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authorToshi Kani <toshi.kani@hp.com>2013-08-12 09:45:53 -0600
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-08-13 12:20:16 +0200
commitb9d10be7a8e88fdcb12540387c219cdde87b0795 (patch)
treeac6c78fb28efccbba5995eb55b3b151096dfff19 /include/linux/cpu.h
parent22e7551eb6fd58352930306039a98313c011e615 (diff)
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.h4
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)