Paul E. McKenney 389abd48ef rcu: Avoid RCU-preempt expedited grace-period botch ... Because rcu_read_unlock_special() samples rcu_preempted_readers_exp(rnp) after dropping rnp->lock, the following sequence of events is possible: 1. Task A exits its RCU read-side critical section, and removes itself from the ->blkd_tasks list, releases rnp->lock, and is then preempted. Task B remains on the ->blkd_tasks list, and blocks the current expedited grace period. 2. Task B exits from its RCU read-side critical section and removes itself from the ->blkd_tasks list. Because it is the last task blocking the current expedited grace period, it ends that expedited grace period. 3. Task A resumes, and samples rcu_preempted_readers_exp(rnp) which of course indicates that nothing is blocking the nonexistent expedited grace period. Task A is again preempted. 4. Some other CPU starts an expedited grace period. There are several tasks blocking this expedited grace period queued on the same rcu_node structure that Task A was using in step 1 above. 5. Task A examines its state and incorrectly concludes that it was the last task blocking the expedited grace period on the current rcu_node structure. It therefore reports completion up the rcu_node tree. 6. The expedited grace period can then incorrectly complete before the tasks blocked on this same rcu_node structure exit their RCU read-side critical sections. Arbitrarily bad things happen. This commit therefore takes a snapshot of rcu_preempted_readers_exp(rnp) prior to dropping the lock, so that only the last task thinks that it is the last task, thus avoiding the failure scenario laid out above. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>		2011-12-11 10:31:21 -08:00
..
debug	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
events	perf: Do no try to schedule task events if there are none	2011-12-07 16:31:22 +01:00
gcov
irq	genirq: Fix race condition when stopping the irq thread	2011-12-02 11:54:24 +01:00
power	PM / Hibernate: Do not leak memory in error/test code paths	2011-11-23 21:03:38 +01:00
time	alarmtimers: Fix time comparison	2011-12-06 11:38:32 +01:00
trace	ftrace: Fix hash record accounting bug	2011-12-05 13:28:47 -05:00
.gitignore
acct.c
async.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
audit.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
audit.h
audit_tree.c
audit_watch.c
auditfilter.c
auditsc.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
backtracetest.c
bounds.c
capability.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
cgroup.c	memcg: replace ss->id_lock with a rwlock	2011-11-02 16:07:03 -07:00
cgroup_freezer.c	cgroup_freezer: fix freezing groups with stopped tasks	2011-11-24 11:58:22 -08:00
compat.c	kernel: Fix files explicitly needing EXPORT_SYMBOL infrastructure	2011-10-31 19:30:05 -04:00
configs.c
cpu.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
cpu_pm.c	cpu_pm: call notifiers during suspend	2011-09-23 12:05:29 +05:30
cpuset.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
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
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	oom: remove oom_disable_count	2011-10-31 17:30:45 -07:00
extable.c
fork.c	writeback: remove vm_dirties and task->dirties	2011-11-17 20:49:06 +08:00
freezer.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
futex.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
futex_compat.c
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	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
irq_work.c	kernel: fix two implicit header assumptions in irq_work.c	2011-10-31 09:20:12 -04:00
itimer.c
jump_label.c	jump_label: jump_label_inc may return before the code is patched	2011-12-05 13:28:46 -05:00
kallsyms.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kexec.c	[S390] kdump: Add infrastructure for unmapping crashkernel memory	2011-10-30 15:16:42 +01:00
kfifo.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
kmod.c	kmod: prevent kmod_loop_msg overflow in __request_module()	2011-10-26 13:10:39 +10:30
kprobes.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
ksysfs.c	kernel: ksysfs.c is implicitly using stat.h	2011-10-31 09:20:13 -04:00
kthread.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
latencytop.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
lockdep.c	lockdep, kmemcheck: Annotate ->lock in lockdep_init_map()	2011-12-06 18:18:13 +01:00
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
Makefile	Merge branch 'devel-stable' of http://ftp.arm.linux.org.uk/pub/linux/arm/kernel/git-cur/linux-2.6-arm	2011-10-28 12:02:27 -07:00
module.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
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.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
mutex.h
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	module,bug: Add TAINT_OOT_MODULE flag for modules not built in-tree	2011-11-07 07:54:42 +10:30
params.c	kernel: params.c needs module.h not moduleparam.h	2011-10-31 09:20:13 -04:00
pid.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
pid_namespace.c
posix-cpu-timers.c	Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2011-10-26 16:17:32 +02:00
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	printk: avoid double lock acquire	2011-12-09 07:50:28 -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	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
range.c	range: fix bogus misuse of module.h to get printk()	2011-10-31 09:20:11 -04:00
rcu.h	rcu: Add grace-period, quiescent-state, and call_rcu trace events	2011-09-28 21:38:21 -07:00
rcupdate.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
rcutiny.c	kernel: fix up module header handling in rcutiny files	2011-10-31 09:20:13 -04:00
rcutiny_plugin.h	kernel: fix up module header handling in rcutiny files	2011-10-31 09:20:13 -04:00
rcutorture.c	rcu: Make rcu_torture_boost() exit loops at end of test	2011-09-28 21:38:46 -07:00
rcutree.c	rcu: ->signaled better named ->fqs_state	2011-12-11 10:31:20 -08:00
rcutree.h	rcu: ->signaled better named ->fqs_state	2011-12-11 10:31:20 -08:00
rcutree_plugin.h	rcu: Avoid RCU-preempt expedited grace-period botch	2011-12-11 10:31:21 -08:00
rcutree_trace.c	rcu: ->signaled better named ->fqs_state	2011-12-11 10:31:20 -08:00
relay.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
res_counter.c
resource.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
rtmutex-debug.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
rtmutex-debug.h
rtmutex-tester.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
rtmutex.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
rtmutex.h
rtmutex_common.h
rwsem.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
sched.c	sched: Set the command name of the idle tasks in SMP kernels	2011-11-14 12:50:43 +01:00
sched_autogroup.c
sched_autogroup.h
sched_clock.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
sched_cpupri.c	sched/cpupri: Remove cpupri->pri_active	2011-08-14 12:01:11 +02:00
sched_cpupri.h	sched/cpupri: Remove cpupri->pri_active	2011-08-14 12:01:11 +02:00
sched_debug.c
sched_fair.c	sched: Fix buglet in return_cfs_rq_runtime()	2011-11-16 08:43:45 +01:00
sched_features.h	sched, rt: Provide means of disabling cross-cpu bandwidth sharing	2011-11-14 12:50:40 +01:00
sched_idletask.c
sched_rt.c	sched, rt: Provide means of disabling cross-cpu bandwidth sharing	2011-11-14 12:50:40 +01:00
sched_stats.h	locking, sched: Annotate thread_group_cputimer as raw	2011-09-13 11:11:55 +02:00
sched_stoptask.c	sched: Implement hierarchical task accounting for SCHED_OTHER	2011-08-14 12:01:13 +02:00
seccomp.c
semaphore.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
signal.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
smp.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
softirq.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
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.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
sysctl.c	Merge branch 'akpm' (Andrew's incoming)	2011-10-31 17:46:07 -07:00
sysctl_binary.c	ipv4: NET_IPV4_ROUTE_GC_INTERVAL removal	2011-10-03 14:13:01 -04:00
sysctl_check.c	xfs: remove subdirectories	2011-08-12 16:21:35 -05:00
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	sys_getppid: add missing rcu_dereference	2011-12-09 07:50:29 -08:00
tracepoint.c	Tracepoint: Dissociate from module mutex	2011-08-10 20:38:14 -04:00
tsacct.c	Make taskstats round statistics down to nearest 1k bytes/events	2011-09-19 17:10:57 -07:00
uid16.c
up.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
user_namespace.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
utsname.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
wait.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
watchdog.c	watchdog: move watchdog_*_all_cpus under CONFIG_SYSCTL	2011-10-31 17:30:53 -07:00
workqueue.c	kernel: Map most files to use export.h instead of module.h	2011-10-31 09:20:12 -04:00
workqueue_sched.h