 8d4516904b watchdog: Fix CPU hotplug regression
Norbert reported:
"3.7-rc6 booted with nmi_watchdog=0 fails to suspend to RAM or
 offline CPUs. It's reproducable with a KVM guest and physical
 system."

The reason is that commit bcd951cf(watchdog: Use hotplug thread
infrastructure) missed to take this into account. So the cpu offline
code gets stuck in the teardown function because it accesses non
initialized data structures.

Add a check for watchdog_enabled into that path to cure the issue.

Reported-and-tested-by: Norbert Warmuth <nwarmuth@t-online.de>
Tested-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1211231033230.2701@ionos
Link: http://bugs.launchpad.net/bugs/1079534
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-12-04 19:56:59 +01:00
Chuansheng Liu 8ffeb9b0e6 watchdog: using u64 in get_sample_period()
In get_sample_period(), unsigned long is not enough:

  watchdog_thresh * 2 * (NSEC_PER_SEC / 5)

case1:
  watchdog_thresh is 10 by default, the sample value will be: 0xEE6B2800

case2:
 set watchdog_thresh is 20, the sample value will be: 0x1 DCD6 5000

In case2, we need use u64 to express the sample period.  Otherwise,
changing the threshold thru proc often can not be successful.

Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-11-26 17:41:24 -08:00
Thomas Gleixner bcd951cf10 watchdog: Use hotplug thread infrastructure
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20120716103948.563736676@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 17:01:07 +02:00
Rafael J. Wysocki 300d3739e8 Revert "NMI watchdog: fix for lockup detector breakage on resume"
Revert commit 45226e9 (NMI watchdog: fix for lockup detector breakage
on resume) which breaks resume from system suspend on my SH7372
Mackerel board (by causing a NULL pointer dereference to happen) and
is generally wrong, because it abuses the CPU hotplug functionality
in a shamelessly blatant way.

The original issue should be addressed through appropriate syscore
resume callback instead.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2012-08-08 20:49:45 +02:00
Sameer Nanda 45226e944c NMI watchdog: fix for lockup detector breakage on resume
On the suspend/resume path the boot CPU does not go though an
offline->online transition.  This breaks the NMI detector post-resume
since it depends on PMU state that is lost when the system gets
suspended.

Fix this by forcing a CPU offline->online transition for the lockup
detector on the boot CPU during resume.

To provide more context, we enable NMI watchdog on Chrome OS.  We have
seen several reports of systems freezing up completely which indicated
that the NMI watchdog was not firing for some reason.

Debugging further, we found a simple way of repro'ing system freezes --
issuing the command 'tasket 1 sh -c "echo nmilockup > /proc/breakme"'
after the system has been suspended/resumed one or more times.

With this patch in place, the system freeze result in panics, as
expected.

These panics provide a nice stack trace for us to debug the actual issue
causing the freeze.

[akpm@linux-foundation.org: fiddle with code comment]
[akpm@linux-foundation.org: make lockup_detector_bootcpu_resume() conditional on CONFIG_SUSPEND]
[akpm@linux-foundation.org: fix section errors]
Signed-off-by: Sameer Nanda <snanda@chromium.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Mandeep Singh Baines <msb@chromium.org>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-30 17:25:13 -07:00
Don Zickus a702704682 watchdog: Quiet down the boot messages
A bunch of bugzillas have complained how noisy the nmi_watchdog
is during boot-up especially with its expected failure cases
(like virt and bios resource contention).

This is my attempt to quiet them down and keep it less confusing
for the end user.  What I did is print the message for cpu0 and
save it for future comparisons.  If future cpus have an
identical message as cpu0, then don't print the redundant info.
However, if a future cpu has a different message, happily print
that loudly.

Before the change, you would see something like:

    ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
    CPU0: Intel(R) Core(TM)2 Quad CPU    Q9550  @ 2.83GHz stepping 0a
    Performance Events: PEBS fmt0+, Core2 events, Intel PMU driver.
    ... version:                2
    ... bit width:              40
    ... generic registers:      2
    ... value mask:             000000ffffffffff
    ... max period:             000000007fffffff
    ... fixed-purpose events:   3
    ... event mask:             0000000700000003
    NMI watchdog enabled, takes one hw-pmu counter.
    Booting Node   0, Processors  #1
    NMI watchdog enabled, takes one hw-pmu counter.
     #2
    NMI watchdog enabled, takes one hw-pmu counter.
     #3 Ok.
    NMI watchdog enabled, takes one hw-pmu counter.
    Brought up 4 CPUs
    Total of 4 processors activated (22607.24 BogoMIPS).

After the change, it is simplified to:

    ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
    CPU0: Intel(R) Core(TM)2 Quad CPU    Q9550  @ 2.83GHz stepping 0a
    Performance Events: PEBS fmt0+, Core2 events, Intel PMU driver.
    ... version:                2
    ... bit width:              40
    ... generic registers:      2
    ... value mask:             000000ffffffffff
    ... max period:             000000007fffffff
    ... fixed-purpose events:   3
    ... event mask:             0000000700000003
    NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter.
    Booting Node   0, Processors  #1 #2 #3 Ok.
    Brought up 4 CPUs

V2: little changes based on Joe Perches' feedback
V3: printk cleanup based on Ingo's feedback; checkpatch fix
V4: keep printk as one long line
V5: Ingo fix ups

Reported-and-tested-by: Nathan Zimmer <nzimmer@sgi.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: nzimmer@sgi.com
Cc: joe@perches.com
Link: http://lkml.kernel.org/r/1339594548-17227-1-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-06-14 12:20:50 +02:00
Eric B Munson 5d1c0f4a80 watchdog: add check for suspended vm in softlockup detector
A suspended VM can cause spurious soft lockup warnings.  To avoid these, the
watchdog now checks if the kernel knows it was stopped by the host and skips
the warning if so.  When the watchdog is reset successfully, clear the guest
paused flag.

Signed-off-by: Eric B Munson <emunson@mgebm.net>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2012-04-08 12:49:03 +03:00
Andrew Morton b60f796c4c kernel/watchdog.c: add comment to watchdog() exit path
Revelation from Peter.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@tglx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-23 16:58:32 -07:00
Andrew Morton 4501980aae kernel/watchdog.c: convert to pr_foo()
It fixes some 80-col wordwrappings and adds some consistency.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-23 16:58:32 -07:00
Michal Hocko 7a05c0f7bb watchdog: make sure the watchdog thread gets CPU on loaded system
If the system is loaded while hotplugging a CPU we might end up with a
bogus hardlockup detection.  This has been seen during LTP pounder test
executed in parallel with hotplug test.

The main problem is that enable_watchdog (called when CPU is brought up)
registers perf event which periodically checks per-cpu counter
(hrtimer_interrupts), updated from a hrtimer callback, but the hrtimer
is fired from the kernel thread.

This means that while we already do check for the hard lockup the kernel
thread might be sitting on the runqueue with zillions of tasks so there
is nobody to update the value we rely on and so we KABOOM.

Let's fix this by boosting the watchdog thread priority before we wake
it up rather than when it's already running.  This still doesn't handle
a case where we have the same amount of high prio FIFO tasks but that
doesn't seem to be common.  The current implementation doesn't handle
that case anyway so this is not worse at least.

Unfortunately, we cannot start perf counter from the watchdog thread
because we could miss a real lock up and also we cannot start the
hrtimer watchdog_enable because we there is no way (at least I don't
know any) to start a hrtimer from a different CPU.

[dzickus@redhat.com: fix compile issue with param]
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Mandeep Singh Baines <msb@chromium.org>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-23 16:58:32 -07:00
Fernando Luis Vázquez Cao 86f5e6a7b1 watchdog: Fix code/comments mismatches
Reflect the change in the soft and hard lockup thresholds and
their relation to the frequency of the hrtimer and NMI events in
the code comments. While at it, remove references to files that
do not exist anymore.

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/r/1328827342-6253-3-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-11 15:11:33 +01:00
Prarit Bhargava b0f4c4b32c bugs, x86: Fix printk levels for panic, softlockups and stack dumps
rsyslog will display KERN_EMERG messages on a connected
terminal.  However, these messages are useless/undecipherable
for a general user.

For example, after a softlockup we get:

 Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ...
 kernel:Stack:

 Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ...
 kernel:Call Trace:

 Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ...
 kernel:Code: ff ff a8 08 75 25 31 d2 48 8d 86 38 e0 ff ff 48 89
 d1 0f 01 c8 0f ae f0 48 8b 86 38 e0 ff ff a8 08 75 08 b1 01 4c 89 e0 0f 01 c9 <e8> ea 69 dd ff 4c 29 e8 48 89 c7 e8 0f bc da ff 49 89 c4 49 89

This happens because the printk levels for these messages are
incorrect. Only an informational message should be displayed on
a terminal.

I modified the printk levels for various messages in the kernel
and tested the output by using the drivers/misc/lkdtm.c kernel
modules (ie, softlockups, panics, hard lockups, etc.) and
confirmed that the console output was still the same and that
the output to the terminals was correct.

For example, in the case of a softlockup we now see the much
more informative:

 Message from syslogd@intel-s3e37-04 at Jan 25 10:18:06 ...
 BUG: soft lockup - CPU4 stuck for 60s!

instead of the above confusing messages.

AFAICT, the messages no longer have to be KERN_EMERG.  In the
most important case of a panic we set console_verbose().  As for
the other less severe cases the correct data is output to the
console and /var/log/messages.

Successfully tested by me using the drivers/misc/lkdtm.c module.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: dzickus@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1327586134-11926-1-git-send-email-prarit@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-01-26 21:28:45 +01:00
Vasily Averin 4ff819515b watchdog: move watchdog_*_all_cpus under CONFIG_SYSCTL
Fix compilation warnings for CONFIG_SYSCTL=n:

fixed compilation warnings in case of disabled CONFIG_SYSCTL
kernel/watchdog.c:483:13: warning: `watchdog_enable_all_cpus' defined but not used
kernel/watchdog.c:500:13: warning: `watchdog_disable_all_cpus' defined but not used

these functions are static and are used only in sysctl handler, so move
them inside #ifdef CONFIG_SYSCTL too

Signed-off-by: Vasily Averin <vvs@sw.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-10-31 17:30:53 -07:00
Thomas Gleixner cba9bd22a5 watchdog: Drop FIFO policy in exit path
When the watchdog thread exits it runs through the exit path with FIFO
priority. There is no point in doing so. Switch back to SCHED_NORMAL
before exiting.

Cc: Don Zickus <dzickus@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1109121337461.2723@ionos
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-09-18 14:34:07 +02:00
Eric Dumazet 18e5a45db3 watchdog: Make the kthreads NUMA affine
Watchdog kthreads can use kthread_create_on_node() to NUMA affine their
stack and task_struct.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1312394344-18815-1-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-08-14 11:53:06 +02:00
Cyrill Gorcunov f912987097 perf, x86: P4 PMU - Introduce event alias feature
Instead of hw_nmi_watchdog_set_attr() weak function
and appropriate x86_pmu::hw_watchdog_set_attr() call
we introduce even alias mechanism which allow us
to drop this routines completely and isolate quirks
of Netburst architecture inside P4 PMU code only.

The main idea remains the same though -- to allow
nmi-watchdog and perf top run simultaneously.

Note the aliasing mechanism applies to generic
PERF_COUNT_HW_CPU_CYCLES event only because arbitrary
event (say passed as RAW initially) might have some
additional bits set inside ESCR register changing
the behaviour of event and we can't guarantee anymore
that alias event will give the same result.

P.S. Thanks a huge to Don and Steven for for testing
     and early review.

Acked-by: Don Zickus <dzickus@redhat.com>
Tested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Ingo Molnar <mingo@elte.hu>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Stephane Eranian <eranian@google.com>
CC: Lin Ming <ming.m.lin@intel.com>
CC: Arnaldo Carvalho de Melo <acme@redhat.com>
CC: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20110708201712.GS23657@sun
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-07-14 17:25:04 -04:00
Avi Kivity 4dc0da8696 perf: Add context field to perf_event
The perf_event overflow handler does not receive any caller-derived
argument, so many callers need to resort to looking up the perf_event
in their local data structure.  This is ugly and doesn't scale if a
single callback services many perf_events.

Fix by adding a context parameter to perf_event_create_kernel_counter()
(and derived hardware breakpoints APIs) and storing it in the perf_event.
The field can be accessed from the callback as event->overflow_handler_context.
All callers are updated.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1309362157-6596-2-git-send-email-avi@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-07-01 11:06:38 +02:00
Peter Zijlstra a8b0ca17b8 perf: Remove the nmi parameter from the swevent and overflow interface
The nmi parameter indicated if we could do wakeups from the current
context, if not, we would set some state and self-IPI and let the
resulting interrupt do the wakeup.

For the various event classes:

  - hardware: nmi=0; PMI is in fact an NMI or we run irq_work_run from
    the PMI-tail (ARM etc.)
  - tracepoint: nmi=0; since tracepoint could be from NMI context.
  - software: nmi=[0,1]; some, like the schedule thing cannot
    perform wakeups, and hence need 0.

As one can see, there is very little nmi=1 usage, and the down-side of
not using it is that on some platforms some software events can have a
jiffy delay in wakeup (when arch_irq_work_raise isn't implemented).

The up-side however is that we can remove the nmi parameter and save a
bunch of conditionals in fast paths.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Michael Cree <mcree@orcon.net.nz>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Don Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/n/tip-agjev8eu666tvknpb3iaj0fg@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-07-01 11:06:35 +02:00
Cyrill Gorcunov 1880c4ae18 perf, x86: Add hw_watchdog_set_attr() in a sake of nmi-watchdog on P4
Due to restriction and specifics of Netburst PMU we need a separated
event for NMI watchdog. In particular every Netburst event
consumes not just a counter and a config register, but also an
additional ESCR register.

Since ESCR registers are grouped upon counters (i.e. if ESCR is occupied
for some event there is no room for another event to enter until its
released) we need to pick up the "least" used ESCR (or the most available
one) for nmi-watchdog purposes -- so MSR_P4_CRU_ESCR2/3 was chosen.

With this patch nmi-watchdog and perf top should be able to run simultaneously.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Lin Ming <ming.m.lin@intel.com>
CC: Arnaldo Carvalho de Melo <acme@redhat.com>
CC: Frederic Weisbecker <fweisbec@gmail.com>
Tested-and-reviewed-by: Don Zickus <dzickus@redhat.com>
Tested-and-reviewed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110623124918.GC13050@sun
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-07-01 11:06:34 +02:00
Ingo Molnar 6e9101aeec watchdog: Fix non-standard prototype of get_softlockup_thresh()
This build warning slipped through:

  kernel/watchdog.c:102: warning: function declaration isn't a prototype

As reported by Stephen Rothwell.

Also address an unused variable warning that GCC 4.6.0 reports:
we cannot do anything about failed watchdog ops during CPU hotplug
(it's not serious enough to return an error from the notifier),
so ignore them.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Mandeep Singh Baines <msb@chromium.org>
Cc: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20110524134129.8da27016.sfr@canb.auug.org.au
Signed-off-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20110517071642.GF22305@elte.hu>
2011-05-24 05:53:39 +02:00
Mandeep Singh Baines 4eec42f392 watchdog: Change the default timeout and configure nmi watchdog period based on watchdog_thresh
Before the conversion of the NMI watchdog to perf event, the
watchdog timeout was 5 seconds. Now it is 60 seconds. For my
particular application, netbooks, 5 seconds was a better
timeout. With a short timeout, we catch faults earlier and are
able to send back a panic. With a 60 second timeout, the user is
unlikely to wait and will instead hit the power button, causing
us to lose the panic info.

This change configures the NMI period to watchdog_thresh and
sets the softlockup_thresh to watchdog_thresh * 2. In addition,
watchdog_thresh was reduced to 10 seconds as suggested by Ingo
Molnar.

Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1306127423-3347-4-git-send-email-msb@chromium.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20110517071642.GF22305@elte.hu>
2011-05-23 11:58:59 +02:00
Mandeep Singh Baines 586692a5a5 watchdog: Disable watchdog when thresh is zero
This restores the previous behavior of softlock_thresh.

Currently, setting watchdog_thresh to zero causes the watchdog
kthreads to consume a lot of CPU.

In addition, the logic of proc_dowatchdog_thresh and
proc_dowatchdog_enabled has been factored into proc_dowatchdog.

Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1306127423-3347-3-git-send-email-msb@chromium.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20110517071018.GE22305@elte.hu>
2011-05-23 11:58:59 +02:00
Mandeep Singh Baines e04ab2bc41 watchdog: Only disable/enable watchdog if neccessary
Don't take any action on an unsuccessful write to /proc.

Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1306127423-3347-2-git-send-email-msb@chromium.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-23 11:58:58 +02:00
Mandeep Singh Baines 824c6b7f62 watchdog: Fix rounding bug in get_sample_period()
In get_sample_period(), softlockup_thresh is integer divided by
5 before the multiplication by NSEC_PER_SEC. This results in
softlockup_thresh being rounded down to the nearest integer
multiple of 5.

For example, a softlockup_thresh of 4 rounds down to 0.

Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1306127423-3347-1-git-send-email-msb@chromium.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-23 11:58:58 +02:00
Hillf Danton 1409f141ac kernel/watchdog.c: disable nmi perf event in the error path of enabling watchdog
In corner cases where softlockup watchdog is not setup successfully, the
relevant nmi perf event for hardlockup watchdog could be disabled, then
the status of the underlying hardware remains unchanged.

Also, if the kthread doesn't start then the hrtimer won't run and the
hardlockup detector will falsely fire.

Signed-off-by: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-04-28 11:28:21 -07:00
Don Zickus f99a99330f kernel/watchdog.c: always return NOTIFY_OK during cpu up/down events
This patch addresses a couple of problems.  One was the case when the
hardlockup failed to start, it also failed to start the softlockup.  There
were valid cases when the hardlockup shouldn't start and that shouldn't
block the softlockup (no lapic, bios controls perf counters).

The second problem was when the hardlockup failed to start on boxes (from
a no lapic or bios controlled perf counter case), it reported failure to
the cpu notifier chain.  This blocked the notifier from continuing to
start other more critical pieces of cpu bring-up (in our case based on a
2.6.32 fork, it was the mce).  As a result, during soft cpu online/offline
testing, the system would panic when a cpu was offlined because the cpu
notifier would succeed in processing a watchdog disable cpu event and
would panic in the mce case as a result of un-initialized variables from a
never executed cpu up event.

I realized the hardlockup/softlockup cases are really just debugging aids
and should never impede the progress of a cpu up/down event.  Therefore I
modified the code to always return NOTIFY_OK and instead rely on printks
to inform the user of problems.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:12 -07:00
Don Zickus fef2c9bc1b kernel/watchdog.c: allow hardlockup to panic by default
When a cpu is considered stuck, instead of limping along and just printing
a warning, it is sometimes preferred to just panic, let kdump capture the
vmcore and reboot.  This gets the machine back into a stable state quickly
while saving the info that got it into a stuck state to begin with.

Add a Kconfig option to allow users to set the hardlockup to panic
by default.  Also add in a 'nmi_watchdog=nopanic' to override this.

[akpm@linux-foundation.org: fix strncmp length]
Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:12 -07:00
Don Zickus 5651f7f47d watchdog, nmi: Lower the severity of error messages
During boot if the hardlockup detector fails to initialize, it
complains very loudly.  Some failures should be expected under
certain situations, ie no lapics, or resource in-use.  Tone
those error messages down a bit.  Keep the rest at a high level.

Reported-by: Paul Bolle <pebolle@tiscali.nl>
Tested-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1297278153-21111-1-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-02-10 13:21:59 +01:00
Marcin Slusarz 9ffdc6c37d watchdog: Don't change watchdog state on read of sysctl
Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
[ add {}'s to fix a warning ]
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: <stable@kernel.org>
LKML-Reference: <1296230433-6261-3-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-01-31 13:22:43 +01:00
Marcin Slusarz 397357666d watchdog: Fix sysctl consistency
If it was not possible to enable watchdog for any cpu, switch
watchdog_enabled back to 0, because it's visible via
kernel.watchdog sysctl.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: <stable@kernel.org>
LKML-Reference: <1296230433-6261-2-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-01-31 13:22:43 +01:00
Marcin Slusarz 4135038a58 watchdog: Fix broken nowatchdog logic
Passing nowatchdog to kernel disables 2 things: creation of
watchdog threads AND initialization of percpu watchdog_hrtimer.
As hrtimers are initialized only at boot it's not possible to
enable watchdog later - for me all watchdog threads started to
eat 100% of CPU time, but they could just crash.

Additionally, even if these threads would start properly,
watchdog_disable_all_cpus was guarded by no_watchdog check, so
you couldn't disable watchdog.

To fix this, remove no_watchdog variable and use already
existing watchdog_enabled variable.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
[ removed another no_watchdog instance ]
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: <stable@kernel.org>
LKML-Reference: <1296230433-6261-1-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-01-31 13:22:42 +01:00
Linus Torvalds 72eb6a7914 Merge branch 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
* 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (30 commits)
  gameport: use this_cpu_read instead of lookup
  x86: udelay: Use this_cpu_read to avoid address calculation
  x86: Use this_cpu_inc_return for nmi counter
  x86: Replace uses of current_cpu_data with this_cpu ops
  x86: Use this_cpu_ops to optimize code
  vmstat: User per cpu atomics to avoid interrupt disable / enable
  irq_work: Use per cpu atomics instead of regular atomics
  cpuops: Use cmpxchg for xchg to avoid lock semantics
  x86: this_cpu_cmpxchg and this_cpu_xchg operations
  percpu: Generic this_cpu_cmpxchg() and this_cpu_xchg support
  percpu,x86: relocate this_cpu_add_return() and friends
  connector: Use this_cpu operations
  xen: Use this_cpu_inc_return
  taskstats: Use this_cpu_ops
  random: Use this_cpu_inc_return
  fs: Use this_cpu_inc_return in buffer.c
  highmem: Use this_cpu_xx_return() operations
  vmstat: Use this_cpu_inc_return for vm statistics
  x86: Support for this_cpu_add, sub, dec, inc_return
  percpu: Generic support for this_cpu_add, sub, dec, inc_return
  ...

Fixed up conflicts: in arch/x86/kernel/{apic/nmi.c, apic/x2apic_uv_x.c, process.c}
as per Tejun.
2011-01-07 17:02:58 -08:00
Linus Torvalds 65b2074f84 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (30 commits)
  sched: Change wait_for_completion_*_timeout() to return a signed long
  sched, autogroup: Fix reference leak
  sched, autogroup: Fix potential access to freed memory
  sched: Remove redundant CONFIG_CGROUP_SCHED ifdef
  sched: Fix interactivity bug by charging unaccounted run-time on entity re-weight
  sched: Move periodic share updates to entity_tick()
  printk: Use this_cpu_{read|write} api on printk_pending
  sched: Make pushable_tasks CONFIG_SMP dependant
  sched: Add 'autogroup' scheduling feature: automated per session task groups
  sched: Fix unregister_fair_sched_group()
  sched: Remove unused argument dest_cpu to migrate_task()
  mutexes, sched: Introduce arch_mutex_cpu_relax()
  sched: Add some clock info to sched_debug
  cpu: Remove incorrect BUG_ON
  cpu: Remove unused variable
  sched: Fix UP build breakage
  sched: Make task dump print all 15 chars of proc comm
  sched: Update tg->shares after cpu.shares write
  sched: Allow update_cfs_load() to update global load
  sched: Implement demand based update_cfs_load()
  ...
2011-01-06 10:23:33 -08:00
Ingo Molnar aef1b9cef7 Merge commit 'v2.6.37' into perf/core
Merge reason: Add the final .37 tree.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-01-05 14:22:10 +01:00
Ingo Molnar 27066fd484 Merge commit 'v2.6.37' into sched/core
Merge reason: Merge the final .37 tree.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-01-05 14:14:46 +01:00
Ben Hutchings 551423748a watchdog: Improve initialisation error message and documentation
The error message 'NMI watchdog failed to create perf event...'
does not make it clear that this is a fatal error for the
watchdog.  It also currently prints the error value as a
pointer, rather than extracting the error code with PTR_ERR().
Fix that.

Add a note to the description of the 'nowatchdog' kernel
parameter to associate it with this message.

Reported-by: Cesare Leonardi <celeonar@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: 599368@bugs.debian.org
Cc: 608138@bugs.debian.org
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: <stable@kernel.org> # .37.x and later
LKML-Reference: <1294009362.3167.126.camel@localhost>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-01-03 05:25:52 +01:00
Christoph Lameter 909ea96468 core: Replace __get_cpu_var with __this_cpu_read if not used for an address.
__get_cpu_var() can be replaced with this_cpu_read and will then use a
single read instruction with implied address calculation to access the
correct per cpu instance.

However, the address of a per cpu variable passed to __this_cpu_read()
cannot be determined (since it's an implied address conversion through
segment prefixes).  Therefore apply this only to uses of __get_cpu_var
where the address of the variable is not used.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Hugh Dickins <hughd@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2010-12-17 15:07:19 +01:00
Don Zickus 5dc3055879 x86, NMI: Add back unknown_nmi_panic and nmi_watchdog sysctls
Originally adapted from Huang Ying's patch which moved the
unknown_nmi_panic to the traps.c file.  Because the old nmi
watchdog was deleted before this change happened, the
unknown_nmi_panic sysctl was lost.  This re-adds it.

Also, the nmi_watchdog sysctl was re-implemented and its
documentation updated accordingly.

Patch-inspired-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Cc: fweisbec@gmail.com
LKML-Reference: <1291068437-5331-3-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-12-10 00:01:06 +01:00
Peter Zijlstra 004417a6d4 perf, arch: Cleanup perf-pmu init vs lockup-detector
The perf hardware pmu got initialized at various points in the boot,
some before early_initcall() some after (notably arch_initcall).

The problem is that the NMI lockup detector is ran from early_initcall()
and expects the hardware pmu to be present.

Sanitize this by moving all architecture hardware pmu implementations to
initialize at early_initcall() and move the lockup detector to an explicit
initcall right after that.

Cc: paulus <paulus@samba.org>
Cc: davem <davem@davemloft.net>
Cc: Michael Cree <mcree@orcon.net.nz>
Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1290707759.2145.119.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-11-26 15:14:56 +01:00
Ingo Molnar 92fd4d4d67 Merge commit 'v2.6.37-rc2' into sched/core
Merge reason: Move to a .37-rc base.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-11-18 13:22:26 +01:00
David Daney 433039e97f watchdog: Fix section mismatch and potential undefined behavior.
Commit d9ca07a05c ("watchdog: Avoid kernel crash when disabling
watchdog") introduces a section mismatch.

Now that we reference no_watchdog from non-__init code it can no longer
be __initdata.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-11-05 17:45:35 -07:00