[PATCH v3 00/15] Convert cpu_up/down to device_online/offline

[Qais Yousef]

Changes in v3:
	* Fixup smp_shutdown_nonboot_cpus() to hold the right lock as suggested
	  by Russel King.
	* Split the combined arm/arm64 patch into 2 separate patches.
	* Add new add/remove_cpu() functions that wraps lock,
	  device_online/offline, unlock as suggested by Paul McKenney
	* Use the new add/remove instead of device_online/offline where
	  appropriate
	* Dropped a patch that exported device_online/offline() since
	  the new add/remove_cpu() are exported and used by torture test which
	  could build as a module
	* Rebsed on top 5.6-rc1 from linus/master


	git clone git://linux-arm.org/linux-qy.git -b cpu-hp-cleanup-v3


Older post can be found here:
	https://lore.kernel.org/linuxppc-dev/20191125112754.25223-1-qais.yousef@arm.com/
	https://lore.kernel.org/lkml/20191125112754.25223-2-qais.yousef@arm.com/


Using cpu_up/down directly to bring cpus online/offline loses synchronization
with sysfs and could suffer from a race similar to what is described in
commit a6717c01ddc2 ("powerpc/rtas: use device model APIs and serialization
during LPM").

cpu_up/down seem to be more of a internal implementation detail for the cpu
subsystem to use to boot up cpus, perform suspend/resume and low level hotplug
operations. Users outside of the cpu subsystem would be better using the device
core API to bring a cpu online/offline which is the interface used to hotplug
memory and other system devices.

Several users have already migrated to use the device core API, this series
converts the remaining users and hides cpu_up/down from internal users at the
end.

I noticed this problem while working on a hack to disable offlining
a particular CPU but noticed that setting the offline_disabled attribute in the
device struct isn't enough because users can easily bypass the device core.
While my hack isn't a valid use case but it did highlight the inconsistency in
the way cpus are being onlined/offlined and this attempt hopefully improves on
this.

The first 9 patches fix arch users.

The remaining 6 patches fix generic code users. Particularly creating a new
special exported API for the device core to use instead of cpu_up/down.

The last patch removes cpu_up/down from cpu.h and unexport the functions.

In some cases where the use of cpu_up/down seemed legitimate, I encapsulated
the logic in a higher level - special purposed function; and converted the code
to use that instead.

I did re-run the rcu torture, lock torture and psci checker tests and no
problem was noticed. I did perform build tests on all arch affected except for
parisc.

Hopefully I got the CC list right for all the patches. Apologies in advance if
some people were omitted from some patches but they should have been CCed.

CC: Armijn Hemel <armijn at tjaldur.nl>
CC: Benjamin Herrenschmidt <benh at kernel.crashing.org>
CC: Bjorn Helgaas <bhelgaas at google.com>
CC: Borislav Petkov <bp at alien8.de>
CC: Boris Ostrovsky <boris.ostrovsky at oracle.com>
CC: Catalin Marinas <catalin.marinas at arm.com>
CC: Christophe Leroy <christophe.leroy at c-s.fr>
CC: Daniel Lezcano <daniel.lezcano at linaro.org>
CC: Davidlohr Bueso <dave at stgolabs.net>
CC: "David S. Miller" <davem at davemloft.net>
CC: Eiichi Tsukata <devel at etsukata.com>
CC: Enrico Weigelt <info at metux.net>
CC: Fenghua Yu <fenghua.yu at intel.com>
CC: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
CC: Helge Deller <deller at gmx.de>
CC: "H. Peter Anvin" <hpa at zytor.com>
CC: Ingo Molnar <mingo at kernel.org>
CC: "James E.J. Bottomley" <James.Bottomley at HansenPartnership.com>
CC: James Morse <james.morse at arm.com>
CC: Jiri Kosina <jkosina at suse.cz>
CC: Josh Poimboeuf <jpoimboe at redhat.com>
CC: Josh Triplett <josh at joshtriplett.org>
CC: Juergen Gross <jgross at suse.com>
CC: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
CC: Mark Rutland <mark.rutland at arm.com>
CC: Michael Ellerman <mpe at ellerman.id.au>
CC: Nadav Amit <namit at vmware.com>
CC: Nicholas Piggin <npiggin at gmail.com>
CC: "Paul E. McKenney" <paulmck at kernel.org>
CC: Paul Mackerras <paulus at samba.org>
CC: Pavankumar Kondeti <pkondeti at codeaurora.org>
CC: "Peter Zijlstra (Intel)" <peterz at infradead.org>
CC: "Rafael J. Wysocki" <rafael at kernel.org>
CC: Ram Pai <linuxram at us.ibm.com>
CC: Richard Fontana <rfontana at redhat.com>
CC: Russell King <linux at armlinux.org.uk>
CC: Sakari Ailus <sakari.ailus at linux.intel.com>
CC: Stefano Stabellini <sstabellini at kernel.org>
CC: Steve Capper <steve.capper at arm.com>
CC: Thiago Jung Bauermann <bauerman at linux.ibm.com>
CC: Thomas Gleixner <tglx at linutronix.de>
CC: Tony Luck <tony.luck at intel.com>
CC: Will Deacon <will at kernel.org>
CC: Zhenzhong Duan <zhenzhong.duan at oracle.com>
CC: linux-arm-kernel at lists.infradead.org
CC: linux-ia64 at vger.kernel.org
CC: linux-kernel at vger.kernel.org
CC: linux-parisc at vger.kernel.org
CC: linuxppc-dev at lists.ozlabs.org
CC: sparclinux at vger.kernel.org
CC: x86 at kernel.org
CC: xen-devel at lists.xenproject.org


Qais Yousef (15):
  cpu: Add new {add,remove}_cpu() functions
  smp: Create a new function to shutdown nonboot cpus
  ia64: Replace cpu_down with smp_shutdown_nonboot_cpus()
  arm: Don't use disable_nonboot_cpus()
  arm64: Don't use disable_nonboot_cpus()
  arm64: hibernate.c: Create a new function to handle cpu_up(sleep_cpu)
  x86: Replace cpu_up/down with add/remove_cpu
  powerpc: Replace cpu_up/down with add/remove_cpu
  sparc: Replace cpu_up/down with add/remove_cpu
  parisc: Replace cpu_up/down with add/remove_cpu
  driver: xen: Replace cpu_up/down with device_online/offline
  firmware: psci: Replace cpu_up/down with add/remove_cpu
  torture: Replace cpu_up/down with add/remove_cpu
  smp: Create a new function to bringup nonboot cpus online
  cpu: Hide cpu_up/down

 arch/arm/kernel/reboot.c             |   4 +-
 arch/arm64/kernel/hibernate.c        |  13 +--
 arch/arm64/kernel/process.c          |   4 +-
 arch/ia64/kernel/process.c           |   8 +-
 arch/parisc/kernel/processor.c       |   2 +-
 arch/powerpc/kexec/core_64.c         |   2 +-
 arch/sparc/kernel/ds.c               |   4 +-
 arch/x86/kernel/topology.c           |  22 ++---
 arch/x86/mm/mmio-mod.c               |   4 +-
 arch/x86/xen/smp.c                   |   2 +-
 drivers/base/cpu.c                   |   4 +-
 drivers/firmware/psci/psci_checker.c |   4 +-
 drivers/xen/cpu_hotplug.c            |   2 +-
 include/linux/cpu.h                  |  10 +-
 kernel/cpu.c                         | 134 ++++++++++++++++++++++++++-
 kernel/smp.c                         |   9 +-
 kernel/torture.c                     |   9 +-
 17 files changed, 172 insertions(+), 65 deletions(-)

-- 
2.17.1