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313517fc44
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Paul E. McKenney 313517fc44 rcu: Make expedited GPs correctly handle hardware CPU insertion 
The update of the ->expmaskinitnext and of ->ncpus are unsynchronized,
with the value of ->ncpus being incremented long before the corresponding
->expmaskinitnext mask is updated.  If an RCU expedited grace period
sees ->ncpus change, it will update the ->expmaskinit masks from the new
->expmaskinitnext masks.  But it is possible that ->ncpus has already
been updated, but the ->expmaskinitnext masks still have their old values.
For the current expedited grace period, no harm done.  The CPU could not
have been online before the grace period started, so there is no need to
wait for its non-existent pre-existing readers.

But the next RCU expedited grace period is in a world of hurt.  The value
of ->ncpus has already been updated, so this grace period will assume
that the ->expmaskinitnext masks have not changed.  But they have, and
they won't be taken into account until the next never-been-online CPU
comes online.  This means that RCU will be ignoring some CPUs that it
should be paying attention to.

The solution is to update ->ncpus and ->expmaskinitnext while holding
the ->lock for the rcu_node structure containing the ->expmaskinitnext
mask.  Because smp_store_release() is now used to update ->ncpus and
smp_load_acquire() is now used to locklessly read it, if the expedited
grace period sees ->ncpus change, then the updating CPU has to
already be holding the corresponding ->lock.  Therefore, when the
expedited grace period later acquires that ->lock, it is guaranteed
to see the new value of ->expmaskinitnext.

On the other hand, if the expedited grace period loads ->ncpus just
before an update, earlier full memory barriers guarantee that
the incoming CPU isn't far enough along to be running any RCU readers.

This commit therefore makes the required change.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-07-25 13:04:45 -07:00
..
bpf Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-07-20 16:33:39 -07:00
cgroup mm, cpuset: always use seqlock when changing task's nodemask 2017-07-06 16:24:34 -07:00
configs config: android-base: disable CONFIG_NFSD and CONFIG_NFS_FS 2017-06-09 11:47:38 +02:00
debug sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
events Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-21 11:12:48 -07:00
gcov gcov: support GCC 7.1 2017-05-12 15:57:15 -07:00
irq genirq/PM: Properly pretend disabled state when force resuming interrupts 2017-07-17 22:32:20 +02:00
livepatch livepatch: Fix stacking of patches with respect to RCU 2017-06-20 10:42:19 +02:00
locking Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-21 11:11:23 -07:00
power More power management updates for v4.13-rc1 2017-07-10 15:16:21 -07:00
printk Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 2017-07-05 11:11:26 -07:00
rcu rcu: Make expedited GPs correctly handle hardware CPU insertion 2017-07-25 13:04:45 -07:00
sched Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-21 11:16:12 -07:00
time Merge branch 'timers-compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-05 15:34:35 -07:00
trace trace: fix the errors caused by incompatible type of RCU variables 2017-07-20 09:27:29 -04:00
.gitignore
acct.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
async.c async: Adjust system_state checks 2017-05-23 10:01:37 +02:00
audit_fsnotify.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-05-03 11:05:15 -07:00
audit_tree.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-05-03 11:05:15 -07:00
audit_watch.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-05-03 11:05:15 -07:00
audit.c Merge branch 'stable-4.13' of git://git.infradead.org/users/pcmoore/audit 2017-07-20 10:22:26 -07:00
audit.h audit: style fix 2017-06-12 18:07:43 -04:00
auditfilter.c audit: kernel generated netlink traffic should have a portid of 0 2017-05-02 10:16:05 -04:00
auditsc.c Merge branch 'stable-4.13' of git://git.infradead.org/users/pcmoore/audit 2017-07-05 11:24:05 -07:00
backtracetest.c
bounds.c
capability.c
compat.c Merge branch 'misc.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-06 20:57:13 -07:00
configs.c
context_tracking.c
cpu_pm.c
cpu.c rcu: Migrate callbacks earlier in the CPU-offline timeline 2017-07-25 13:03:43 -07:00
crash_core.c kdump: protect vmcoreinfo data under the crash memory 2017-07-12 16:26:00 -07:00
crash_dump.c
cred.c doc: ReSTify credentials.txt 2017-05-18 10:30:19 -06:00
delayacct.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
dma.c
elfcore.c
exec_domain.c
exit.c kernel/exit.c: avoid undefined behaviour when calling wait4() 2017-07-10 16:32:36 -07:00
extable.c lib/extable.c: use bsearch() library function in search_extable() 2017-07-10 16:32:35 -07:00
fork.c fork,random: use get_random_canary() to set tsk->stack_canary 2017-07-12 16:26:03 -07:00
freezer.c
futex_compat.c
futex.c Now that IPC and other changes have landed, enable manual markings for 2017-07-19 08:55:18 -07:00
groups.c kernel/groups.c: use sort library function 2017-07-10 16:32:34 -07:00
hung_task.c kernel/hung_task.c: defer showing held locks 2017-05-08 17:15:10 -07:00
irq_work.c
jump_label.c jump_label: Reorder hotplug lock and jump_label_lock 2017-05-26 10:10:45 +02:00
kallsyms.c kernel/kallsyms.c: replace all_var with IS_ENABLED(CONFIG_KALLSYMS_ALL) 2017-07-10 16:32:34 -07:00
kcmp.c kcmp: add KCMP_EPOLL_TFD mode to compare epoll target files 2017-07-12 16:26:01 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kcov: simplify interrupt check 2017-05-08 17:15:12 -07:00
kexec_core.c kdump: protect vmcoreinfo data under the crash memory 2017-07-12 16:26:00 -07:00
kexec_file.c kexec_file: adjust declaration of kexec_purgatory 2017-07-12 16:26:02 -07:00
kexec_internal.h kexec_file: adjust declaration of kexec_purgatory 2017-07-12 16:26:02 -07:00
kexec.c kdump: protect vmcoreinfo data under the crash memory 2017-07-12 16:26:00 -07:00
kmod.c kmod: throttle kmod thread limit 2017-07-14 15:05:13 -07:00
kprobes.c kprobes: Ensure that jprobe probepoints are at function entry 2017-07-08 11:05:35 +02:00
ksysfs.c kexec: move vmcoreinfo out of the kernel's .bss section 2017-07-12 16:25:59 -07:00
kthread.c cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups 2017-03-17 10:18:47 -04:00
latencytop.c sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h> 2017-03-02 08:42:39 +01:00
Makefile kernel/watchdog: split up config options 2017-07-12 16:26:02 -07:00
membarrier.c
memremap.c mm, memory_hotplug: replace for_device by want_memblock in arch_add_memory 2017-07-06 16:24:32 -07:00
module_signing.c
module-internal.h
module.c Modules updates for v4.13 2017-07-12 17:22:01 -07:00
notifier.c kernel/notifier.c: simplify expression 2017-02-24 17:46:56 -08:00
nsproxy.c perf: Add PERF_RECORD_NAMESPACES to include namespaces related info 2017-03-13 15:57:41 -03:00
padata.c padata: Avoid nested calls to cpus_read_lock() in pcrypt_init_padata() 2017-05-26 10:10:37 +02:00
panic.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
params.c boot/param: Move next_arg() function to lib/cmdline.c for later reuse 2017-04-18 10:37:13 +02:00
pid_namespace.c pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes 2017-05-13 17:26:01 -05:00
pid.c mm: update callers to use HASH_ZERO flag 2017-07-06 16:24:33 -07:00
profile.c sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h> 2017-03-02 08:42:39 +01:00
ptrace.c ptrace: Properly initialize ptracer_cred on fork 2017-05-23 07:40:44 -05:00
range.c
reboot.c
relay.c Merge branch 'work.splice' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-05-02 11:38:06 -07:00
resource.c
seccomp.c seccomp: Switch from atomic_t to recount_t 2017-06-26 09:24:00 -07:00
signal.c kernel/signal.c: avoid undefined behaviour in kill_something_info 2017-07-10 16:32:36 -07:00
smp.c smp, cpumask: Use non-atomic cpumask_{set,clear}_cpu() 2017-05-23 10:01:32 +02:00
smpboot.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
smpboot.h
softirq.c sched/core: Remove 'task' parameter and rename tsk_restore_flags() to current_restore_flags() 2017-04-11 09:06:32 +02:00
stacktrace.c stacktrace/x86: add function for detecting reliable stack traces 2017-03-08 09:18:02 +01:00
stop_machine.c stop_machine: Provide stop_machine_cpuslocked() 2017-05-26 10:10:36 +02:00
sys_ni.c
sys.c fix a braino in compat_sys_getrlimit() 2017-07-12 09:15:00 -07:00
sysctl_binary.c kernel/sysctl_binary.c: check name array length in deprecated_sysctl_warning() 2017-07-12 16:26:00 -07:00
sysctl.c kernel/watchdog: split up config options 2017-07-12 16:26:02 -07:00
task_work.c
taskstats.c taskstats: add e/u/stime for TGID command 2017-05-08 17:15:12 -07:00
test_kprobes.c
torture.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/clock.h> 2017-03-02 08:42:27 +01:00
tracepoint.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
tsacct.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
ucount.c ucount: Remove the atomicity from ucount->count 2017-03-06 15:26:37 -06:00
uid16.c sched/headers: Prepare to remove <linux/cred.h> inclusion from <linux/sched.h> 2017-03-02 08:42:31 +01:00
up.c
user_namespace.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/signal.h> 2017-03-02 08:42:29 +01:00
user-return-notifier.c
user.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/user.h> 2017-03-02 08:42:29 +01:00
utsname_sysctl.c sched/headers: Remove <linux/rwsem.h> from <linux/sched.h> 2017-03-03 01:45:36 +01:00
utsname.c sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h> 2017-03-02 08:42:38 +01:00
watchdog_hld.c kernel/watchdog: split up config options 2017-07-12 16:26:02 -07:00
watchdog.c kernel/watchdog.c: use better pr_fmt prefix 2017-07-14 15:05:13 -07:00
workqueue_internal.h
workqueue.c sched/wait: Rename wait_queue_t => wait_queue_entry_t 2017-06-20 12:18:27 +02:00