Paul E. McKenney 26cdfedf6a rcu: Reject memory-order-induced stall-warning false positives ... If a system is idle from an RCU perspective for longer than specified by CONFIG_RCU_CPU_STALL_TIMEOUT, and if one CPU starts a grace period just as a second checks for CPU stalls, and if this second CPU happens to see the old value of rsp->jiffies_stall, it will incorrectly report a CPU stall. This is quite rare, but apparently occurs deterministically on systems with about 6TB of memory. This commit therefore orders accesses to the data used to determine whether or not a CPU stall is in progress. Grace-period initialization and cleanup first increments rsp->completed to mark the end of the previous grace period, then records the current jiffies in rsp->gp_start, then records the jiffies at which a stall can be expected to occur in rsp->jiffies_stall, and finally increments rsp->gpnum to mark the start of the new grace period. Now, this ordering by itself does not prevent false positives. For example, if grace-period initialization was delayed between recording rsp->gp_start and rsp->jiffies_stall, the CPU stall warning code might still see an old value of rsp->jiffies_stall. Therefore, this commit also orders the CPU stall warning accesses as well, loading rsp->gpnum and jiffies, then rsp->jiffies_stall, then rsp->gp_start, and finally rsp->completed. This ordering means that the false-positive scenario in the previous paragraph would result in rsp->completed being greater than or equal to rsp->gpnum, which is never valid for a CPU stall, allowing the false positive to be rejected. Furthermore, any fetch that gets an old value of rsp->jiffies_stall must also get an old value of rsp->gpnum, which will again be rejected by the comparison of rsp->gpnum and rsp->completed. Situations where rsp->gp_start is later than rsp->jiffies_stall are also rejected, as are situations where jiffies is less than rsp->jiffies_stall. Although use of unsynchronized accesses means that there are likely still some false-positive scenarios (synchronization has proven to be a very bad idea on large systems), this should get rid of a large class of these scenarios. Reported-by: Fabian Herschel <fabian.herschel@suse.com> Reported-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Tested-by: Jochen Striepe <jochen@tolot.escape.de>		2013-09-23 09:15:30 -07:00
..
cpu	idle: Enable interrupts in the weak arch_cpu_idle() implementation	2013-06-14 23:01:05 +02:00
debug	kgdb/sysrq: fix inconstistent help message of sysrq key	2013-04-30 17:04:10 -07:00
events	uprobes: Fix utask->depth accounting in handle_trampoline()	2013-09-12 08:00:55 +02:00
gcov	kernel: replace strict_strto*() with kstrto*()	2013-09-12 15:38:03 -07:00
irq	Remove GENERIC_HARDIRQ config option	2013-09-13 15:09:52 +02:00
power	ACPI and power management fixes for 3.12-rc1	2013-09-12 11:22:45 -07:00
printk	TTY/Serial driver patches for 3.12-rc1	2013-09-03 11:38:36 -07:00
sched	Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2013-09-12 10:44:13 -07:00
time	Merge branch 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2013-09-04 09:36:54 -07:00
trace	Not much changes for the 3.12 merge window. The major tracing changes	2013-09-09 14:42:15 -07:00
.gitignore	kernel/hz.bc: ignore.	2013-04-22 07:09:06 -07:00
acct.c	fs: Fix hang with BSD accounting on frozen filesystem	2013-05-04 14:57:58 -04:00
async.c	async: rename and redefine async_func_ptr	2013-03-12 13:59:14 -07:00
audit.c	audit: wait_for_auditd() should use TASK_UNINTERRUPTIBLE	2013-06-12 16:29:45 -07:00
audit.h	audit: fix mq_open and mq_unlink to add the MQ root as a hidden parent audit_names record	2013-07-09 10:33:19 -07:00
audit_tree.c	kernel/audit_tree.c:audit_add_tree_rule(): protect `rule' from kill_rules()	2013-06-12 16:29:46 -07:00
audit_watch.c
auditfilter.c	audit: Fix decimal constant description	2013-07-09 10:33:19 -07:00
auditsc.c	audit: fix mq_open and mq_unlink to add the MQ root as a hidden parent audit_names record	2013-07-09 10:33:19 -07:00
backtracetest.c
bounds.c
capability.c	xfs: update for v3.12-rc1	2013-09-09 11:19:09 -07:00
cgroup.c	Kill indirect include of file.h from eventfd.h, use fdget() in cgroup.c	2013-09-07 19:54:57 -04:00
cgroup_freezer.c	cgroup: make css_for_each_descendant() and friends include the origin css in the iteration	2013-08-08 20:11:27 -04:00
compat.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal	2013-05-01 07:21:43 -07:00
configs.c	proc: Supply PDE attribute setting accessor functions	2013-05-01 17:29:18 -04:00
context_tracking.c	context_tracking: User/kernel broundary cross trace events	2013-08-14 17:14:48 +02:00
cpu.c	ACPI / processor: Acquire writer lock to update CPU maps	2013-08-13 12:20:16 +02:00
cpu_pm.c
cpuset.c	Merge branch 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2013-09-03 18:25:03 -07:00
crash_dump.c
cred.c
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c	ptrace: revert "Prepare to fix racy accesses on task breakpoints"	2013-07-09 10:33:26 -07:00
extable.c	extable: skip sorting if the table is empty	2013-09-11 15:58:25 -07:00
fork.c	Merge git://git.kvack.org/~bcrl/aio-next	2013-09-13 10:55:58 -07:00
freezer.c	freezer: set PF_SUSPEND_TASK flag on tasks that call freeze_processes	2013-07-30 14:05:06 +02:00
futex.c	futex: Use freezable blocking call	2013-06-25 23:11:19 +02:00
futex_compat.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal	2013-02-23 18:50:11 -08:00
groups.c	userns: Kill nsown_capable it makes the wrong thing easy	2013-08-30 23:44:11 -07:00
hrtimer.c	kernel: delete __cpuinit usage from all core kernel files	2013-07-14 19:36:59 -04:00
hung_task.c	hung_task debugging: Print more info when reporting the problem	2013-08-02 11:02:42 +02:00
irq_work.c
itimer.c
jump_label.c	jump_label: Split jumplabel ratelimit	2013-08-09 07:53:54 -07:00
kallsyms.c	kernel: kallsyms: memory override issue, need check destination buffer length	2013-04-15 15:17:26 +09:30
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks	locking: Fix copy/paste errors of "ARCH_INLINE_*_UNLOCK_BH"	2013-05-28 08:50:00 +02:00
Kconfig.preempt
kexec.c	kexec: remove unnecessary return	2013-09-11 15:59:10 -07:00
kmod.c	usermodehelper: kill the sub_info->path[0] check	2013-07-03 16:08:02 -07:00
kprobes.c	kprobes: allow to specify custom allocator for insn caches	2013-09-11 15:58:52 -07:00
ksysfs.c	kernel: replace strict_strto*() with kstrto*()	2013-09-12 15:38:03 -07:00
kthread.c	kthread: implement probe_kthread_data()	2013-04-30 17:04:02 -07:00
latencytop.c
lglock.c	lglock: Update lockdep annotations to report recursive local locks	2013-07-12 13:51:19 +02:00
lockdep.c	lockdep: remove task argument from debug_check_no_locks_held	2013-05-12 14:16:21 +02:00
lockdep_internals.h
lockdep_proc.c
lockdep_states.h
Makefile	Remove GENERIC_HARDIRQ config option	2013-09-13 15:09:52 +02:00
modsign_certificate.S	CONFIG_SYMBOL_PREFIX: cleanup.	2013-03-15 15:09:43 +10:30
modsign_pubkey.c	kernel/modsign_pubkey.c: fix init const for module signing code	2013-09-11 15:58:21 -07:00
module-internal.h
module.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2013-09-05 08:50:26 -07:00
module_signing.c
mutex-debug.c
mutex-debug.h
mutex.c	Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2013-09-04 08:18:19 -07:00
mutex.h
notifier.c
nsproxy.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2013-09-07 14:35:32 -07:00
padata.c	padata - Register hotcpu notifier after initialization	2013-08-29 14:37:59 +10:00
panic.c	panic: call panic handlers before kmsg_dump	2013-09-11 15:59:30 -07:00
params.c	kernel: replace strict_strto*() with kstrto*()	2013-09-12 15:38:03 -07:00
pid.c	pidns: Fix hang in zap_pid_ns_processes by sending a potentially extra wakeup	2013-08-30 17:30:37 -07:00
pid_namespace.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2013-09-07 14:35:32 -07:00
posix-cpu-timers.c	posix_timers: fix racy timer delta caching on task exit	2013-07-03 16:54:42 +02:00
posix-timers.c	posix-timers: Remove unused variable	2013-04-18 12:51:19 +02:00
profile.c	kernel: delete __cpuinit usage from all core kernel files	2013-07-14 19:36:59 -04:00
ptrace.c	__ptrace_may_access() should not deny sub-threads	2013-09-11 15:59:01 -07:00
range.c	range: Do not add new blank slot with add_range_with_merge	2013-06-18 11:32:10 -05:00
rcu.h	rcu: Make call_rcu() leak callbacks for debug-object errors	2013-08-18 17:40:03 -07:00
rcupdate.c	rcu: Convert local functions to static	2013-09-23 09:12:31 -07:00
rcutiny.c	rcu: Add const annotation to char * for RCU tracepoints and functions	2013-07-29 17:07:49 -04:00
rcutiny_plugin.h	rcu: Add const annotation to char * for RCU tracepoints and functions	2013-07-29 17:07:49 -04:00
rcutorture.c	rcu: Make rcutorture emit online failures if verbose	2013-08-20 11:38:45 -07:00
rcutree.c	rcu: Reject memory-order-induced stall-warning false positives	2013-09-23 09:15:30 -07:00
rcutree.h	nohz_full: Force RCU's grace-period kthreads onto timekeeping CPU	2013-08-31 14:44:02 -07:00
rcutree_plugin.h	rcu: Replace __get_cpu_var() uses	2013-09-23 09:15:22 -07:00
rcutree_trace.c	rcutrace: single_open() leaks	2013-05-05 00:16:35 -04:00
reboot.c	reboot: move arch/x86 reboot= handling to generic kernel	2013-07-09 10:33:29 -07:00
relay.c	kernel: delete __cpuinit usage from all core kernel files	2013-07-14 19:36:59 -04:00
res_counter.c	memcg: reduce function dereference	2013-09-12 15:38:02 -07:00
resource.c	kernel/resource.c: remove the unneeded assignment in function __find_resource	2013-07-03 16:08:06 -07:00
rtmutex-debug.c	sched/rt: Move rt specific bits into new header file	2013-02-07 20:51:08 +01:00
rtmutex-debug.h
rtmutex-tester.c	locking/rtmutex/tester: Set correct permissions on sysfs files	2013-04-10 14:48:37 +02:00
rtmutex.c	rtmutex: Document rt_mutex_adjust_prio_chain()	2013-05-28 09:23:52 +02:00
rtmutex.h
rtmutex_common.h
rwsem.c	Revert "rw_semaphore: remove up/down_read_non_owner"	2013-03-23 15:53:52 -07:00
seccomp.c	seccomp: allow BPF_XOR based ALU instructions.	2013-03-26 11:07:19 +11:00
semaphore.c	semaphore: use `bool' type for semaphore_waiter's up	2013-04-30 17:04:08 -07:00
signal.c	kernel-wide: fix missing validations on __get/__put/__copy_to/__copy_from_user()	2013-09-11 15:58:18 -07:00
smp.c	kernel/smp.c: quit unconditionally enabling irqs in on_each_cpu_mask().	2013-09-11 15:58:25 -07:00
smpboot.c	kernel: delete __cpuinit usage from all core kernel files	2013-07-14 19:36:59 -04:00
smpboot.h
softirq.c	Remove GENERIC_HARDIRQ config option	2013-09-13 15:09:52 +02:00
spinlock.c	kernel/spinlock.c: add default arch_*_relax definitions for GENERIC_LOCKBREAK	2013-09-11 15:58:21 -07:00
srcu.c	srcu: use ACCESS_ONCE() to access sp->completed in srcu_read_lock()	2013-02-07 15:19:36 -08:00
stacktrace.c
stop_machine.c	stop_machine: Mark per cpu stopper enabled early	2013-02-26 22:25:17 +01:00
sys.c	userns: Kill nsown_capable it makes the wrong thing easy	2013-08-30 23:44:11 -07:00
sys_ni.c	unify compat fanotify_mark(2), switch to COMPAT_SYSCALL_DEFINE	2013-05-09 13:46:38 -04:00
sysctl.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2013-09-12 15:01:38 -07:00
sysctl_binary.c	kernel: remove unnecessary head file	2013-06-26 18:01:46 +09:00
task_work.c	task_work: documentation	2013-09-11 15:58:27 -07:00
taskstats.c
test_kprobes.c	kernel/: rename random32() to prandom_u32()	2013-04-29 18:28:42 -07:00
time.c	sched: Rename sched.c as sched/core.c in comments and Documentation	2013-06-19 12:58:42 +02:00
timeconst.bc	kernel: Replace timeconst.pl with a bc script	2013-02-16 23:17:25 +01:00
timer.c	kernel: delete __cpuinit usage from all core kernel files	2013-07-14 19:36:59 -04:00
tracepoint.c	Tracing updates for Linux 3.10	2013-04-29 13:55:38 -07:00
tsacct.c
uid16.c	userns: Kill nsown_capable it makes the wrong thing easy	2013-08-30 23:44:11 -07:00
up.c	smp.h: move !SMP version of on_each_cpu() out-of-line	2013-09-11 15:58:25 -07:00
user-return-notifier.c	hlist: drop the node parameter from iterators	2013-02-27 19:10:24 -08:00
user.c	userns: Better restrictions on when proc and sysfs can be mounted	2013-08-26 19:17:03 -07:00
user_namespace.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2013-09-07 14:35:32 -07:00
utsname.c	userns: Kill nsown_capable it makes the wrong thing easy	2013-08-30 23:44:11 -07:00
utsname_sysctl.c	kernel/utsname_sysctl.c: put get/get_uts() into CONFIG_PROC_SYSCTL code block	2013-02-27 19:10:22 -08:00
wait.c	kernel: fix new kernel-doc warning in wait.c	2013-08-19 09:08:54 -07:00
watchdog.c	watchdog: Make it work under full dynticks	2013-07-30 22:29:15 +02:00
workqueue.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial	2013-09-06 09:36:28 -07:00
workqueue_internal.h	sched: Rename sched.c as sched/core.c in comments and Documentation	2013-06-19 12:58:42 +02:00