linux.git/kernel/watchdog.c, branch v4.1-rc2

Merge branch 'akpm' (patches from Andrew)

2015-04-14T23:49:17+00:00

Merge first patchbomb from Andrew Morton:

 - arch/sh updates

 - ocfs2 updates

 - kernel/watchdog feature

 - about half of mm/

* emailed patches from Andrew Morton : (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
  ...

watchdog: introduce the hardlockup_detector_disable() function

2015-04-14T23:48:59+00:00

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 
Signed-off-by: Don Zickus 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

watchdog: clean up some function names and arguments

2015-04-14T23:48:59+00:00

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 
Signed-off-by: Don Zickus 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

watchdog: enable the new user interface of the watchdog mechanism

2015-04-14T23:48:59+00:00

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 
Signed-off-by: Don Zickus 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

watchdog: implement error handling for failure to set up hardware perf events

2015-04-14T23:48:59+00:00

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 
Signed-off-by: Don Zickus 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

watchdog: introduce separate handlers for parameters in /proc/sys/kernel

2015-04-14T23:48:59+00:00

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 
Signed-off-by: Don Zickus 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

watchdog: introduce proc_watchdog_common()

2015-04-14T23:48:59+00:00

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 
Signed-off-by: Don Zickus 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

watchdog: move definition of 'watchdog_proc_mutex' outside of proc_dowatchdog()

2015-04-14T23:48:58+00:00

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 
Signed-off-by: Don Zickus 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

watchdog: introduce the proc_watchdog_update() function

2015-04-14T23:48:58+00:00

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 
Signed-off-by: Don Zickus 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

watchdog: new definitions and variables, initialization

2015-04-14T23:48:58+00:00

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 
Signed-off-by: Don Zickus 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds