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Oleg Nesterov 6027ce497d hung_task: fix the broken rcu_lock_break() logic 
check_hung_uninterruptible_tasks()->rcu_lock_break() introduced by
"softlockup: check all tasks in hung_task" commit ce9dbe24 looks
absolutely wrong.

	- rcu_lock_break() does put_task_struct(). If the task has exited
	  it is not safe to even read its ->state, nothing protects this
	  task_struct.

	- The TASK_DEAD checks are wrong too. Contrary to the comment, we
	  can't use it to check if the task was unhashed. It can be unhashed
	  without TASK_DEAD, or it can be valid with TASK_DEAD.

	  For example, an autoreaping task can do release_task(current)
	  long before it sets TASK_DEAD in do_exit().

	  Or, a zombie task can have ->state == TASK_DEAD but release_task()
	  was not called, and in this case we must not break the loop.

Change this code to check pid_alive() instead, and do this before we drop
the reference to the task_struct.

Note: while_each_thread() under rcu_read_lock() is not really safe, it can
livelock.  This will be fixed later, but fortunately in this case the
"max_count" logic saves us anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Mandeep Singh Baines <msb@google.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-05 15:49:42 -08:00
..
debug module: struct module_ref should contains long fields 2012-01-13 09:32:14 +10:30
events perf/hwbp: Fix a possible memory leak 2012-02-28 09:52:54 +01:00
gcov gcov: disable CONSTRUCTORS for UML 2011-07-26 16:49:45 -07:00
irq genirq: Handle pending irqs in irq_startup() 2012-02-15 11:56:59 +01:00
power PM / Freezer: Thaw only kernel threads if freezing of kernel threads fails 2012-02-04 22:23:05 +01:00
sched CPU hotplug, cpusets, suspend: Don't touch cpusets during suspend/resume 2012-02-27 11:38:13 +01:00
time Merge branch 'rcu/fixes-for-v3.2' into rcu/urgent 2012-01-16 09:41:18 -08:00
trace Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-15 11:26:35 -08:00
.gitignore
acct.c Merge branch 'for-linus2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-01-08 12:19:57 -08:00
async.c kernel/async: remove redundant declaration. 2012-01-13 09:32:18 +10:30
audit_tree.c audit_tree,rcu: Convert call_rcu(__put_tree) to kfree_rcu() 2011-07-20 14:10:11 -07:00
audit_watch.c kill path_lookup() 2011-03-14 09:15:23 -04:00
audit.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit 2012-01-17 16:41:31 -08:00
audit.h audit: remove AUDIT_SETUP_CONTEXT as it isn't used 2012-01-17 16:16:57 -05:00
auditfilter.c audit: allow interfield comparison in audit rules 2012-01-17 16:17:01 -05:00
auditsc.c kernel-doc: fix new warnings in auditsc.c 2012-01-23 08:44:53 -08:00
backtracetest.c
bounds.c memcg: remove direct page_cgroup-to-page pointer 2011-03-23 19:46:28 -07:00
capability.c Revert "capabitlies: ns_capable can use the cap helpers rather than lsm call" 2012-01-17 10:19:41 -08:00
cgroup_freezer.c Merge branch 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2012-01-09 12:59:24 -08:00
cgroup.c Merge branch 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2012-01-09 12:59:24 -08:00
compat.c kernel: Fix files explicitly needing EXPORT_SYMBOL infrastructure 2011-10-31 19:30:05 -04:00
configs.c kernel/configs.c: include MODULE_*() when CONFIG_IKCONFIG_PROC=n 2011-07-25 20:57:15 -07:00
cpu_pm.c cpu_pm: call notifiers during suspend 2011-09-23 12:05:29 +05:30
cpu.c Merge branch 'pm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm 2012-01-08 13:10:57 -08:00
cpuset.c Merge branch 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2012-01-09 12:59:24 -08:00
crash_dump.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
cred.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
delayacct.c KVM: Steal time implementation 2011-07-14 12:59:14 +03:00
dma.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
elfcore.c
exec_domain.c
exit.c sched: Fix ancient race in do_exit() 2012-01-27 11:55:36 +01:00
extable.c extable, core_kernel_data(): Make sure all archs define _sdata 2011-05-20 08:56:56 +02:00
fork.c vfork: kill PF_STARTING 2012-03-05 15:49:42 -08:00
freezer.c freezer: kill unused set_freezable_with_signal() 2011-11-23 09:28:17 -08:00
futex_compat.c userns: user namespaces: convert several capable() calls 2011-03-23 19:47:08 -07:00
futex.c futex: Fix uninterruptible loop due to gate_area 2011-12-31 11:48:28 -08:00
groups.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
hrtimer.c Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2011-11-28 08:43:52 -08:00
hung_task.c hung_task: fix the broken rcu_lock_break() logic 2012-03-05 15:49:42 -08:00
irq_work.c kernel: fix two implicit header assumptions in irq_work.c 2011-10-31 09:20:12 -04:00
itimer.c [S390] cputime: add sparse checking and cleanup 2011-12-15 14:56:19 +01:00
jump_label.c Merge remote-tracking branch 'tip/perf/core' into kvm-updates/3.3 2011-12-27 11:22:24 +02:00
kallsyms.c Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-25 17:52:22 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks arch:Kconfig.locks Remove unused config option. 2011-04-10 17:01:05 +02:00
Kconfig.preempt sched: Isolate preempt counting in its own config option 2011-06-10 15:15:40 +02:00
kexec.c kdump: crashk_res init check for /sys/kernel/kexec_crash_size 2012-01-12 20:13:11 -08:00
kfifo.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
kmod.c Merge branch 'pm-sleep' into pm-for-linus 2011-12-25 23:42:20 +01:00
kprobes.c kprobes: return proper error code from register_kprobe() 2012-03-05 15:49:42 -08:00
ksysfs.c kernel: ksysfs.c is implicitly using stat.h 2011-10-31 09:20:13 -04:00
kthread.c freezer: kill unused set_freezable_with_signal() 2011-11-23 09:28:17 -08:00
latencytop.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lockdep_internals.h
lockdep_proc.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lockdep_states.h
lockdep.c Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-06 08:02:58 -08:00
Makefile PM: Make sysrq-o be available for CONFIG_PM unset 2012-01-14 00:33:03 +01:00
module.c error: implicit declaration of function 'module_flags_taint' 2012-01-15 16:21:07 -08:00
mutex-debug.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mutex-debug.h mutex: Use p->on_cpu for the adaptive spin 2011-04-14 08:52:33 +02:00
mutex.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mutex.h mutex: Use p->on_cpu for the adaptive spin 2011-04-14 08:52:33 +02:00
notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
nsproxy.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
padata.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
panic.c panic: don't print redundant backtraces on oops 2012-01-12 20:13:11 -08:00
params.c module: make module param bint handle nul value 2012-02-14 11:02:15 +10:30
pid_namespace.c sysctl: add the kernel.ns_last_pid control 2012-01-12 20:13:11 -08:00
pid.c vfs: fix panic in __d_lookup() with high dentry hashtable counts 2012-02-13 20:45:38 -05:00
posix-cpu-timers.c [S390] cputime: add sparse checking and cleanup 2011-12-15 14:56:19 +01:00
posix-timers.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
printk.c kmsg_dump: don't run on non-error paths by default 2012-03-05 15:49:42 -08:00
profile.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
ptrace.c Merge branch 'for-linus' of git://selinuxproject.org/~jmorris/linux-security 2012-01-14 18:36:33 -08:00
range.c range: fix bogus misuse of module.h to get printk() 2011-10-31 09:20:11 -04:00
rcu.h rcu: Deconfuse dynticks entry-exit tracing 2011-12-11 10:31:42 -08:00
rcupdate.c rcu: Detect illegal rcu dereference in extended quiescent state 2011-12-11 10:31:30 -08:00
rcutiny_plugin.h rcu: Apply ACCESS_ONCE() to rcu_boost() return value 2011-12-11 10:33:19 -08:00
rcutiny.c rcu: Augment rcu_batch_end tracing for idle and callback state 2011-12-11 10:32:22 -08:00
rcutorture.c rcu: Add missing __cpuinit annotation in rcutorture code 2012-01-16 09:44:05 -08:00
rcutree_plugin.h rcu: Apply ACCESS_ONCE() to rcu_boost() return value 2011-12-11 10:33:19 -08:00
rcutree_trace.c rcu: Track idleness independent of idle tasks 2011-12-11 10:31:24 -08:00
rcutree.c rcu: Augment rcu_batch_end tracing for idle and callback state 2011-12-11 10:32:22 -08:00
rcutree.h rcu: Keep invoking callbacks if CPU otherwise idle 2011-12-11 10:32:09 -08:00
relay.c relay: prevent integer overflow in relay_open() 2012-02-10 09:04:49 +01:00
res_counter.c net: introduce res_counter_charge_nofail() for socket allocations 2012-01-22 15:08:46 -05:00
resource.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
rtmutex_common.h rtmutex: Simplify PI algorithm and make highest prio task get lock 2011-01-27 21:13:51 -05:00
rtmutex-debug.c lockdep, rtmutex, bug: Show taint flags on error 2011-12-06 08:16:49 +01:00
rtmutex-debug.h
rtmutex-tester.c rtmutex-tester: convert sysdev_class to a regular subsystem 2011-12-14 14:54:22 -08:00
rtmutex.c Revert "rcu: Permit rt_mutex_unlock() with irqs disabled" 2011-12-11 10:33:18 -08:00
rtmutex.h
rwsem.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
seccomp.c seccomp: audit abnormal end to a process due to seccomp 2012-01-17 16:16:55 -05:00
semaphore.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
signal.c user namespace: make signal.c respect user namespaces 2012-01-10 16:30:54 -08:00
smp.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
softirq.c rcu: Fix early call to rcu_idle_enter() 2011-12-11 10:31:38 -08:00
spinlock.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
srcu.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
stacktrace.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
stop_machine.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
sys_ni.c Cross Memory Attach 2011-10-31 17:30:44 -07:00
sys.c c/r: prctl: add PR_SET_MM codes to set up mm_struct entries 2012-01-12 20:13:13 -08:00
sysctl_binary.c binary_sysctl(): fix memory leak 2011-12-20 10:25:04 -08:00
sysctl_check.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
sysctl.c x86: Panic on detection of stack overflow 2011-12-05 11:37:47 +01:00
taskstats.c Make TASKSTATS require root access 2011-09-19 17:04:37 -07:00
test_kprobes.c
time.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
timeconst.pl
timer.c Merge branch 'core-debugobjects-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-06 07:53:34 -08:00
tracepoint.c tracepoints/module: Fix disabling tracepoints with taint CRAP or OOT 2012-01-16 11:35:57 -05:00
tsacct.c [S390] cputime: add sparse checking and cleanup 2011-12-15 14:56:19 +01:00
uid16.c userns: user namespaces: convert several capable() calls 2011-03-23 19:47:08 -07:00
up.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user_namespace.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user-return-notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
utsname_sysctl.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
utsname.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
wait.c lockdep/waitqueues: Add better annotation 2011-12-21 10:07:39 +01:00
watchdog.c bugs, x86: Fix printk levels for panic, softlockups and stack dumps 2012-01-26 21:28:45 +01:00
workqueue_sched.h
workqueue.c workqueue: make alloc_workqueue() take printf fmt and args for name 2012-01-10 16:30:54 -08:00