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| author | Toshi Kani <toshi.kani@hp.com> | 2013-08-12 09:45:53 -0600 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2013-08-13 12:20:16 +0200 |
| commit | b9d10be7a8e88fdcb12540387c219cdde87b0795 (patch) | |
| tree | ac6c78fb28efccbba5995eb55b3b151096dfff19 /include/linux/cpu.h | |
| parent | 22e7551eb6fd58352930306039a98313c011e615 (diff) | |
| download | lwn-b9d10be7a8e88fdcb12540387c219cdde87b0795.tar.gz lwn-b9d10be7a8e88fdcb12540387c219cdde87b0795.zip | |
ACPI / processor: Acquire writer lock to update CPU maps
CPU system maps are protected with reader/writer locks. The reader
lock, get_online_cpus(), assures that the maps are not updated while
holding the lock. The writer lock, cpu_hotplug_begin(), is used to
udpate the cpu maps along with cpu_maps_update_begin().
However, the ACPI processor handler updates the cpu maps without
holding the the writer lock.
acpi_map_lsapic() is called from acpi_processor_hotadd_init() to
update cpu_possible_mask and cpu_present_mask. acpi_unmap_lsapic()
is called from acpi_processor_remove() to update cpu_possible_mask.
Currently, they are either unprotected or protected with the reader
lock, which is not correct.
For example, the get_online_cpus() below is supposed to assure that
cpu_possible_mask is not changed while the code is iterating with
for_each_possible_cpu().
get_online_cpus();
for_each_possible_cpu(cpu) {
:
}
put_online_cpus();
However, this lock has no protection with CPU hotplug since the ACPI
processor handler does not use the writer lock when it updates
cpu_possible_mask. The reader lock does not serialize within the
readers.
This patch protects them with the writer lock with cpu_hotplug_begin()
along with cpu_maps_update_begin(), which must be held before calling
cpu_hotplug_begin(). It also protects arch_register_cpu() /
arch_unregister_cpu(), which creates / deletes a sysfs cpu device
interface. For this purpose it changes cpu_hotplug_begin() and
cpu_hotplug_done() to global and exports them in cpu.h.
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'include/linux/cpu.h')
| -rw-r--r-- | include/linux/cpu.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/cpu.h b/include/linux/cpu.h index ab0eade73039..956c0a16566f 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -172,6 +172,8 @@ extern struct bus_type cpu_subsys; #ifdef CONFIG_HOTPLUG_CPU /* Stop CPUs going up and down. */ +extern void cpu_hotplug_begin(void); +extern void cpu_hotplug_done(void); extern void get_online_cpus(void); extern void put_online_cpus(void); extern void cpu_hotplug_disable(void); @@ -197,6 +199,8 @@ static inline void cpu_hotplug_driver_unlock(void) #else /* CONFIG_HOTPLUG_CPU */ +static inline void cpu_hotplug_begin(void) {} +static inline void cpu_hotplug_done(void) {} #define get_online_cpus() do { } while (0) #define put_online_cpus() do { } while (0) #define cpu_hotplug_disable() do { } while (0) |