forked from Minki/linux
5e5041f352
Even if acpi_processor_handle_eject() offlines cpu, there is a chance
to online the cpu after that. So the patch closes the window by using
get/put_online_cpus().
Why does the patch change _cpu_up() logic?
The patch cares the race of hot-remove cpu and _cpu_up(). If the patch
does not change it, there is the following race.
hot-remove cpu | _cpu_up()
------------------------------------- ------------------------------------
call acpi_processor_handle_eject() |
call cpu_down() |
call get_online_cpus() |
| call cpu_hotplug_begin() and stop here
call arch_unregister_cpu() |
call acpi_unmap_lsapic() |
call put_online_cpus() |
| start and continue _cpu_up()
return acpi_processor_remove() |
continue hot-remove the cpu |
So _cpu_up() can continue to itself. And hot-remove cpu can also continue
itself. If the patch changes _cpu_up() logic, the race disappears as below:
hot-remove cpu | _cpu_up()
-----------------------------------------------------------------------
call acpi_processor_handle_eject() |
call cpu_down() |
call get_online_cpus() |
| call cpu_hotplug_begin() and stop here
call arch_unregister_cpu() |
call acpi_unmap_lsapic() |
cpu's cpu_present is set |
to false by set_cpu_present()|
call put_online_cpus() |
| start _cpu_up()
| check cpu_present() and return -EINVAL
return acpi_processor_remove() |
continue hot-remove the cpu |
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Reviewed-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
|
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|---|---|---|
| .. | ||
| acpica | ||
| apei | ||
| ac.c | ||
| acpi_ipmi.c | ||
| acpi_memhotplug.c | ||
| acpi_pad.c | ||
| battery.c | ||
| bgrt.c | ||
| blacklist.c | ||
| bus.c | ||
| button.c | ||
| cm_sbs.c | ||
| container.c | ||
| custom_method.c | ||
| debugfs.c | ||
| dock.c | ||
| ec_sys.c | ||
| ec.c | ||
| event.c | ||
| fan.c | ||
| glue.c | ||
| hed.c | ||
| internal.h | ||
| Kconfig | ||
| Makefile | ||
| numa.c | ||
| nvs.c | ||
| osl.c | ||
| pci_bind.c | ||
| pci_irq.c | ||
| pci_link.c | ||
| pci_root.c | ||
| pci_slot.c | ||
| power.c | ||
| proc.c | ||
| processor_core.c | ||
| processor_driver.c | ||
| processor_idle.c | ||
| processor_perflib.c | ||
| processor_thermal.c | ||
| processor_throttling.c | ||
| reboot.c | ||
| sbs.c | ||
| sbshc.c | ||
| sbshc.h | ||
| scan.c | ||
| sleep.c | ||
| sleep.h | ||
| sysfs.c | ||
| tables.c | ||
| thermal.c | ||
| utils.c | ||
| video_detect.c | ||
| video.c | ||
| wakeup.c | ||