20 Nov, 2015
1 commit
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Emulate NMIs on systems where they are not available by using timer
interrupts on other cpus. Each cpu will use its softlockup hrtimer
to check that the next cpu is processing hrtimer interrupts by
verifying that a counter is increasing.This patch is useful on systems where the hardlockup detector is not
available due to a lack of NMIs, for example most ARM SoCs.
Without this patch any cpu stuck with interrupts disabled can
cause a hardware watchdog reset with no debugging information,
but with this patch the kernel can detect the lockup and panic,
which can result in useful debugging info.Change-Id: Ia5faf50243e19c1755201212e04c8892d929785a
Signed-off-by: Colin Cross
20 May, 2015
1 commit
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Commit ab992dc38f9a ("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
Duh-by: Peter Zijlstra
Signed-off-by: Linus Torvalds
19 May, 2015
1 commit
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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 195daf665a62 ("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
b3738d293233 ("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
Signed-off-by: Peter Zijlstra (Intel)
Signed-off-by: Linus Torvalds
15 Apr, 2015
10 commits
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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
... -
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 -
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 -
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 -
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 -
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 -
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 -
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 -
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 -
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
02 Apr, 2015
1 commit
-
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
Signed-off-by: Peter Zijlstra (Intel)
Cc: bp@alien8.de
Cc: jolsa@redhat.com
Cc: kan.liang@intel.com
Cc: maria.n.dimakopoulou@gmail.com
Cc: Frederic Weisbecker
Cc: Don Zickus
Cc: Andrew Morton
Link: http://lkml.kernel.org/r/1416251225-17721-12-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar
13 Feb, 2015
1 commit
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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
Cc: Michael Ellerman
Cc: Andrew Jones
Acked-by: Don Zickus
Cc: Ingo Molnar
Cc: Ulrich Obergfell
Cc: chai wen
Cc: Fabian Frederick
Cc: Aaron Tomlin
Cc: Ben Zhang
Cc: Martin Schwidefsky
Cc: John Stultz
Cc: Thomas Gleixner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
15 Oct, 2014
1 commit
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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
...
14 Oct, 2014
1 commit
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In some cases we don't want hard lockup detection enabled by default.
An example is when running as a guest. Introducewatchdog_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=enabledThe 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_watchdogThis 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
Signed-off-by: Andrew Jones
Signed-off-by: Don Zickus
Signed-off-by: Don Zickus
Cc: Stephen Rothwell
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
13 Oct, 2014
1 commit
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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
10 Oct, 2014
1 commit
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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
Signed-off-by: Don Zickus
Cc: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
27 Aug, 2014
1 commit
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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
Cc: linux-watchdog@vger.kernel.org
Signed-off-by: Christoph Lameter
Signed-off-by: Tejun Heo
18 Aug, 2014
2 commits
-
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
Signed-off-by: Andrew Jones
Signed-off-by: Don Zickus
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 -
Signed-off-by: chai wen
Signed-off-by: Don Zickus
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1407768567-171794-2-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar
09 Aug, 2014
1 commit
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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
Cc: Jason Baron
Cc: Randy Dunlap
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
07 Aug, 2014
1 commit
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Replace some obsolete functions.
Signed-off-by: Fabian Frederick
Cc: Frederic Weisbecker
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
24 Jun, 2014
2 commits
-
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
Signed-off-by: Don Zickus
Cc: David S. Miller
Cc: Mateusz Guzik
Cc: Oleg Nesterov
Signed-off-by: Jan Moskyto Matejka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
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: [] vfs_write+0x143/0x180
#1: (watchdog_proc_mutex){+.+.+.}, at: [] proc_dowatchdog+0x33/0x110
#2: (cpu_hotplug.lock){.+.+.+}, at: [] get_online_cpus+0x32/0x80
Preemption disabled at:[] proc_dowatchdog+0xe4/0x110CPU: 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 enabledWhat 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
Acked-by: Michal Hocko
Reported-by: Peter Wu
Tested-by: Peter Wu
Acked-by: David Rientjes
Cc: [3.13+]
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
19 Apr, 2014
1 commit
-
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+0x28/0x40Reported-by: Luis Henriques
Tested-by: Luis Henriques
Cc: Eric Piel
Cc: Robert Moore
Cc: Lv Zheng
Cc: "Rafael J. Wysocki"
Cc: Len Brown
Cc: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
04 Apr, 2014
1 commit
-
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
Signed-off-by: Ben Zhang
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
25 Feb, 2014
1 commit
-
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
Reviewed-by: Michal Hocko
Cc: Andrew Morton
Cc: Christoph Hellwig
Cc: Don Zickus
Cc: Ingo Molnar
Cc: Jan Kara
Cc: Jens Axboe
Cc: Michal Hocko
Cc: Srivatsa S. Bhat
Signed-off-by: Frederic Weisbecker
Signed-off-by: Jens Axboe
25 Sep, 2013
2 commits
-
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
Acked-by: Don Zickus
Cc: Frederic Weisbecker
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: Fabio Estevam
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
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
Cc: Frederic Weisbecker
Acked-by: Don Zickus
Cc: Thomas Gleixner
Cc: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
31 Jul, 2013
1 commit
-
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
Cc: Jiri Olsa
Cc: Namhyung Kim
Cc: Arnaldo Carvalho de Melo
Cc: Stephane Eranian
Cc: Don Zickus
Cc: Srivatsa S. Bhat
Cc: Anish Singh
Signed-off-by: Peter Zijlstra
Link: http://lkml.kernel.org/r/1374539466-4799-9-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar
20 Jun, 2013
3 commits
-
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
Suggested-by: Peter Zijlstra
Signed-off-by: Frederic Weisbecker
Cc: Steven Rostedt
Cc: Paul E. McKenney
Cc: Ingo Molnar
Cc: Andrew Morton
Cc: Thomas Gleixner
Cc: Peter Zijlstra
Cc: Li Zhong
Cc: Don Zickus
Cc: Srivatsa S. Bhat
Cc: Anish Singh -
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
Cc: Srivatsa S. Bhat
Cc: Anish Singh
Cc: Steven Rostedt
Cc: Paul E. McKenney
Cc: Ingo Molnar
Cc: Thomas Gleixner
Cc: Peter Zijlstra
Cc: Borislav Petkov
Cc: Li Zhong
Cc: Don Zickus -
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
Signed-off-by: Frederic Weisbecker
Cc: Srivatsa S. Bhat
Cc: Anish Singh
Cc: Steven Rostedt
Cc: Paul E. McKenney
Cc: Ingo Molnar
Cc: Thomas Gleixner
Cc: Peter Zijlstra
Cc: Borislav Petkov
Cc: Li Zhong
Cc: Don Zickus
14 Mar, 2013
1 commit
-
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
[small text cleanups]
Signed-off-by: Don Zickus
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
23 Feb, 2013
1 commit
-
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
19 Feb, 2013
1 commit
-
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
Acked-by: Don Zickus
Cc: Steven Rostedt
Link: http://lkml.kernel.org/r/1356576585-28782-1-git-send-email-namhyung@kernel.org
Signed-off-by: Ingo Molnar
08 Feb, 2013
1 commit
-
Move rt scheduler definitions out of include/linux/sched.h into
new file include/linux/sched/rt.hSigned-off-by: Clark Williams
Cc: Peter Zijlstra
Cc: Steven Rostedt
Link: http://lkml.kernel.org/r/20130207094707.7b9f825f@riff.lan
Signed-off-by: Ingo Molnar
20 Dec, 2012
1 commit
-
Commit 8d4516904b39 ("watchdog: Fix CPU hotplug regression") causes an
oops or hard lockup when doingecho 0 > /proc/sys/kernel/nmi_watchdog
echo 1 > /proc/sys/kernel/nmi_watchdogand 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/stateBugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=51661
Cc: # v3.7
Cc: Norbert Warmuth
Cc: Joseph Salisbury
Cc: Thomas Gleixner
Signed-off-by: Bjørn Mork
Signed-off-by: Linus Torvalds
