15 Oct, 2014
1 commit
-
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
-
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
-
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
-
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
-
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
-
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
-
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
18 Dec, 2012
1 commit
-
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
Cc: Don Zickus
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
05 Dec, 2012
1 commit
-
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
Tested-by: Joseph Salisbury
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
27 Nov, 2012
1 commit
-
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: 0xEE6B2800case2:
set watchdog_thresh is 20, the sample value will be: 0x1 DCD6 5000In 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
Acked-by: Don Zickus
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
13 Aug, 2012
1 commit
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Signed-off-by: Thomas Gleixner
Cc: Peter Zijlstra
Cc: Srivatsa S. Bhat
Cc: Rusty Russell
Reviewed-by: Paul E. McKenney
Cc: Namhyung Kim
Link: http://lkml.kernel.org/r/20120716103948.563736676@linutronix.de
Signed-off-by: Thomas Gleixner
09 Aug, 2012
1 commit
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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
31 Jul, 2012
1 commit
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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
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: "Rafael J. Wysocki"
Cc: Don Zickus
Cc: Mandeep Singh Baines
Cc: Srivatsa S. Bhat
Cc: Anshuman Khandual
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
14 Jun, 2012
1 commit
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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 CPUsV2: 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 upsReported-and-tested-by: Nathan Zimmer
Signed-off-by: Don Zickus
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
08 Apr, 2012
1 commit
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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
Signed-off-by: Marcelo Tosatti
Signed-off-by: Avi Kivity
24 Mar, 2012
3 commits
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Revelation from Peter.
Cc: Peter Zijlstra
Cc: Don Zickus
Cc: Ingo Molnar
Cc: Thomas Gleixner
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
It fixes some 80-col wordwrappings and adds some consistency.
Cc: Ingo Molnar
Cc: Peter Zijlstra
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
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
Cc: Peter Zijlstra
Reviewed-by: Mandeep Singh Baines
Signed-off-by: Michal Hocko
Signed-off-by: Don Zickus
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
11 Feb, 2012
1 commit
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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
Signed-off-by: Don Zickus
Link: http://lkml.kernel.org/r/1328827342-6253-3-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar
27 Jan, 2012
1 commit
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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 ea 69 dd ff 4c 29 e8 48 89 c7 e8 0f bc da ff 49 89 c4 49 89This 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
Cc: dzickus@redhat.com
Cc: Linus Torvalds
Cc: Andrew Morton
Link: http://lkml.kernel.org/r/1327586134-11926-1-git-send-email-prarit@redhat.com
Signed-off-by: Ingo Molnar
01 Nov, 2011
1 commit
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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 usedthese functions are static and are used only in sysctl handler, so move
them inside #ifdef CONFIG_SYSCTL tooSigned-off-by: Vasily Averin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
18 Sep, 2011
1 commit
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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
Signed-off-by: Thomas Gleixner
Signed-off-by: Peter Zijlstra
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1109121337461.2723@ionos
Signed-off-by: Ingo Molnar