CPU hotplug: provide a generic helper to disable/enable CPU hotplug

There are instances in the kernel where we would like to disable CPU
hotplug (from sysfs) during some important operation.  Today the freezer
code depends on this and the code to do it was kinda tailor-made for that.

Restructure the code and make it generic enough to be useful for
other usecases too.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Robin Holt <holt@sgi.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Russ Anderson <rja@sgi.com>
Cc: Robin Holt <holt@sgi.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

shm-fix-null-pointer-deref-when-userspace-specifies-invalid-hugepage-size-fix

eliminate ugly 80-col tricks

Cc: Dave Jones <davej@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Li Zefan <lizfan@huawei.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Merge remote-tracking branch 'lzo-update/lzo-update'

Merge remote-tracking branch 'clk/clk-next'

Merge remote-tracking branch 'userns/for-next'

Merge remote-tracking branch 'pwm/for-next'

Merge remote-tracking branch 'tegra/for-next'

Merge remote-tracking branch 'samsung/for-next'

Merge remote-tracking branch 'renesas/next'

Merge remote-tracking branch 'mvebu/for-next'

Merge remote-tracking branch 'msm/for-next'

Merge remote-tracking branch 'imx-mxs/for-next'

Merge remote-tracking branch 'ep93xx/ep93xx-for-next'

Merge remote-tracking branch 'bcm2835/for-next'

Merge remote-tracking branch 'arm-soc/for-next'

Merge remote-tracking branch 'mailbox/dbx500-prcmu-mailbox'

Merge remote-tracking branch 'irqdomain/irqdomain/next'

Merge remote-tracking branch 'pinctrl/for-next'

Merge remote-tracking branch 'bcon/master'

Conflicts:
drivers/block/Kconfig

Merge remote-tracking branch 'char-misc/char-misc-next'

Merge remote-tracking branch 'staging/staging-next'

Conflicts:
drivers/staging/nvec/nvec_kbd.c

Merge remote-tracking branch 'usb/usb-next'

Merge remote-tracking branch 'tty/tty-next'

Merge remote-tracking branch 'driver-core/driver-core-next'

Conflicts:
drivers/base/cpu.c

Merge remote-tracking branch 'leds/for-next'

Merge remote-tracking branch 'regmap/for-next'

Merge remote-tracking branch 'workqueues/for-next'

Merge remote-tracking branch 'kvm-arm/kvm-arm-next'

Merge remote-tracking branch 'kvm/linux-next'

Conflicts:
arch/s390/include/asm/pgtable.h

Merge remote-tracking branch 'rcu/rcu/next'

Merge remote-tracking branch 'tip/auto-latest'

Merge remote-tracking branch 'spi-mb/for-next'

Merge remote-tracking branch 'watchdog/master'

Merge remote-tracking branch 'selinux/master'

Merge remote-tracking branch 'security/next'

Merge remote-tracking branch 'regulator/for-next'

Merge remote-tracking branch 'omap_dss2/for-next'

Merge remote-tracking branch 'mfd/master'

Conflicts:
drivers/mfd/intel_msic.c

Merge remote-tracking branch 'md/for-next'

Merge remote-tracking branch 'kgdb/kgdb-next'

Merge remote-tracking branch 'mmc/mmc-next'

Merge branch 'device-mapper/master'

Merge remote-tracking branch 'block/for-next'

Merge remote-tracking branch 'cgroup/for-next'

Merge remote-tracking branch 'input-mt/for-next'

Merge remote-tracking branch 'input/next'

Merge remote-tracking branch 'virtio/virtio-next'

Merge remote-tracking branch 'modules/modules-next'

Merge remote-tracking branch 'sound-asoc/for-next'

Merge remote-tracking branch 'sound/for-next'

Merge remote-tracking branch 'drm-intel/for-linux-next'

Merge remote-tracking branch 'crypto/master'

Merge remote-tracking branch 'l2-mtd/master'

Merge remote-tracking branch 'bluetooth/master'

Merge remote-tracking branch 'wireless-next/master'

Merge remote-tracking branch 'net-next/master'

Merge remote-tracking branch 'slave-dma/next'

Merge remote-tracking branch 'scsi/for-next'

Merge remote-tracking branch 'ubi/linux-next'

Merge remote-tracking branch 'thermal/next'

Merge remote-tracking branch 'cpuidle/cpuidle-next'

Conflicts:
drivers/acpi/processor_driver.c
drivers/base/power/qos.c

Merge remote-tracking branch 'idle/next'

Merge remote-tracking branch 'pm/linux-next'

Merge remote-tracking branch 'infiniband/for-next'

Merge remote-tracking branch 'libata/for-next'

Merge remote-tracking branch 'kbuild/for-next'

Merge remote-tracking branch 'v4l-dvb/master'

Merge remote-tracking branch 'hwmon-staging/hwmon-next'

Merge remote-tracking branch 'hid/for-next'

Merge remote-tracking branch 'pci/next'

Merge remote-tracking branch 'xfs/for-next'

Conflicts:
fs/xfs/xfs_attr_leaf.c

Merge remote-tracking branch 'ocfs2/linux-next'

Merge remote-tracking branch 'nfsd/nfsd-next'

Merge remote-tracking branch 'nfs/linux-next'

Merge remote-tracking branch 'logfs/master'

Merge remote-tracking branch 'jfs/jfs-next'

Merge remote-tracking branch 'gfs2/master'

Merge remote-tracking branch 'fuse/for-next'

Merge remote-tracking branch 'fscache/fscache'

Merge remote-tracking branch 'f2fs/dev'

Merge remote-tracking branch 'ecryptfs/next'

Merge remote-tracking branch 'cifs/for-next'

Merge remote-tracking branch 'ceph/testing'

Merge remote-tracking branch 'xtensa/for_next'

Merge remote-tracking branch 'sh/sh-latest'

Conflicts:
arch/sh/kernel/cpu/sh2a/Makefile

Merge remote-tracking branch 's390/features'

Merge remote-tracking branch 'mpc5xxx/next'

Merge remote-tracking branch 'parisc-hd/for-next'

Conflicts:
arch/parisc/include/asm/processor.h
arch/parisc/kernel/irq.c

Merge remote-tracking branch 'mips/mips-for-linux-next'

Merge remote-tracking branch 'microblaze/next'

Merge remote-tracking branch 'm68k/for-next'

Merge remote-tracking branch 'cris/for-next'

Merge remote-tracking branch 'arm64/upstream'

Merge remote-tracking branch 'xilinx/arm-next'

Conflicts:
arch/arm/mach-highbank/highbank.c
arch/arm/mach-imx/mach-imx6q.c
arch/arm/mach-spear/spear13xx.c
arch/arm/mach-vexpress/v2m.c
arch/arm/mach-zynq/platsmp.c
drivers/clocksource/Makefile
drivers/clocksource/tegra20_timer.c

Merge remote-tracking branch 'arm/for-next'

Merge remote-tracking branch 'arc/for-next'

Merge remote-tracking branch 'ide/master'

Merge remote-tracking branch 'crypto-current/master'

Merge remote-tracking branch 'wireless/master'

Merge remote-tracking branch 'sound-current/for-linus'