Heiko Carstens 61ab25447a nohz: Fix printk_needs_cpu() return value on offline cpus ... This patch fixes a hang observed with 2.6.32 kernels where timers got enqueued on offline cpus. printk_needs_cpu() may return 1 if called on offline cpus. When a cpu gets offlined it schedules the idle process which, before killing its own cpu, will call tick_nohz_stop_sched_tick(). That function in turn will call printk_needs_cpu() in order to check if the local tick can be disabled. On offline cpus this function should naturally return 0 since regardless if the tick gets disabled or not the cpu will be dead short after. That is besides the fact that __cpu_disable() should already have made sure that no interrupts on the offlined cpu will be delivered anyway. In this case it prevents tick_nohz_stop_sched_tick() to call select_nohz_load_balancer(). No idea if that really is a problem. However what made me debug this is that on 2.6.32 the function get_nohz_load_balancer() is used within __mod_timer() to select a cpu on which a timer gets enqueued. If printk_needs_cpu() returns 1 then the nohz_load_balancer cpu doesn't get updated when a cpu gets offlined. It may contain the cpu number of an offline cpu. In turn timers get enqueued on an offline cpu and not very surprisingly they never expire and cause system hangs. This has been observed 2.6.32 kernels. On current kernels __mod_timer() uses get_nohz_timer_target() which doesn't have that problem. However there might be other problems because of the too early exit tick_nohz_stop_sched_tick() in case a cpu goes offline. Easiest way to fix this is just to test if the current cpu is offline and call printk_tick() directly which clears the condition. Alternatively I tried a cpu hotplug notifier which would clear the condition, however between calling the notifier function and printk_needs_cpu() something could have called printk() again and the problem is back again. This seems to be the safest fix. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: stable@kernel.org LKML-Reference: <20101126120235.406766476@de.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>		2010-11-26 15:03:12 +01:00
..
debug	debug_core,x86,blackfin: Clean up hw debug disable API	2010-10-29 13:14:41 -05:00
gcov	llseek: automatically add .llseek fop	2010-10-15 15:53:27 +02:00
irq	Merge branches 'irq-core-for-linus' and 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2010-10-31 20:40:24 -04:00
power	PM / OPP: Hide OPP configuration when SoCs do not provide an implementation	2010-11-11 01:51:26 +01:00
time	ntp: Clamp PLL update interval	2010-09-09 20:48:37 +02:00
trace	Merge branch 'for-linus' of git://git390.marist.edu/pub/scm/linux-2.6	2010-11-16 09:27:13 -08:00
.gitignore
acct.c	pass a struct path to vfs_statfs	2010-08-09 16:48:42 -04:00
async.c	async: use workqueue for worker pool	2010-07-14 11:29:46 +02:00
audit_tree.c	in untag_chunk() we need to do alloc_chunk() a bit earlier	2010-10-30 02:18:32 -04:00
audit_watch.c	audit: make functions static	2010-10-30 01:42:19 -04:00
audit.c	audit: Use rcu for task lookup protection	2010-10-30 08:45:42 -04:00
audit.h	audit: make functions static	2010-10-30 01:42:19 -04:00
auditfilter.c	Audit: add support to match lsm labels on user audit messages	2010-10-30 01:41:57 -04:00
auditsc.c	audit mmap	2010-10-30 08:45:43 -04:00
backtracetest.c
bounds.c
capability.c	sched: Remove remaining USER_SCHED code	2010-04-02 20:12:00 +02:00
cgroup_freezer.c	cgroup_freezer: update_freezer_state() does incorrect state transitions	2010-10-27 18:03:08 -07:00
cgroup.c	convert cgroup and cpuset	2010-10-29 04:17:06 -04:00
compat.c	compat: Make compat_alloc_user_space() incorporate the access_ok()	2010-09-14 16:08:45 -07:00
configs.c	llseek: automatically add .llseek fop	2010-10-15 15:53:27 +02:00
cpu.c	sched: adjust when cpu_active and cpuset configurations are updated during cpu on/offlining	2010-06-08 21:40:36 +02:00
cpuset.c	convert cgroup and cpuset	2010-10-29 04:17:06 -04:00
cred.c	signals: move cred_guard_mutex from task_struct to signal_struct	2010-10-27 18:03:12 -07:00
delayacct.c
dma.c
elfcore.c	elf coredump: add extended numbering support	2010-03-06 11:26:46 -08:00
exec_domain.c	sys_personality: remove the bogus checks in sys_personality()->__set_personality() path	2010-08-09 20:45:05 -07:00
exit.c	posix-cpu-timers: workaround to suppress the problems with mt exec	2010-11-05 14:16:03 -07:00
extable.c
fork.c	signals: move cred_guard_mutex from task_struct to signal_struct	2010-10-27 18:03:12 -07:00
freezer.c
futex_compat.c	futex: Address compiler warnings in exit_robust_list	2010-11-10 13:27:50 +01:00
futex.c	futex: Address compiler warnings in exit_robust_list	2010-11-10 13:27:50 +01:00
groups.c	kernel/groups.c: fix integer overflow in groups_search	2010-09-09 18:57:24 -07:00
hrtimer.c	hrtimer: Preserve timer state in remove_hrtimer()	2010-10-14 13:29:59 +02:00
hung_task.c	lockup detector: Fix grammar by adding a missing "to" in the comments	2010-08-17 09:11:52 +02:00
hw_breakpoint.c	perf, hw_breakpoint: Fix crash in hw_breakpoint creation	2010-10-18 19:58:55 +02:00
irq_work.c	irq_work: Add generic hardirq context callbacks	2010-10-18 19:58:50 +02:00
itimer.c
jump_label.c	jump label: Make arch_jump_label_text_poke_early() optional	2010-10-29 12:56:13 -04:00
kallsyms.c	kernel: make /proc/kallsyms mode 400 to reduce ease of attacking	2010-11-16 19:06:01 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kexec.c	use clear_page()/copy_page() in favor of memset()/memcpy() on whole pages	2010-10-26 16:52:13 -07:00
kfifo.c	kfifo: fix scatterlist usage	2010-10-01 10:50:58 -07:00
kmod.c	Make do_execve() take a const filename pointer	2010-08-17 18:07:43 -07:00
kprobes.c	jump label: Fix error with preempt disable holding mutex	2010-10-29 12:55:55 -04:00
ksysfs.c	sysfs: add struct file* to bin_attr callbacks	2010-05-21 09:37:31 -07:00
kthread.c	kthread: implement kthread_data()	2010-06-29 10:07:09 +02:00
latencytop.c	latencytop: fix per task accumulator	2010-11-12 07:55:31 -08:00
lockdep_internals.h	lockdep: No need to disable preemption in debug atomic ops	2010-05-04 05:38:16 +02:00
lockdep_proc.c	lockstat: Make lockstat counting per cpu	2010-04-06 00:15:37 +02:00
lockdep_states.h
lockdep.c	lockdep: Check the depth of subclass	2010-10-18 18:44:26 +02:00
Makefile	Merge branch 'core-memblock-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2010-10-21 18:52:11 -07:00
module.c	(trivial) Fix compiler warning in kernel/modules.c	2010-10-27 20:33:05 +10:30
mutex-debug.c
mutex-debug.h
mutex.c	mutex: Fix annotations to include it in kernel-locking docbook	2010-09-03 08:19:51 +02:00
mutex.h
notifier.c	sched: Use lockdep-based checking on rcu_dereference()	2010-02-25 10:34:26 +01:00
ns_cgroup.c	cgroup: notify ns_cgroup deprecated	2010-10-27 18:03:09 -07:00
nsproxy.c	include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h	2010-03-30 22:02:32 +09:00
padata.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6	2010-08-04 15:23:14 -07:00
panic.c	lib/bug.c: add oops end marker to WARN implementation	2010-08-11 08:59:22 -07:00
params.c	param: locking for kernel parameters	2010-08-11 23:04:20 +09:30
perf_event.c	perf_events: Fix time tracking in samples	2010-11-10 22:58:39 +01:00
pid_namespace.c	include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h	2010-03-30 22:02:32 +09:00
pid.c	Add RCU check for find_task_by_vpid().	2010-08-19 17:18:02 -07:00
pm_qos_params.c	PM / PM QoS: Fix reversed min and max	2010-11-15 22:45:22 +01:00
posix-cpu-timers.c	Merge branch 'writable_limits' of git://decibel.fi.muni.cz/~xslaby/linux	2010-08-10 12:07:51 -07:00
posix-timers.c	posix_timer: Move copy_to_user(created_timer_id) down in timer_create()	2010-07-23 15:08:12 +02:00
printk.c	nohz: Fix printk_needs_cpu() return value on offline cpus	2010-11-26 15:03:12 +01:00
profile.c	llseek: automatically add .llseek fop	2010-10-15 15:53:27 +02:00
ptrace.c	signals: move cred_guard_mutex from task_struct to signal_struct	2010-10-27 18:03:12 -07:00
range.c	kernel/range.c: fix clean_sort_range() for the case of full array	2010-11-12 07:55:31 -08:00
rcupdate.c	Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/rcu	2010-10-07 09:43:11 +02:00
rcutiny_plugin.h	rcu: performance fixes to TINY_PREEMPT_RCU callback checking	2010-08-27 10:51:17 -07:00
rcutiny.c	rcu: Add a TINY_PREEMPT_RCU	2010-08-20 08:55:00 -07:00
rcutorture.c	rcu: fix sparse errors in rcutorture.c	2010-09-23 09:16:42 -07:00
rcutree_plugin.h	rcu: fix _oddness handling of verbose stall warnings	2010-09-02 16:15:30 -07:00
rcutree_trace.c	rcu: Add tracing data to support queueing models	2010-09-23 09:16:53 -07:00
rcutree.c	rcu: using ACCESS_ONCE() to observe the jiffies_stall/rnp->qsmask value	2010-10-07 10:41:06 -07:00
rcutree.h	rcu: Add tracing data to support queueing models	2010-09-23 09:16:53 -07:00
relay.c	Clean up relay_alloc_page_array() slightly by using vzalloc rather than vmalloc and memset	2010-11-05 08:21:34 -07:00
res_counter.c	include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h	2010-03-30 22:02:32 +09:00
resource.c	Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6	2010-10-28 11:59:52 -07:00
rtmutex_common.h
rtmutex-debug.c
rtmutex-debug.h
rtmutex-tester.c	rtmutex-tester: make it build without BKL	2010-10-19 11:29:56 +02:00
rtmutex.c
rtmutex.h
rwsem.c
sched_clock.c	sched_clock: Add local_clock() API and improve documentation	2010-06-09 10:34:49 +02:00
sched_cpupri.c	sched: No need for bootmem special cases	2010-07-17 12:06:22 +02:00
sched_cpupri.h	sched: No need for bootmem special cases	2010-07-17 12:06:22 +02:00
sched_debug.c	sched: Use correct macro to display sched_child_runs_first in /proc/sched_debug	2010-07-21 21:46:12 +02:00
sched_fair.c	sched: Fix idle balancing	2010-11-18 13:12:33 +01:00
sched_features.h	sched: Remove irq time from available CPU power	2010-10-18 20:52:27 +02:00
sched_idletask.c	sched: Cure load average vs NO_HZ woes	2010-04-23 11:02:02 +02:00
sched_rt.c	sched: Do not account irq time to current task	2010-10-18 20:52:26 +02:00
sched_stats.h	sched_stat: Update sched_info_queue/dequeue() code comments	2010-10-24 13:29:01 +02:00
sched_stoptask.c	sched: Fix cross-sched-class wakeup preemption	2010-11-11 14:37:23 +01:00
sched.c	sched: Fix cross-sched-class wakeup preemption	2010-11-11 14:37:23 +01:00
seccomp.c
semaphore.c
signal.c	signals: annotate lock context change on ptrace_stop()	2010-10-27 18:03:12 -07:00
smp.c	Typedef SMP call function pointer	2010-10-27 17:28:36 +01:00
softirq.c	Merge branch 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2010-10-27 18:48:00 -07:00
spinlock.c
srcu.c	kernel: Remove undead ifdef CONFIG_DEBUG_LOCK_ALLOC	2010-09-23 09:14:51 -07:00
stacktrace.c
stop_machine.c	stop_machine: convert cpu notifier to return encapsulate errno value	2010-10-26 16:52:15 -07:00
sys_ni.c	powerpc: define a compat_sys_recv cond_syscall	2010-09-23 17:03:55 +10:00
sys.c	pid: make setpgid() system call use RCU read-side critical section	2010-08-31 17:00:18 -07:00
sysctl_binary.c	sysctl: don't use own implementation of hex_to_bin()	2010-05-25 08:07:05 -07:00
sysctl_check.c	sysctl: min/max bounds are optional	2010-10-15 14:42:24 -07:00
sysctl.c	kernel/sysctl.c: Fix build failure with !CONFIG_PRINTK	2010-11-16 07:56:09 -08:00
taskstats.c	taskstats: split fill_pid function	2010-10-27 18:03:17 -07:00
test_kprobes.c	kprobes: Fix selftest to clear flags field for reusing probes	2010-10-14 08:55:27 +02:00
time.c	time: Kill off CONFIG_GENERIC_TIME	2010-07-27 12:40:54 +02:00
timeconst.pl
timer.c	irq_work: Add generic hardirq context callbacks	2010-10-18 19:58:50 +02:00
tracepoint.c	jump_label: Use more consistent naming	2010-10-18 19:58:56 +02:00
tsacct.c	taskstats: use real microsecond granularity for CPU times	2010-10-27 18:03:17 -07:00
uid16.c
up.c
user_namespace.c	user_ns: Introduce user_nsmap_uid and user_ns_map_gid.	2010-06-16 14:55:34 -07:00
user-return-notifier.c
user.c	kernel/user.c: add lock release annotation on free_user()	2010-10-26 16:52:15 -07:00
utsname_sysctl.c
utsname.c
wait.c	docbook: add more wait/wake/completion to device-drivers docbook	2010-10-26 17:32:41 -07:00
watchdog.c	watchdog: Fix section mismatch and potential undefined behavior.	2010-11-05 17:45:35 -07:00
workqueue_sched.h	workqueue: implement concurrency managed dynamic worker pool	2010-06-29 10:07:14 +02:00
workqueue.c	workqueues: s/ON_STACK/ONSTACK/	2010-10-26 16:52:14 -07:00