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Don Zickus b94f51183b kernel/watchdog: prevent false hardlockup on overloaded system 
On an overloaded system, it is possible that a change in the watchdog
threshold can be delayed long enough to trigger a false positive.

This can easily be achieved by having a cpu spinning indefinitely on a
task, while another cpu updates watchdog threshold.

What happens is while trying to park the watchdog threads, the hrtimers
on the other cpus trigger and reprogram themselves with the new slower
watchdog threshold.  Meanwhile, the nmi watchdog is still programmed
with the old faster threshold.

Because the one cpu is blocked, it prevents the thread parking on the
other cpus from completing, which is needed to shutdown the nmi watchdog
and reprogram it correctly.  As a result, a false positive from the nmi
watchdog is reported.

Fix this by setting a park_in_progress flag to block all lockups until
the parking is complete.

Fix provided by Ulrich Obergfell.

[akpm@linux-foundation.org: s/park_in_progress/watchdog_park_in_progress/]
Link: http://lkml.kernel.org/r/1481041033-192236-1-git-send-email-dzickus@redhat.com
Signed-off-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>
2017-01-24 16:26:14 -08:00
..
bpf bpf: rework prog_digest into prog_tag 2017-01-16 14:03:31 -05:00
configs config: android: enable CONFIG_SECCOMP 2016-10-11 15:06:32 -07:00
debug kdb: call vkdb_printf() from vprintk_default() only when wanted 2016-12-14 16:04:08 -08:00
events perf/x86/intel: Account interrupts for PEBS errors 2017-01-14 11:06:49 +01:00
gcov gcov: add support for gcc version >= 6 2016-07-15 14:54:27 +09:00
irq genirq/affinity: Fix node generation from cpumask 2016-12-15 12:32:35 +01:00
livepatch livepatch/module: make TAINT_LIVEPATCH module-specific 2016-08-26 14:42:08 +02:00
locking Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
power Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
printk Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
rcu rcu: Narrow early boot window of illegal synchronous grace periods 2017-01-14 21:23:48 -08:00
sched ktime: Cleanup ktime_set() usage 2016-12-25 17:21:22 +01:00
time nohz: Fix collision between tick and other hrtimers 2017-01-11 10:41:33 +01:00
trace clocksource: Use a plain u64 instead of cycle_t 2016-12-25 11:04:12 +01:00
.gitignore
acct.c acct: check FMODE_CAN_WRITE 2015-04-11 22:27:55 -04:00
async.c
audit.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-12-17 18:44:00 -08:00
audit.h audit_log_{name,link_denied}: constify struct path 2016-12-05 19:00:38 -05:00
audit_fsnotify.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-12-17 18:44:00 -08:00
audit_tree.c Merge branch 'stable-4.10' of git://git.infradead.org/users/pcmoore/audit 2017-01-05 23:06:06 -08:00
audit_watch.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-12-17 18:44:00 -08:00
auditfilter.c audit: add support for session ID user filter 2016-11-29 15:10:12 -05:00
auditsc.c Merge branch 'stable-4.10' of git://git.infradead.org/users/pcmoore/audit 2016-12-14 14:06:40 -08:00
backtracetest.c
bounds.c
capability.c capability: export has_capability 2017-01-12 07:01:56 -07:00
cgroup.c cgroup: add support for eBPF programs 2016-11-25 16:25:52 -05:00
cgroup_freezer.c
cgroup_pids.c
compat.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
configs.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
context_tracking.c
cpu.c cpu/hotplug: Remove unused but set variable in _cpu_down() 2017-01-18 11:55:09 +01:00
cpu_pm.c
cpuset.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
crash_dump.c
cred.c cred: Reject inodes with invalid ids in set_create_file_as() 2016-06-30 18:05:09 -05:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
extable.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
fork.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
freezer.c freezer, oom: check TIF_MEMDIE on the correct task 2016-07-28 16:07:41 -07:00
futex.c ktime: Get rid of the union 2016-12-25 17:21:22 +01:00
futex_compat.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
groups.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
hung_task.c hung_task: decrement sysctl_hung_task_warnings only if it is positive 2016-12-12 18:55:09 -08:00
irq_work.c
jump_label.c jump_labels: API for flushing deferred jump label updates 2017-01-12 14:33:16 +01:00
kallsyms.c
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/mutex: Allow MUTEX_SPIN_ON_OWNER when DEBUG_MUTEXES 2016-10-25 11:31:51 +02:00
Kconfig.preempt
kcov.c kcov: make kcov work properly with KASLR enabled 2016-12-20 09:48:47 -08:00
kexec.c kexec: allow architectures to override boot mapping 2016-08-02 19:35:27 -04:00
kexec_core.c kexec: add cond_resched into kimage_alloc_crash_control_pages 2016-12-14 16:04:07 -08:00
kexec_file.c ima: on soft reboot, save the measurement list 2016-12-20 09:48:44 -08:00
kexec_internal.h kexec_file: Allow arch-specific memory walking for kexec_add_buffer 2016-11-30 23:14:57 +11:00
kmod.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
kprobes.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
ksysfs.c kexec: add a kexec_crash_loaded() function 2016-08-02 19:35:30 -04:00
kthread.c kthread: add __printf attributes 2016-12-12 18:55:06 -08:00
latencytop.c
Makefile Merge branch 'akpm' (patches from Andrew) 2016-12-14 17:25:18 -08:00
membarrier.c
memremap.c mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done} 2017-01-10 18:31:54 -08:00
module-internal.h
module.c taint/module: Fix problems when out-of-kernel driver defines true or false 2017-01-17 10:56:45 -08:00
module_signing.c
notifier.c Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-09-01 08:40:25 -07:00
nsproxy.c
padata.c padata: Remove unused but set variables 2016-10-25 11:08:10 +08:00
panic.c taint/module: Fix problems when out-of-kernel driver defines true or false 2017-01-17 10:56:45 -08:00
params.c
pid.c
pid_namespace.c pid: fix lockdep deadlock warning due to ucount_lock 2017-01-10 13:34:56 +13:00
profile.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
ptrace.c ptrace: Don't allow accessing an undumpable mm 2016-11-22 12:57:38 -06:00
range.c
reboot.c
relay.c relay: check array offset before using it 2016-12-14 16:04:08 -08:00
resource.c
seccomp.c Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2016-12-14 13:57:44 -08:00
signal.c signal: protect SIGNAL_UNKILLABLE from unintentional clearing. 2017-01-10 18:31:55 -08:00
smp.c kernel/smp: Tell the user we're bringing up secondary CPUs 2016-10-26 12:02:35 +02:00
smpboot.c kthread/smpboot: do not park in kthread_create_on_cpu() 2016-10-11 15:06:33 -07:00
smpboot.h
softirq.c softirq: Display IRQ_POLL for irq-poll statistics 2016-10-21 15:45:47 -06:00
stacktrace.c
stop_machine.c locking/core, stop_machine: Yield the CPU during stop machine() 2016-11-16 10:15:09 +01:00
sys.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
sys_ni.c move aio compat to fs/aio.c 2016-12-22 22:58:37 -05:00
sysctl.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
sysctl_binary.c sysctl: add KERN_CONT to deprecated_sysctl_warning() 2016-12-14 16:04:07 -08:00
task_work.c task_work: use READ_ONCE/lockless_dereference, avoid pi_lock if !task_works 2016-08-02 19:35:02 -04:00
taskstats.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-11-15 10:54:36 -05:00
test_kprobes.c
torture.c torture: Convert torture_shutdown() to hrtimer 2016-08-22 10:01:49 -07:00
tracepoint.c tracing: Have the reg function allow to fail 2016-12-09 09:13:30 -05:00
tsacct.c
ucount.c mntns: Add a limit on the number of mount namespaces. 2016-08-31 07:28:35 -05:00
uid16.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
up.c smp: Add function to execute a function synchronously on a CPU 2016-09-05 13:52:39 +02:00
user-return-notifier.c
user.c
user_namespace.c Merge branch 'nsfs-ioctls' into HEAD 2016-09-22 20:00:36 -05:00
utsname.c Merge branch 'nsfs-ioctls' into HEAD 2016-09-22 20:00:36 -05:00
utsname_sysctl.c sysctl: convert use of typedef ctl_table to struct ctl_table 2014-06-06 16:08:16 -07:00
watchdog.c kernel/watchdog: prevent false hardlockup on overloaded system 2017-01-24 16:26:14 -08:00
watchdog_hld.c kernel/watchdog: prevent false hardlockup on overloaded system 2017-01-24 16:26:14 -08:00
workqueue.c Merge branch 'for-4.9' into for-4.10 2016-10-19 12:12:40 -04:00
workqueue_internal.h