Paul E. McKenney db3a892099 rcu: fix race condition in synchronize_sched_expedited() ... The new (early 2010) implementation of synchronize_sched_expedited() uses try_stop_cpu() to force a context switch on every CPU. It also permits concurrent calls to synchronize_sched_expedited() to share a single call to try_stop_cpu() through use of an atomically incremented synchronize_sched_expedited_count variable. Unfortunately, this is subject to failure as follows: o Task A invokes synchronize_sched_expedited(), try_stop_cpus() succeeds, but Task A is preempted before getting to the atomic increment of synchronize_sched_expedited_count. o Task B also invokes synchronize_sched_expedited(), with exactly the same outcome as Task A. o Task C also invokes synchronize_sched_expedited(), again with exactly the same outcome as Tasks A and B. o Task D also invokes synchronize_sched_expedited(), but only gets as far as acquiring the mutex within try_stop_cpus() before being preempted, interrupted, or otherwise delayed. o Task E also invokes synchronize_sched_expedited(), but only gets to the snapshotting of synchronize_sched_expedited_count. o Tasks A, B, and C all increment synchronize_sched_expedited_count. o Task E fails to get the mutex, so checks the new value of synchronize_sched_expedited_count. It finds that the value has increased, so (wrongly) assumes that its work has been done, returning despite there having been no expedited grace period since it began. The solution is to have the lowest-numbered CPU atomically increment the synchronize_sched_expedited_count variable within the synchronize_sched_expedited_cpu_stop() function, which is under the protection of the mutex acquired by try_stop_cpus(). However, this also requires that piggybacking tasks wait for three rather than two instances of try_stop_cpu(), because we cannot control the order in which the per-CPU callback function occur. Cc: Tejun Heo <tj@kernel.org> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>		2010-11-29 22:02:00 -08:00
..
debug	Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2010-09-08 11:13:42 -07:00
gcov	gcov: fix null-pointer dereference for certain module types	2010-09-09 18:57:23 -07:00
irq	irq: Add new IRQ flag IRQF_NO_SUSPEND	2010-07-29 13:24:57 +02:00
power	Merge branch 'pm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/suspend-2.6	2010-09-11 15:50:53 -07:00
time	time: Workaround gcc loop optimization that causes 64bit div errors	2010-08-13 12:03:24 -07:00
trace	Merge branch 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2010-09-10 07:31:24 -07:00
.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	fanotify: use both marks when possible	2010-07-28 10:18:55 -04:00
audit_watch.c	Revert "fsnotify: store struct file not struct path"	2010-08-12 14:23:04 -07:00
audit.c	Merge branch 'for-linus' of git://git.infradead.org/users/eparis/notify	2010-08-10 11:39:13 -07:00
audit.h	Audit: split audit watch Kconfig	2010-07-28 09:58:19 -04:00
auditfilter.c	audit: do not get and put just to free a watch	2010-07-28 09:58:17 -04:00
auditsc.c	vfs: add helpers to get root and pwd	2010-08-11 00:28:20 -04:00
backtracetest.c
bounds.c	kbuild: move bounds.h to include/generated	2009-12-12 13:08:14 +01:00
capability.c	sched: Remove remaining USER_SCHED code	2010-04-02 20:12:00 +02:00
cgroup_freezer.c	Freezer / cgroup freezer: Update stale locking comments	2010-05-10 23:18:47 +02:00
cgroup.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
compat.c	compat: Make compat_alloc_user_space() incorporate the access_ok()	2010-09-14 16:08:45 -07:00
configs.c
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	Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2010-08-06 09:39:22 -07:00
cred.c	Add a dummy printk function for the maintenance of unused printks	2010-08-12 09:51:35 -07:00
delayacct.c
dma.c
early_res.c	kmemleak: Add support for NO_BOOTMEM configurations	2010-07-19 11:54:15 +01:00
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	Fix unprotected access to task credentials in waitid()	2010-08-17 18:07:43 -07:00
extable.c
fork.c	rmap: fix walk during fork	2010-09-22 17:22:39 -07:00
freezer.c
futex_compat.c	futex: Protect pid lookup in compat code with RCU	2009-12-09 14:22:14 +01:00
futex.c	futex: futex_find_get_task remove credentails check	2010-06-30 15:43:44 -07:00
groups.c	kernel/groups.c: fix integer overflow in groups_search	2010-09-09 18:57:24 -07:00
hrtimer.c	gcc-4.6: kernel/*: Fix unused but set warnings	2010-09-05 14:36:58 +02:00
hung_task.c	softlockup: Fix hung_task_check_count sysctl	2009-11-27 06:21:57 +01:00
hw_breakpoint.c	hw breakpoints: Fix pid namespace bug	2010-09-17 04:42:59 +02:00
itimer.c
kallsyms.c	kdb: core for kgdb back end (2 of 2)	2010-05-20 21:04:21 -05:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks	mutex: Better control mutex adaptive spinning config	2009-12-03 11:50:11 +01:00
Kconfig.preempt
kexec.c	kexec: return -EFAULT on copy_to_user() failures	2010-08-11 08:59:22 -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	kprobes: Move enable/disable_kprobe() out from debugfs code	2010-05-08 18:08:30 +02:00
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	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
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	sched_clock: Add local_clock() API and improve documentation	2010-06-09 10:34:49 +02:00
Makefile	rcu: Add a TINY_PREEMPT_RCU	2010-08-20 08:55:00 -07:00
module.c	modules: Fix module_bug_list list corruption race	2010-10-05 11:29:27 -07:00
mutex-debug.c
mutex-debug.h	locking: Implement new raw_spinlock	2009-12-14 23:55:32 +01:00
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
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: Fix CPU hotplug	2010-09-09 20:38:52 +02:00
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 QoS: Correct pr_debug() misuse and improve parameter checks	2010-09-11 00:53:05 +02:00
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	gcc-4.6: printk: use stable variable to dump kmsg buffer	2010-08-09 20:45:06 -07:00
profile.c	numa: in-kernel profiling: use cpu_to_mem() for per cpu allocations	2010-05-27 09:12:57 -07:00
ptrace.c	ptrace: optimize exit_ptrace() for the likely case	2010-08-11 08:59:19 -07:00
range.c	kernel/range: remove unused definition of ARRAY_SIZE()	2010-08-09 20:45:06 -07:00
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: Distinguish between boosting and boosted	2010-11-29 22:01:56 -08:00
rcutiny.c	rcu: add tracing for TINY_RCU and TINY_PREEMPT_RCU	2010-11-29 22:01:55 -08:00
rcutorture.c	rcu: add priority-inversion testing to rcutorture	2010-10-07 10:41:08 -07:00
rcutree_plugin.h	rcu: fix race condition in synchronize_sched_expedited()	2010-11-29 22:02:00 -08:00
rcutree_trace.c	rcu,cleanup: simplify the code when cpu is dying	2010-11-29 22:01:58 -08:00
rcutree.c	rcu: update documentation/comments for Lai's adoption patch	2010-11-29 22:01:59 -08:00
rcutree.h	rcu,cleanup: simplify the code when cpu is dying	2010-11-29 22:01:58 -08:00
relay.c	kernel/: convert cpu notifier to return encapsulate errno value	2010-05-27 09:12:48 -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	resource: shared I/O region support	2010-05-11 12:01:10 -07:00
rtmutex_common.h
rtmutex-debug.c	sched: Convert pi_lock to raw_spinlock	2009-12-14 23:55:33 +01:00
rtmutex-debug.h
rtmutex-tester.c
rtmutex.c	rtmutes: Convert rtmutex.lock to raw_spinlock	2009-12-14 23:55:33 +01:00
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: suppress RCU lockdep splat in task_fork_fair	2010-10-07 10:40:50 -07:00
sched_features.h	sched: Remove ASYM_GRAN feature	2010-03-11 18:32:53 +01:00
sched_idletask.c	sched: Cure load average vs NO_HZ woes	2010-04-23 11:02:02 +02:00
sched_rt.c	sched: task_tick_rt: Remove the obsolete ->signal != NULL check	2010-06-18 10:46:56 +02:00
sched_stats.h	sched: Remove the obsolete exit_state/signal hacks	2010-06-18 10:46:56 +02:00
sched.c	rcu,cleanup: move synchronize_sched_expedited() out of sched.c	2010-11-29 22:01:58 -08:00
seccomp.c
semaphore.c
signal.c	CRED: Fix RCU warning due to previous patch fixing __task_cred()'s checks	2010-08-04 11:17:10 -07:00
smp.c	generic-ipi: Fix deadlock in __smp_call_function_single	2010-09-10 16:48:40 +02:00
softirq.c	kernel/: fix BUG_ON checks for cpu notifier callbacks direct call	2010-06-04 15:21:45 -07:00
spinlock.c	locking: Cleanup the name space completely	2009-12-14 23:55:33 +01:00
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: struct cpu_stopper, remove alignment padding on 64 bits	2010-08-09 20:45:06 -07:00
sys_ni.c	fanotify: sys_fanotify_mark declartion	2010-07-28 09:58:55 -04:00
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	ipv4 05/05: add sysctl to accept packets with local source addresses	2009-12-03 12:14:38 -08:00
sysctl.c	gcc-4.6: kernel/*: Fix unused but set warnings	2010-09-05 14:36:58 +02:00
taskstats.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
test_kprobes.c
time.c	time: Kill off CONFIG_GENERIC_TIME	2010-07-27 12:40:54 +02:00
timeconst.pl
timer.c	kernel/timer.c: fix kernel-doc function parameter warning	2010-08-10 15:33:09 -07:00
tracepoint.c	tracing: Let tracepoints have data passed to tracepoint callbacks	2010-05-14 09:50:34 -04:00
tsacct.c	mm: clean up mm_counter	2010-03-06 11:26:23 -08:00
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	core: Clean up user return notifers use of per_cpu	2009-12-02 10:22:59 +01:00
user.c	sched: Remove a stale comment	2010-05-10 08:48:39 +02:00
utsname_sysctl.c
utsname.c
wait.c
watchdog.c	lockup_detector: Sync touch_*_watchdog back to old semantics	2010-09-01 10:02:28 +02:00
workqueue_sched.h	workqueue: implement concurrency managed dynamic worker pool	2010-06-29 10:07:14 +02:00
workqueue.c	workqueue: add documentation	2010-09-13 10:26:52 +02:00