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Subject[PATCH 2/2] ACPI: Acquire writer lock to update cpu maps
Date
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.

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.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
drivers/acpi/acpi_processor.c | 21 ++++++++++++++++-----
1 file 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));


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