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Groups > linux.kernel > #1624102
| From | Thomas Gleixner <tglx@linutronix.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [patch 00/20] cpu/hotplug: Convert get_online_cpus() to a percpu_rwsem |
| Date | 2017-04-15 19:40 +0200 |
| Message-ID | <twzPX-123-3@gated-at.bofh.it> (permalink) |
| Organization | linux.* mail to news gateway |
get_online_cpus() is used in hot pathes in mainline and even more so in
RT. That can show up badly under certain conditions because every locker
contends on a global mutex. RT has it's own homebrewn mitigation which is
an (badly done) open coded implementation of percpu_rwsems with recursion
support.
The proper replacement for that are percpu_rwsems, but that requires to
remove recursion support.
The conversion unearthed real locking issues which were previously not
visible because the get_online_cpus() lockdep annotation was implemented
with recursion support which prevents lockdep from tracking full dependency
chains. These potential deadlocks are not related to recursive calls, they
trigger on the first invocation because lockdep now has the full dependency
chains available.
The following patch series addresses this by
- Cleaning up places which call get_online_cpus() nested
- Replacing a few instances with cpu_hotplug_disable() to prevent circular
locking dependencies.
The series depends on
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core
plus
Linus tree merged in to avoid conflicts
It's available in git from
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git WIP.hotplug
Thanks,
tglx
-------
arch/arm/kernel/hw_breakpoint.c | 5
arch/powerpc/kvm/book3s_hv.c | 8 -
arch/powerpc/platforms/powernv/subcore.c | 2
arch/s390/kernel/time.c | 2
arch/x86/events/core.c | 1
arch/x86/events/intel/core.c | 4
arch/x86/events/intel/cqm.c | 12 +-
arch/x86/kernel/cpu/mtrr/main.c | 2
drivers/acpi/processor_driver.c | 4
drivers/cpufreq/cpufreq.c | 9 -
drivers/hwtracing/coresight/coresight-etm3x.c | 12 +-
drivers/hwtracing/coresight/coresight-etm4x.c | 12 +-
drivers/pci/pci-driver.c | 46 ++++----
include/linux/cpuhotplug.h | 29 +++++
include/linux/padata.h | 3
include/linux/pci.h | 1
include/linux/stop_machine.h | 26 ++++
kernel/cpu.c | 149 +++++++-------------------
kernel/padata.c | 38 +++---
kernel/stop_machine.c | 4
20 files changed, 177 insertions(+), 192 deletions(-)
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[patch 00/20] cpu/hotplug: Convert get_online_cpus() to a percpu_rwsem Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 02/20] stop_machine: Provide stop_machine_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 20/20] cpu/hotplug: Convert hotplug locking to percpu rwsem Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
Re: [patch 20/20] cpu/hotplug: Convert hotplug locking to percpu rwsem Peter Zijlstra <peterz@infradead.org> - 2017-04-17 09:00 +0200
[patch 17/20] PCI: Use cpu_hotplug_disable() instead of get_online_cpus() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
Re: [patch 17/20] PCI: Use cpu_hotplug_disable() instead of get_online_cpus() Peter Zijlstra <peterz@infradead.org> - 2017-04-17 08:50 +0200
Re: [patch 17/20] PCI: Use cpu_hotplug_disable() instead of get_online_cpus() Thomas Gleixner <tglx@linutronix.de> - 2017-04-17 09:50 +0200
Re: [patch 17/20] PCI: Use cpu_hotplug_disable() instead of get_online_cpus() Bjorn Helgaas <helgaas@kernel.org> - 2017-04-18 21:50 +0200
Re: [patch 17/20] PCI: Use cpu_hotplug_disable() instead of get_online_cpus() Thomas Gleixner <tglx@linutronix.de> - 2017-04-18 22:00 +0200
[patch 12/20] s390/kernel: Use stop_machine_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 13/20] powerpc/powernv: Use stop_machine_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 03/20] padata: Make padata_alloc() static Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
Re: [patch 03/20] padata: Make padata_alloc() static "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-16 08:30 +0200
Re: [patch 03/20] padata: Make padata_alloc() static Thomas Gleixner <tglx@linutronix.de> - 2017-04-17 11:20 +0200
[patch 01/20] cpu/hotplug: Provide cpuhp_setup/remove_state[_nocalls]_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 18/20] PCI: Replace the racy recursion prevention Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 04/20] padata: Avoid nested calls to get_online_cpus() in pcrypt_init_padata() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 14/20] kernel/hotplug: Use stop_machine_locked() in takedown_cpu() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 05/20] x86/mtrr: Remove get_online_cpus() from mtrr_save_state() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 07/20] KVM/PPC/Book3S HV: Use cpuhp_setup_state_nocalls_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 16/20] perf/x86/intel: Drop get_online_cpus() in intel_snb_check_microcode() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
Re: [patch 16/20] perf/x86/intel: Drop get_online_cpus() in intel_snb_check_microcode() Borislav Petkov <bp@alien8.de> - 2017-04-18 13:30 +0200
[patch 09/20] hwtracing/coresight-etm4x: Use cpuhp_setup_state_nocalls_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 10/20] perf/x86/intel/cqm: Use cpuhp_setup_state_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 06/20] cpufreq: Use cpuhp_setup_state_nocalls_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
Re: [patch 06/20] cpufreq: Use cpuhp_setup_state_nocalls_locked() "Rafael J. Wysocki" <rafael@kernel.org> - 2017-04-16 01:00 +0200
Re: [patch 06/20] cpufreq: Use cpuhp_setup_state_nocalls_locked() Viresh Kumar <viresh.kumar@linaro.org> - 2017-04-17 06:20 +0200
[patch 08/20] hwtracing/coresight-etm3x: Use the locked version of cpuhp_setup_state_nocalls() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
[patch 11/20] ARM/hw_breakpoint: Use cpuhp_setup_state_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
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