From cd8e2b48daee891011a4f21e2c62b210d24dcc9e Mon Sep 17 00:00:00 2001
From: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Date: Fri, 21 Oct 2005 19:22:00 -0400
Subject: [ACPI] fix 2.6.13 boot hang regression on HT box w/ broken BIOS

http://bugzilla.kernel.org/show_bug.cgi?id=5452

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
index 4217925..0c561c5 100644
--- a/drivers/acpi/processor_core.c
+++ b/drivers/acpi/processor_core.c
@@ -543,6 +543,8 @@ static int acpi_processor_get_info(struct acpi_processor *pr)
 	return_VALUE(0);
 }
 
+static void *processor_device_array[NR_CPUS];
+
 static int acpi_processor_start(struct acpi_device *device)
 {
 	int result = 0;
@@ -561,6 +563,19 @@ static int acpi_processor_start(struct acpi_device *device)
 
 	BUG_ON((pr->id >= NR_CPUS) || (pr->id < 0));
 
+	/*
+	 * Buggy BIOS check
+	 * ACPI id of processors can be reported wrongly by the BIOS.
+	 * Don't trust it blindly
+	 */
+	if (processor_device_array[pr->id] != NULL &&
+	    processor_device_array[pr->id] != (void *)device) {
+		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "BIOS reporting wrong ACPI id"
+			"for the processor\n"));
+		return_VALUE(-ENODEV);
+	}
+	processor_device_array[pr->id] = (void *)device;
+
 	processors[pr->id] = pr;
 
 	result = acpi_processor_add_fs(device);
-- 
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