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Paul E. McKenney 1924bcb025 rcu: Avoid counter wrap in synchronize_sched_expedited() 
There is a counter scheme similar to ticket locking that
synchronize_sched_expedited() uses to service multiple concurrent
callers with the same expedited grace period.  Upon entry, a
sync_sched_expedited_started variable is atomically incremented,
and upon completion of a expedited grace period a separate
sync_sched_expedited_done variable is atomically incremented.

However, if a synchronize_sched_expedited() is delayed while
in try_stop_cpus(), concurrent invocations will increment the
sync_sched_expedited_started counter, which will eventually overflow.
If the original synchronize_sched_expedited() resumes execution just
as the counter overflows, a concurrent invocation could incorrectly
conclude that an expedited grace period elapsed in zero time, which
would be bad.  One could rely on counter size to prevent this from
happening in practice, but the goal is to formally validate this
code, so it needs to be fixed anyway.

This commit therefore checks the gap between the two counters before
incrementing sync_sched_expedited_started, and if the gap is too
large, does a normal grace period instead.  Overflow is thus only
possible if there are more than about 3.5 billion threads on 32-bit
systems, which can be excluded until such time as task_struct fits
into a single byte and 4G/4G patches are accepted into mainline.
It is also easy to encode this limitation into mechanical theorem
provers.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 		2012-11-08 11:50:12 -08:00
..
debug KGDB/KDB fixes and cleanups 2012-10-13 11:16:58 +09:00
events Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-10-13 10:20:11 +09:00
gcov gcov: disable CONSTRUCTORS for UML 2011-07-26 16:49:45 -07:00
irq irqdomain: augment add_simple() to allocate descs 2012-10-10 08:57:26 +02:00
power Merge branch 'pm-qos' 2012-09-17 20:25:51 +02:00
sched Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-10-12 22:13:05 +09:00
time Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-10-12 22:17:48 +09:00
trace Merge branch 'virtio-next' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux 2012-10-07 21:04:56 +09:00
.gitignore
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Kconfig.freezer
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Kconfig.hz
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Kconfig.locks locking: Adjust spin lock inlining Kconfig options 2012-09-13 17:56:13 +02:00
Kconfig.preempt locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
Makefile Merge branch 'modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux 2012-10-14 13:39:34 -07:00
acct.c vfs: make path_openat take a struct filename pointer 2012-10-12 20:15:09 -04:00
async.c [SCSI] async: make async_synchronize_full() flush all work regardless of domain 2012-07-20 09:07:37 +01:00
audit.c fs: handle failed audit_log_start properly 2012-10-09 23:33:37 -04:00
audit.h audit: optimize audit_compare_dname_path 2012-10-12 00:32:02 -04:00
audit_tree.c audit: clean up refcounting in audit-tree 2012-08-15 12:55:22 +02:00
audit_watch.c audit: optimize audit_compare_dname_path 2012-10-12 00:32:02 -04:00
auditfilter.c audit: optimize audit_compare_dname_path 2012-10-12 00:32:02 -04:00
auditsc.c audit: make audit_inode take struct filename 2012-10-12 20:15:09 -04:00
backtracetest.c
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bounds.c
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capability.c userns: Teach inode_capable to understand inodes whose uids map to other namespaces. 2012-05-15 14:59:24 -07:00
cgroup.c Merge branch 'for-3.7-hierarchy' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2012-10-02 10:52:28 -07:00
cgroup_freezer.c cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them 2012-09-14 12:01:16 -07:00
compat.c new helper: sigsuspend() 2012-05-21 23:52:30 -04:00
configs.c kernel/configs.c: include MODULE_*() when CONFIG_IKCONFIG_PROC=n 2011-07-25 20:57:15 -07:00
cpu.c CPU hotplug, debug: detect imbalance between get_online_cpus() and put_online_cpus() 2012-10-09 16:22:15 +09:00
cpu_pm.c kernel/cpu_pm.c: fix various typos 2012-05-31 17:49:27 -07:00
cpuset.c cpusets: Remove/update outdated comments 2012-07-24 13:53:28 +02:00
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 userns: Make credential debugging user namespace safe. 2012-08-23 22:54:18 -07:00
delayacct.c KVM: Steal time implementation 2011-07-14 12:59:14 +03:00
dma.c Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
elfcore.c
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exec_domain.c
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exit.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-10-02 20:25:04 -07:00
extable.c extable: Skip sorting if sorted at build time. 2012-04-19 15:06:55 -07:00
fork.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal 2012-10-10 12:02:25 +09:00
freezer.c PM / Freezer: Remove references to TIF_FREEZE in comments 2012-03-04 23:08:54 +01:00
futex.c futex: Forbid uaddr == uaddr2 in futex_wait_requeue_pi() 2012-07-24 16:02:57 +02:00
futex_compat.c futex: Mark get_robust_list as deprecated 2012-03-29 11:37:17 +02:00
groups.c userns: Convert in_group_p and in_egroup_p to use kgid_t 2012-05-03 03:29:33 -07:00
hrtimer.c hrtimer: Update hrtimer base offsets each hrtimer_interrupt 2012-07-11 23:34:39 +02:00
hung_task.c hung task debugging: Inject NMI when hung and going to panic 2012-04-25 12:39:25 +02:00
irq_work.c irq_work: fix compile failure on tile from missing include 2012-04-13 13:15:16 -04:00
itimer.c itimer: Use printk_once instead of WARN_ONCE 2012-04-10 11:00:30 +02:00
jump_label.c jump_label: Export jump_label_rate_limit() 2012-08-06 19:00:35 +03:00
kallsyms.c vsprintf: fix %ps on non symbols when using kallsyms 2012-05-29 16:22:32 -07:00
kcmp.c syscalls, x86: add __NR_kcmp syscall 2012-05-31 17:49:32 -07:00
kexec.c kdump: remove unneeded include 2012-10-06 03:05:19 +09:00
kfifo.c [media] kernel:kfifo: export __kfifo_max_r symbol 2012-04-11 18:24:37 -03:00
kmod.c infrastructure for saner ret_from_kernel_thread semantics 2012-10-12 13:35:07 -04:00
kprobes.c kprobes/x86: Fix to support jprobes on ftrace-based kprobe 2012-09-13 22:52:11 -04:00
ksysfs.c kernel: ksysfs.c is implicitly using stat.h 2011-10-31 09:20:13 -04:00
kthread.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal 2012-10-13 10:05:52 +09:00
latencytop.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lglock.c brlocks/lglocks: turn into functions 2012-05-29 23:28:41 -04:00
lockdep.c lockdep: Check if nested lock is actually held 2012-09-13 17:00:44 +02:00
lockdep_internals.h
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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
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modsign_pubkey.c MODSIGN: Provide module signing public keys to the kernel 2012-10-10 20:01:22 +10:30
module-internal.h MODSIGN: Move the magic string to the end of a module and eliminate the search 2012-10-19 17:30:40 -07:00
module.c MODSIGN: Move the magic string to the end of a module and eliminate the search 2012-10-19 17:30:40 -07:00
module_signing.c MODSIGN: Move the magic string to the end of a module and eliminate the search 2012-10-19 17:30:40 -07:00
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 sched/rt: Use schedule_preempt_disabled() 2012-03-01 10:28:03 +01:00
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 padata: Fix cpu hotplug 2012-03-29 19:52:46 +08:00
panic.c panic: fix a possible deadlock in panic() 2012-07-30 17:25:13 -07:00
params.c params: replace printk(KERN_<LVL>...) with pr_<lvl>(...) 2012-05-04 17:28:18 -07:00
pid.c net ip6 flowlabel: Make owner a union of struct pid * and kuid_t 2012-08-14 21:49:25 -07:00
pid_namespace.c pidns: remove recursion from free_pid_ns() 2012-10-19 14:07:47 -07:00
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 printk: Fix scheduling-while-atomic problem in console_cpu_notify() 2012-10-16 18:17:44 -07:00
profile.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
ptrace.c ptrace: mark __ptrace_may_access() static 2012-08-03 14:47:17 +10:00
range.c range: fix bogus misuse of module.h to get printk() 2011-10-31 09:20:11 -04:00
rcu.h rcu: Allow nesting of rcu_idle_enter() and rcu_idle_exit() 2012-02-21 09:06:12 -08:00
rcupdate.c rcu: Add PROVE_RCU_DELAY to provoke difficult races 2012-09-23 07:42:49 -07:00
rcutiny.c rcu: Move TINY_RCU quiescent state out of extended quiescent state 2012-09-23 07:42:52 -07:00
rcutiny_plugin.h rcu: Move TINY_PREEMPT_RCU away from raw_local_irq_save() 2012-09-23 07:42:51 -07:00
rcutorture.c rcu: Make rcutorture give diagnostics if CPU offline fails 2012-10-23 14:46:47 -07:00
rcutree.c rcu: Avoid counter wrap in synchronize_sched_expedited() 2012-11-08 11:50:12 -08:00
rcutree.h rcu: Rename ->onofflock to ->orphan_lock 2012-11-08 11:50:11 -08:00
rcutree_plugin.h rcu: Rename ->onofflock to ->orphan_lock 2012-11-08 11:50:11 -08:00
rcutree_trace.c Merge remote-tracking branch 'tip/smp/hotplug' into next.2012.09.25b 2012-09-25 10:01:45 -07:00
relay.c splice: fix racy pipe->buffers uses 2012-06-13 21:16:42 +02:00
res_counter.c rescounters: add res_counter_uncharge_until() 2012-05-29 16:22:27 -07:00
resource.c kernel/resource.c: fix stack overflow in __reserve_region_with_split() 2012-10-06 03:05:31 +09:00
rtmutex-debug.c lockdep, rtmutex, bug: Show taint flags on error 2011-12-06 08:16:49 +01:00
rtmutex-debug.h
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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
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rtmutex_common.h
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rwsem.c Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
seccomp.c seccomp: fix build warnings when there is no CONFIG_SECCOMP_FILTER 2012-04-18 12:24:52 +10:00
semaphore.c semaphore: fix improper comment reference to mutex 2012-04-05 17:15:55 -07:00
signal.c coredump: pass siginfo_t* to do_coredump() and below, not merely signr 2012-10-06 03:05:16 +09:00
smp.c smp: Remove ipi_call_lock[_irq]()/ipi_call_unlock[_irq]() 2012-06-05 17:27:14 +02:00
smpboot.c hotplug: Fix UP bug in smpboot hotplug code 2012-08-13 17:01:07 +02:00
smpboot.h smpboot: Provide infrastructure for percpu hotplug threads 2012-08-13 17:01:07 +02:00
softirq.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-10-01 10:43:39 -07:00
spinlock.c locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage 2012-03-23 13:18:57 +01:00
srcu.c workqueue: deprecate system_nrt[_freezable]_wq 2012-08-20 14:51:24 -07:00
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 use clamp_t in UNAME26 fix 2012-10-19 18:51:17 -07:00
sys_ni.c syscalls, x86: add __NR_kcmp syscall 2012-05-31 17:49:32 -07:00
sysctl.c Kconfig: clean up the "#if defined(arch)" list for exception-trace sysctl entry 2012-10-09 16:22:14 +09:00
sysctl_binary.c mm: prepare for removal of obsolete /proc/sys/vm/nr_pdflush_threads 2012-07-31 18:42:40 -07:00
task_work.c task_work: task_work_add() should not succeed after exit_task_work() 2012-09-13 16:47:34 +02:00
taskstats.c taskstats: cgroupstats_user_cmd() may leak on error 2012-10-06 03:05:31 +09:00
test_kprobes.c
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time.c time: Move update_vsyscall definitions to timekeeper_internal.h 2012-09-24 12:38:06 -04:00
timeconst.pl
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timer.c timers: Fix endless looping between cascade() and internal_add_timer() 2012-10-09 21:27:14 +02:00
tracepoint.c static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]() 2012-02-24 10:05:59 +01:00
tsacct.c userns: Convert taskstats to handle the user and pid namespaces. 2012-09-18 01:01:32 -07:00
uid16.c userns: Convert setting and getting uid and gid system calls to use kuid and kgid 2012-05-03 03:28:41 -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-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 userns: Add kprojid_t and associated infrastructure in projid.h 2012-09-18 01:01:37 -07:00
user_namespace.c userns: Add kprojid_t and associated infrastructure in projid.h 2012-09-18 01:01:37 -07:00
utsname.c userns: Use cred->user_ns instead of cred->user->user_ns 2012-04-07 16:55:51 -07:00
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 lockdep/waitqueues: Add better annotation 2011-12-21 10:07:39 +01:00
watchdog.c watchdog: Use hotplug thread infrastructure 2012-08-13 17:01:07 +02:00
workqueue.c Merge branch 'for-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2012-10-02 09:54:49 -07:00
workqueue_sched.h
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