diff options
author | Toshi Kani <toshi.kani@hp.com> | 2013-08-12 15:45:53 (GMT) |
---|---|---|
committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2013-08-13 10:20:16 (GMT) |
commit | b9d10be7a8e88fdcb12540387c219cdde87b0795 (patch) | |
tree | ac6c78fb28efccbba5995eb55b3b151096dfff19 /drivers/acpi/acpi_processor.c | |
parent | 22e7551eb6fd58352930306039a98313c011e615 (diff) | |
download | linux-fsl-qoriq-b9d10be7a8e88fdcb12540387c219cdde87b0795.tar.xz |
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 'drivers/acpi/acpi_processor.c')
-rw-r--r-- | drivers/acpi/acpi_processor.c | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c index 5a74a9c..f29e06e 100644 --- a/drivers/acpi/acpi_processor.c +++ b/drivers/acpi/acpi_processor.c @@ -178,14 +178,17 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr) if (ACPI_FAILURE(status) || !(sta & ACPI_STA_DEVICE_PRESENT)) return -ENODEV; + cpu_maps_update_begin(); + cpu_hotplug_begin(); + ret = acpi_map_lsapic(pr->handle, &pr->id); if (ret) - return ret; + goto out; ret = arch_register_cpu(pr->id); if (ret) { acpi_unmap_lsapic(pr->id); - return ret; + goto out; } /* @@ -195,7 +198,11 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr) */ pr_info("CPU%d has been hot-added\n", pr->id); pr->flags.need_hotplug_init = 1; - return 0; + +out: + cpu_hotplug_done(); + cpu_maps_update_done(); + return ret; } #else static inline int acpi_processor_hotadd_init(struct acpi_processor *pr) @@ -452,11 +459,15 @@ static void acpi_processor_remove(struct acpi_device *device) per_cpu(processor_device_array, pr->id) = NULL; per_cpu(processors, pr->id) = NULL; + cpu_maps_update_begin(); + cpu_hotplug_begin(); + /* Remove the CPU. */ - get_online_cpus(); arch_unregister_cpu(pr->id); acpi_unmap_lsapic(pr->id); - put_online_cpus(); + + cpu_hotplug_done(); + cpu_maps_update_done(); try_offline_node(cpu_to_node(pr->id)); |