x86: fix stack overflow for large values of MAX_APICS

physid_mask_of_physid() causes a huge stack (12k) to be created if the
number of APICS is large. Replace physid_mask_of_physid() with a
new function that does not create large stacks. This is a problem only
on large x86_64 systems.

this paves the way to increase MAX_APICS.
Signed-off-by: NJack Steiner <steiner@sgi.com>
Cc: linux-mm@kvack.org
Cc: mingo@elte.hu
Cc: tglx@linutronix.de
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/apic_32.c

@@ -1269,7 +1269,7 @@ int __init APIC_init_uniprocessor(void)
 #ifdef CONFIG_CRASH_DUMP
 	boot_cpu_physical_apicid = GET_APIC_ID(read_apic_id());
 #endif
-	phys_cpu_present_map = physid_mask_of_physid(boot_cpu_physical_apicid);
+	physid_set_mask_of_physid(boot_cpu_physical_apicid, &phys_cpu_present_map);
 
 	setup_local_APIC();
 

arch/x86/kernel/apic_64.c

@@ -942,7 +942,7 @@ int __init APIC_init_uniprocessor(void)
 
 	verify_local_APIC();
 
-	phys_cpu_present_map = physid_mask_of_physid(boot_cpu_physical_apicid);
+	physid_set_mask_of_physid(boot_cpu_physical_apicid, &phys_cpu_present_map);
 	apic_write(APIC_ID, SET_APIC_ID(boot_cpu_physical_apicid));
 
 	setup_local_APIC();

arch/x86/kernel/smpboot.c

@@ -1091,10 +1091,9 @@ static __init void disable_smp(void)
 	smpboot_clear_io_apic_irqs();
 #endif
 	if (smp_found_config)
-		phys_cpu_present_map =
-				physid_mask_of_physid(boot_cpu_physical_apicid);
+		physid_set_mask_of_physid(boot_cpu_physical_apicid, &phys_cpu_present_map);
 	else
-		phys_cpu_present_map = physid_mask_of_physid(0);
+		physid_set_mask_of_physid(0, &phys_cpu_present_map);
 	map_cpu_to_logical_apicid();
 	cpu_set(0, per_cpu(cpu_sibling_map, 0));
 	cpu_set(0, per_cpu(cpu_core_map, 0));

include/asm-x86/mpspec.h

@@ -101,6 +101,7 @@ typedef struct physid_mask physid_mask_t;
 		__physid_mask;						\
 	})
 
+/* Note: will create very large stack frames if physid_mask_t is big */
 #define physid_mask_of_physid(physid)					\
 	({								\
 		physid_mask_t __physid_mask = PHYSID_MASK_NONE;		\
@@ -108,6 +109,12 @@ typedef struct physid_mask physid_mask_t;
 		__physid_mask;						\
 	})
 
+static inline void physid_set_mask_of_physid(int physid, physid_mask_t *map)
+{
+	physids_clear(*map);
+	physid_set(physid, *map);
+}
+
 #define PHYSID_MASK_ALL		{ {[0 ... PHYSID_ARRAY_SIZE-1] = ~0UL} }
 #define PHYSID_MASK_NONE	{ {[0 ... PHYSID_ARRAY_SIZE-1] = 0UL} }