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 still need to update the documentation to remove references to cpu_up/down and advocate for device_online/offline instead if this series will make its way through. 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 6 patches fixes arch users. The next 5 patches fixes generic code users. Particularly creating a new special exported API for the device core to use instead of cpu_up/down. Maybe we can do something more restrictive than that. 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 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 <[email protected]> CC: Benjamin Herrenschmidt <[email protected]> CC: Bjorn Helgaas <[email protected]> CC: Borislav Petkov <[email protected]> CC: Boris Ostrovsky <[email protected]> CC: Catalin Marinas <[email protected]> CC: Christophe Leroy <[email protected]> CC: Daniel Lezcano <[email protected]> CC: Davidlohr Bueso <[email protected]> CC: "David S. Miller" <[email protected]> CC: Eiichi Tsukata <[email protected]> CC: Enrico Weigelt <[email protected]> CC: Fenghua Yu <[email protected]> CC: Greg Kroah-Hartman <[email protected]> CC: Helge Deller <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: Ingo Molnar <[email protected]> CC: "James E.J. Bottomley" <[email protected]> CC: James Morse <[email protected]> CC: Jiri Kosina <[email protected]> CC: Josh Poimboeuf <[email protected]> CC: Josh Triplett <[email protected]> CC: Juergen Gross <[email protected]> CC: Lorenzo Pieralisi <[email protected]> CC: Mark Rutland <[email protected]> CC: Michael Ellerman <[email protected]> CC: Nadav Amit <[email protected]> CC: Nicholas Piggin <[email protected]> CC: "Paul E. McKenney" <[email protected]> CC: Paul Mackerras <[email protected]> CC: Pavankumar Kondeti <[email protected]> CC: "Peter Zijlstra (Intel)" <[email protected]> CC: "Rafael J. Wysocki" <[email protected]> CC: Ram Pai <[email protected]> CC: Richard Fontana <[email protected]> CC: Sakari Ailus <[email protected]> CC: Stefano Stabellini <[email protected]> CC: Steve Capper <[email protected]> CC: Thiago Jung Bauermann <[email protected]> CC: Thomas Gleixner <[email protected]> CC: Tony Luck <[email protected]> CC: Will Deacon <[email protected]> CC: Zhenzhong Duan <[email protected]> CC: [email protected] CC: [email protected] CC: [email protected] CC: [email protected] CC: [email protected] CC: [email protected] CC: [email protected] CC: [email protected] Qais Yousef (12): arm64: hibernate.c: create a new function to handle cpu_up(sleep_cpu) x86: Replace cpu_up/down with devcie_online/offline powerpc: Replace cpu_up/down with device_online/offline ia64: Replace cpu_down with freeze_secondary_cpus sparc: Replace cpu_up/down with device_online/offline parisc: Replace cpu_up/down with device_online/offline driver: base: cpu: export device_online/offline driver: xen: Replace cpu_up/down with device_online/offline firmware: psci: Replace cpu_up/down with device_online/offline torture: Replace cpu_up/down with device_online/offline smp: Create a new function to bringup nonboot cpus online cpu: Hide cpu_up/down arch/arm64/kernel/hibernate.c | 13 +++---- arch/ia64/kernel/process.c | 8 +--- arch/parisc/kernel/processor.c | 4 +- arch/powerpc/kernel/machine_kexec_64.c | 4 +- arch/sparc/kernel/ds.c | 8 +++- arch/x86/kernel/topology.c | 4 +- arch/x86/mm/mmio-mod.c | 8 +++- arch/x86/xen/smp.c | 4 +- drivers/base/core.c | 4 ++ drivers/base/cpu.c | 4 +- drivers/firmware/psci/psci_checker.c | 6 ++- drivers/xen/cpu_hotplug.c | 2 +- include/linux/cpu.h | 6 ++- kernel/cpu.c | 53 ++++++++++++++++++++++++-- kernel/smp.c | 9 +---- kernel/torture.c | 15 ++++++-- 16 files changed, 106 insertions(+), 46 deletions(-) -- 2.17.1 _______________________________________________ Xen-devel mailing list [email protected] https://lists.xenproject.org/mailman/listinfo/xen-devel
