[ACPIHP PATCH part4 8/9] ACPI/processor: serialize call to acpi_map/unmap_lsapic

[Jiang Liu <liuj97@gmail.com>]

Function acpi_map_lsapic() is used to allocate CPU id for hot-added
CPUs and acpi_unmap_lsapic() is used to free CPU id for hot-removed
CPUs. But currently there's no mechanism to serialze the CPU id
allocation/free process, which may cause wrong CPU id assignment
when handling concurrent CPU online/offline operations. So introuce
a mutex to serialize CPU id allocation/free.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
---
 drivers/acpi/processor_driver.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index 9a02210..6dbce2f 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -108,6 +108,7 @@ static struct acpi_driver acpi_processor_driver = {
 	.drv.pm = &acpi_processor_pm,
 };
 
+static DEFINE_MUTEX(acpi_processor_mutex);
 static DEFINE_PER_CPU(void *, processor_device_array);
 
 DEFINE_PER_CPU(struct acpi_processor *, processors);
@@ -668,7 +669,9 @@ static void acpi_processor_reset(struct acpi_device *device, struct acpi_process
 	acpi_processor_unlink(device, pr);
 	put_online_cpus();
 	arch_unregister_cpu(pr->id);
+	mutex_lock(&acpi_processor_mutex);
 	acpi_unmap_lsapic(pr->id);
+	mutex_unlock(&acpi_processor_mutex);
 	pr->id = -1;
 }
 
@@ -703,14 +706,18 @@ static int acpi_processor_pre_configure(struct acpi_device *device,
 		if (pr->apic_id == -1)
 			return result;
 
+		mutex_lock(&acpi_processor_mutex);
 		result = acpi_map_lsapic(device->handle, pr->apic_id, &pr->id);
+		mutex_unlock(&acpi_processor_mutex);
 		if (result)
 			return result;
 		BUG_ON((pr->id >= nr_cpu_ids) || (pr->id < 0));
 
 		result = arch_register_cpu(pr->id, 1);
 		if (result) {
+			mutex_lock(&acpi_processor_mutex);
 			acpi_unmap_lsapic(pr->id);
+			mutex_unlock(&acpi_processor_mutex);
 			pr->id = -1;
 			return result;
 		}
-- 
1.7.9.5

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