cpumask: centralize cpu_online_map and cpu_possible_map

Impact: cleanup

Each SMP arch defines these themselves.  Move them to a central
location.

Twists:
1) Some archs (m32, parisc, s390) set possible_map to all 1, so we add a
   CONFIG_INIT_ALL_POSSIBLE for this rather than break them.

2) mips and sparc32 '#define cpu_possible_map phys_cpu_present_map'.
   Those archs simply have phys_cpu_present_map replaced everywhere.

3) Alpha defined cpu_possible_map to cpu_present_map; this is tricky
   so I just manipulate them both in sync.

4) IA64, cris and m32r have gratuitous 'extern cpumask_t cpu_possible_map'
   declarations.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Reviewed-by: NGrant Grundler <grundler@parisc-linux.org>
Tested-by: NTony Luck <tony.luck@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Mike Travis <travis@sgi.com>
Cc: ink@jurassic.park.msu.ru
Cc: rmk@arm.linux.org.uk
Cc: starvik@axis.com
Cc: tony.luck@intel.com
Cc: takata@linux-m32r.org
Cc: ralf@linux-mips.org
Cc: grundler@parisc-linux.org
Cc: paulus@samba.org
Cc: schwidefsky@de.ibm.com
Cc: lethal@linux-sh.org
Cc: wli@holomorphy.com
Cc: davem@davemloft.net
Cc: jdike@addtoit.com
Cc: mingo@redhat.com

arch/alpha/include/asm/smp.h

@@ -45,7 +45,6 @@ extern struct cpuinfo_alpha cpu_data[NR_CPUS];
 #define raw_smp_processor_id()	(current_thread_info()->cpu)
 
 extern int smp_num_cpus;
-#define cpu_possible_map	cpu_present_map
 
 extern void arch_send_call_function_single_ipi(int cpu);
 extern void arch_send_call_function_ipi(cpumask_t mask);

arch/alpha/kernel/process.c

@@ -94,6 +94,7 @@ common_shutdown_1(void *generic_ptr)
 		flags |= 0x00040000UL; /* "remain halted" */
 		*pflags = flags;
 		cpu_clear(cpuid, cpu_present_map);
+		cpu_clear(cpuid, cpu_possible_map);
 		halt();
 	}
 #endif
@@ -120,6 +121,7 @@ common_shutdown_1(void *generic_ptr)
 #ifdef CONFIG_SMP
 	/* Wait for the secondaries to halt. */
 	cpu_clear(boot_cpuid, cpu_present_map);
+	cpu_clear(boot_cpuid, cpu_possible_map);
 	while (cpus_weight(cpu_present_map))
 		barrier();
 #endif

arch/alpha/kernel/smp.c

@@ -70,11 +70,6 @@ enum ipi_message_type {
 /* Set to a secondary's cpuid when it comes online.  */
 static int smp_secondary_alive __devinitdata = 0;
 
-/* Which cpus ids came online.  */
-cpumask_t cpu_online_map;
-
-EXPORT_SYMBOL(cpu_online_map);
-
 int smp_num_probed;		/* Internal processor count */
 int smp_num_cpus = 1;		/* Number that came online.  */
 EXPORT_SYMBOL(smp_num_cpus);
@@ -440,6 +435,7 @@ setup_smp(void)
 				((char *)cpubase + i*hwrpb->processor_size);
 			if ((cpu->flags & 0x1cc) == 0x1cc) {
 				smp_num_probed++;
+				cpu_set(i, cpu_possible_map);
 				cpu_set(i, cpu_present_map);
 				cpu->pal_revision = boot_cpu_palrev;
 			}
@@ -473,6 +469,7 @@ smp_prepare_cpus(unsigned int max_cpus)
 
 	/* Nothing to do on a UP box, or when told not to.  */
 	if (smp_num_probed == 1 || max_cpus == 0) {
+		cpu_possible_map = cpumask_of_cpu(boot_cpuid);
 		cpu_present_map = cpumask_of_cpu(boot_cpuid);
 		printk(KERN_INFO "SMP mode deactivated.\n");
 		return;

arch/arm/kernel/smp.c

@@ -33,16 +33,6 @@
 #include <asm/tlbflush.h>
 #include <asm/ptrace.h>
 
-/*
- * bitmask of present and online CPUs.
- * The present bitmask indicates that the CPU is physically present.
- * The online bitmask indicates that the CPU is up and running.
- */
-cpumask_t cpu_possible_map;
-EXPORT_SYMBOL(cpu_possible_map);
-cpumask_t cpu_online_map;
-EXPORT_SYMBOL(cpu_online_map);
-
 /*
  * as from 2.5, kernels no longer have an init_tasks structure
  * so we need some other way of telling a new secondary core

arch/cris/arch-v32/kernel/smp.c

@@ -29,11 +29,7 @@
 spinlock_t cris_atomic_locks[] = { [0 ... LOCK_COUNT - 1] = SPIN_LOCK_UNLOCKED};
 
 /* CPU masks */
-cpumask_t cpu_online_map = CPU_MASK_NONE;
-EXPORT_SYMBOL(cpu_online_map);
 cpumask_t phys_cpu_present_map = CPU_MASK_NONE;
-cpumask_t cpu_possible_map;
-EXPORT_SYMBOL(cpu_possible_map);
 EXPORT_SYMBOL(phys_cpu_present_map);
 
 /* Variables used during SMP boot */

arch/cris/include/asm/smp.h

@@ -4,7 +4,6 @@
 #include <linux/cpumask.h>
 
 extern cpumask_t phys_cpu_present_map;
-extern cpumask_t cpu_possible_map;
 
 #define raw_smp_processor_id() (current_thread_info()->cpu)
 

arch/ia64/include/asm/smp.h

@@ -57,7 +57,6 @@ extern struct smp_boot_data {
 
 extern char no_int_routing __devinitdata;
 
-extern cpumask_t cpu_online_map;
 extern cpumask_t cpu_core_map[NR_CPUS];
 DECLARE_PER_CPU(cpumask_t, cpu_sibling_map);
 extern int smp_num_siblings;

arch/ia64/kernel/smpboot.c

@@ -131,12 +131,6 @@ struct task_struct *task_for_booting_cpu;
  */
 DEFINE_PER_CPU(int, cpu_state);
 
-/* Bitmasks of currently online, and possible CPUs */
-cpumask_t cpu_online_map;
-EXPORT_SYMBOL(cpu_online_map);
-cpumask_t cpu_possible_map = CPU_MASK_NONE;
-EXPORT_SYMBOL(cpu_possible_map);
-
 cpumask_t cpu_core_map[NR_CPUS] __cacheline_aligned;
 EXPORT_SYMBOL(cpu_core_map);
 DEFINE_PER_CPU_SHARED_ALIGNED(cpumask_t, cpu_sibling_map);

arch/m32r/Kconfig

@@ -10,6 +10,7 @@ config M32R
 	default y
 	select HAVE_IDE
 	select HAVE_OPROFILE
+	select INIT_ALL_POSSIBLE
 
 config SBUS
 	bool

arch/m32r/kernel/smpboot.c

@@ -73,17 +73,11 @@ static unsigned int bsp_phys_id = -1;
 /* Bitmask of physically existing CPUs */
 physid_mask_t phys_cpu_present_map;
 
-/* Bitmask of currently online CPUs */
-cpumask_t cpu_online_map;
-EXPORT_SYMBOL(cpu_online_map);
-
 cpumask_t cpu_bootout_map;
 cpumask_t cpu_bootin_map;
 static cpumask_t cpu_callin_map;
 cpumask_t cpu_callout_map;
 EXPORT_SYMBOL(cpu_callout_map);
-cpumask_t cpu_possible_map = CPU_MASK_ALL;
-EXPORT_SYMBOL(cpu_possible_map);
 
 /* Per CPU bogomips and other parameters */
 struct cpuinfo_m32r cpu_data[NR_CPUS] __cacheline_aligned;

arch/mips/include/asm/smp.h

@@ -38,9 +38,6 @@ extern int __cpu_logical_map[NR_CPUS];
 #define SMP_RESCHEDULE_YOURSELF	0x1	/* XXX braindead */
 #define SMP_CALL_FUNCTION	0x2
 
-extern cpumask_t phys_cpu_present_map;
-#define cpu_possible_map	phys_cpu_present_map
-
 extern void asmlinkage smp_bootstrap(void);
 
 /*

arch/mips/kernel/smp-cmp.c

@@ -226,7 +226,7 @@ void __init cmp_smp_setup(void)
 
 	for (i = 1; i < NR_CPUS; i++) {
 		if (amon_cpu_avail(i)) {
-			cpu_set(i, phys_cpu_present_map);
+			cpu_set(i, cpu_possible_map);
 			__cpu_number_map[i]	= ++ncpu;
 			__cpu_logical_map[ncpu]	= i;
 		}

arch/mips/kernel/smp-mt.c

@@ -70,7 +70,7 @@ static unsigned int __init smvp_vpe_init(unsigned int tc, unsigned int mvpconf0,
 		write_vpe_c0_vpeconf0(tmp);
 
 		/* Record this as available CPU */
-		cpu_set(tc, phys_cpu_present_map);
+		cpu_set(tc, cpu_possible_map);
 		__cpu_number_map[tc]	= ++ncpu;
 		__cpu_logical_map[ncpu]	= tc;
 	}

arch/mips/kernel/smp.c

@@ -44,15 +44,10 @@
 #include <asm/mipsmtregs.h>
 #endif /* CONFIG_MIPS_MT_SMTC */
 
-cpumask_t phys_cpu_present_map;		/* Bitmask of available CPUs */
 volatile cpumask_t cpu_callin_map;	/* Bitmask of started secondaries */
-cpumask_t cpu_online_map;		/* Bitmask of currently online CPUs */
 int __cpu_number_map[NR_CPUS];		/* Map physical to logical */
 int __cpu_logical_map[NR_CPUS];		/* Map logical to physical */
 
-EXPORT_SYMBOL(phys_cpu_present_map);
-EXPORT_SYMBOL(cpu_online_map);
-
 extern void cpu_idle(void);
 
 /* Number of TCs (or siblings in Intel speak) per CPU core */
@@ -195,7 +190,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 /* preload SMP state for boot cpu */
 void __devinit smp_prepare_boot_cpu(void)
 {
-	cpu_set(0, phys_cpu_present_map);
+	cpu_set(0, cpu_possible_map);
 	cpu_set(0, cpu_online_map);
 	cpu_set(0, cpu_callin_map);
 }

arch/mips/kernel/smtc.c

@@ -290,7 +290,7 @@ static void smtc_configure_tlb(void)
  * possibly leave some TCs/VPEs as "slave" processors.
  *
  * Use c0_MVPConf0 to find out how many TCs are available, setting up
- * phys_cpu_present_map and the logical/physical mappings.
+ * cpu_possible_map and the logical/physical mappings.
  */
 
 int __init smtc_build_cpu_map(int start_cpu_slot)
@@ -304,7 +304,7 @@ int __init smtc_build_cpu_map(int start_cpu_slot)
 	 */
 	ntcs = ((read_c0_mvpconf0() & MVPCONF0_PTC) >> MVPCONF0_PTC_SHIFT) + 1;
 	for (i=start_cpu_slot; i<NR_CPUS && i<ntcs; i++) {
-		cpu_set(i, phys_cpu_present_map);
+		cpu_set(i, cpu_possible_map);
 		__cpu_number_map[i] = i;
 		__cpu_logical_map[i] = i;
 	}
@@ -521,7 +521,7 @@ void smtc_prepare_cpus(int cpus)
 	 * Pull any physically present but unused TCs out of circulation.
 	 */
 	while (tc < (((val & MVPCONF0_PTC) >> MVPCONF0_PTC_SHIFT) + 1)) {
-		cpu_clear(tc, phys_cpu_present_map);
+		cpu_clear(tc, cpu_possible_map);
 		cpu_clear(tc, cpu_present_map);
 		tc++;
 	}

arch/mips/pmc-sierra/yosemite/smp.c

@@ -141,7 +141,7 @@ static void __cpuinit yos_boot_secondary(int cpu, struct task_struct *idle)
 }
 
 /*
- * Detect available CPUs, populate phys_cpu_present_map before smp_init
+ * Detect available CPUs, populate cpu_possible_map before smp_init
  *
  * We don't want to start the secondary CPU yet nor do we have a nice probing
  * feature in PMON so we just assume presence of the secondary core.
@@ -150,10 +150,10 @@ static void __init yos_smp_setup(void)
 {
 	int i;
 
-	cpus_clear(phys_cpu_present_map);
+	cpus_clear(cpu_possible_map);
 
 	for (i = 0; i < 2; i++) {
-		cpu_set(i, phys_cpu_present_map);
+		cpu_set(i, cpu_possible_map);
 		__cpu_number_map[i]	= i;
 		__cpu_logical_map[i]	= i;
 	}

arch/mips/sgi-ip27/ip27-smp.c

@@ -76,7 +76,7 @@ static int do_cpumask(cnodeid_t cnode, nasid_t nasid, int highest)
 			/* Only let it join in if it's marked enabled */
 			if ((acpu->cpu_info.flags & KLINFO_ENABLE) &&
 			    (tot_cpus_found != NR_CPUS)) {
-				cpu_set(cpuid, phys_cpu_present_map);
+				cpu_set(cpuid, cpu_possible_map);
 				alloc_cpupda(cpuid, tot_cpus_found);
 				cpus_found++;
 				tot_cpus_found++;

arch/mips/sibyte/bcm1480/smp.c

@@ -136,7 +136,7 @@ static void __cpuinit bcm1480_boot_secondary(int cpu, struct task_struct *idle)
 
 /*
  * Use CFE to find out how many CPUs are available, setting up
- * phys_cpu_present_map and the logical/physical mappings.
+ * cpu_possible_map and the logical/physical mappings.
  * XXXKW will the boot CPU ever not be physical 0?
  *
  * Common setup before any secondaries are started
@@ -145,14 +145,14 @@ static void __init bcm1480_smp_setup(void)
 {
 	int i, num;
 
-	cpus_clear(phys_cpu_present_map);
-	cpu_set(0, phys_cpu_present_map);
+	cpus_clear(cpu_possible_map);
+	cpu_set(0, cpu_possible_map);
 	__cpu_number_map[0] = 0;
 	__cpu_logical_map[0] = 0;
 
 	for (i = 1, num = 0; i < NR_CPUS; i++) {
 		if (cfe_cpu_stop(i) == 0) {
-			cpu_set(i, phys_cpu_present_map);
+			cpu_set(i, cpu_possible_map);
 			__cpu_number_map[i] = ++num;
 			__cpu_logical_map[num] = i;
 		}

arch/mips/sibyte/sb1250/smp.c

@@ -124,7 +124,7 @@ static void __cpuinit sb1250_boot_secondary(int cpu, struct task_struct *idle)
 
 /*
  * Use CFE to find out how many CPUs are available, setting up
- * phys_cpu_present_map and the logical/physical mappings.
+ * cpu_possible_map and the logical/physical mappings.
  * XXXKW will the boot CPU ever not be physical 0?
  *
  * Common setup before any secondaries are started
@@ -133,14 +133,14 @@ static void __init sb1250_smp_setup(void)
 {
 	int i, num;
 
-	cpus_clear(phys_cpu_present_map);
-	cpu_set(0, phys_cpu_present_map);
+	cpus_clear(cpu_possible_map);
+	cpu_set(0, cpu_possible_map);
 	__cpu_number_map[0] = 0;
 	__cpu_logical_map[0] = 0;
 
 	for (i = 1, num = 0; i < NR_CPUS; i++) {
 		if (cfe_cpu_stop(i) == 0) {
-			cpu_set(i, phys_cpu_present_map);
+			cpu_set(i, cpu_possible_map);
 			__cpu_number_map[i] = ++num;
 			__cpu_logical_map[num] = i;
 		}

arch/parisc/Kconfig

@@ -11,6 +11,7 @@ config PARISC
 	select HAVE_OPROFILE
 	select RTC_CLASS
 	select RTC_DRV_PARISC
+	select INIT_ALL_POSSIBLE
 	help
 	  The PA-RISC microprocessor is designed by Hewlett-Packard and used
 	  in many of their workstations & servers (HP9000 700 and 800 series,

arch/parisc/kernel/smp.c

@@ -67,21 +67,6 @@ static volatile int cpu_now_booting __read_mostly = 0;	/* track which CPU is boo
 
 static int parisc_max_cpus __read_mostly = 1;
 
-/* online cpus are ones that we've managed to bring up completely
- * possible cpus are all valid cpu 
- * present cpus are all detected cpu
- *
- * On startup we bring up the "possible" cpus. Since we discover
- * CPUs later, we add them as hotplug, so the possible cpu mask is
- * empty in the beginning.
- */
-
-cpumask_t cpu_online_map   __read_mostly = CPU_MASK_NONE;	/* Bitmap of online CPUs */
-cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL;	/* Bitmap of Present CPUs */
-
-EXPORT_SYMBOL(cpu_online_map);
-EXPORT_SYMBOL(cpu_possible_map);
-
 DEFINE_PER_CPU(spinlock_t, ipi_lock) = SPIN_LOCK_UNLOCKED;
 
 enum ipi_message_type {

arch/powerpc/kernel/smp.c

@@ -60,13 +60,9 @@
 int smp_hw_index[NR_CPUS];
 struct thread_info *secondary_ti;
 
-cpumask_t cpu_possible_map = CPU_MASK_NONE;
-cpumask_t cpu_online_map = CPU_MASK_NONE;
 DEFINE_PER_CPU(cpumask_t, cpu_sibling_map) = CPU_MASK_NONE;
 DEFINE_PER_CPU(cpumask_t, cpu_core_map) = CPU_MASK_NONE;
 
-EXPORT_SYMBOL(cpu_online_map);
-EXPORT_SYMBOL(cpu_possible_map);
 EXPORT_PER_CPU_SYMBOL(cpu_sibling_map);
 EXPORT_PER_CPU_SYMBOL(cpu_core_map);
 

arch/s390/Kconfig

@@ -75,6 +75,7 @@ config S390
 	select HAVE_KRETPROBES
 	select HAVE_KVM if 64BIT
 	select HAVE_ARCH_TRACEHOOK
+	select INIT_ALL_POSSIBLE
 
 source "init/Kconfig"
 

arch/s390/kernel/smp.c

@@ -52,12 +52,6 @@
 struct _lowcore *lowcore_ptr[NR_CPUS];
 EXPORT_SYMBOL(lowcore_ptr);
 
-cpumask_t cpu_online_map = CPU_MASK_NONE;
-EXPORT_SYMBOL(cpu_online_map);
-
-cpumask_t cpu_possible_map = CPU_MASK_ALL;
-EXPORT_SYMBOL(cpu_possible_map);
-
 static struct task_struct *current_set[NR_CPUS];
 
 static u8 smp_cpu_type;

arch/sh/kernel/smp.c

@@ -31,12 +31,6 @@
 int __cpu_number_map[NR_CPUS];		/* Map physical to logical */
 int __cpu_logical_map[NR_CPUS];		/* Map logical to physical */
 
-cpumask_t cpu_possible_map;
-EXPORT_SYMBOL(cpu_possible_map);
-
-cpumask_t cpu_online_map;
-EXPORT_SYMBOL(cpu_online_map);
-
 static inline void __init smp_store_cpu_info(unsigned int cpu)
 {
 	struct sh_cpuinfo *c = cpu_data + cpu;

arch/sparc/include/asm/smp_32.h

@@ -29,8 +29,6 @@
  */
 
 extern unsigned char boot_cpu_id;
-extern cpumask_t phys_cpu_present_map;
-#define cpu_possible_map phys_cpu_present_map
 
 typedef void (*smpfunc_t)(unsigned long, unsigned long, unsigned long,
 		       unsigned long, unsigned long);

arch/sparc/kernel/smp.c

@@ -39,8 +39,6 @@ volatile unsigned long cpu_callin_map[NR_CPUS] __cpuinitdata = {0,};
 unsigned char boot_cpu_id = 0;
 unsigned char boot_cpu_id4 = 0; /* boot_cpu_id << 2 */
 
-cpumask_t cpu_online_map = CPU_MASK_NONE;
-cpumask_t phys_cpu_present_map = CPU_MASK_NONE;
 cpumask_t smp_commenced_mask = CPU_MASK_NONE;
 
 /* The only guaranteed locking primitive available on all Sparc
@@ -334,7 +332,7 @@ void __init smp_setup_cpu_possible_map(void)
 	instance = 0;
 	while (!cpu_find_by_instance(instance, NULL, &mid)) {
 		if (mid < NR_CPUS) {
-			cpu_set(mid, phys_cpu_present_map);
+			cpu_set(mid, cpu_possible_map);
 			cpu_set(mid, cpu_present_map);
 		}
 		instance++;
@@ -354,7 +352,7 @@ void __init smp_prepare_boot_cpu(void)
 
 	current_thread_info()->cpu = cpuid;
 	cpu_set(cpuid, cpu_online_map);
-	cpu_set(cpuid, phys_cpu_present_map);
+	cpu_set(cpuid, cpu_possible_map);
 }
 
 int __cpuinit __cpu_up(unsigned int cpu)

arch/sparc/kernel/sparc_ksyms.c

@@ -113,10 +113,6 @@ EXPORT_PER_CPU_SYMBOL(__cpu_data);
 #ifdef CONFIG_SMP
 /* IRQ implementation. */
 EXPORT_SYMBOL(synchronize_irq);
-
-/* CPU online map and active count. */
-EXPORT_SYMBOL(cpu_online_map);
-EXPORT_SYMBOL(phys_cpu_present_map);
 #endif
 
 EXPORT_SYMBOL(__udelay);

arch/sparc64/kernel/smp.c

@@ -49,14 +49,10 @@
 
 int sparc64_multi_core __read_mostly;
 
-cpumask_t cpu_possible_map __read_mostly = CPU_MASK_NONE;
-cpumask_t cpu_online_map __read_mostly = CPU_MASK_NONE;
 DEFINE_PER_CPU(cpumask_t, cpu_sibling_map) = CPU_MASK_NONE;
 cpumask_t cpu_core_map[NR_CPUS] __read_mostly =
 	{ [0 ... NR_CPUS-1] = CPU_MASK_NONE };
 
-EXPORT_SYMBOL(cpu_possible_map);
-EXPORT_SYMBOL(cpu_online_map);
 EXPORT_PER_CPU_SYMBOL(cpu_sibling_map);
 EXPORT_SYMBOL(cpu_core_map);
 

arch/um/kernel/smp.c

@@ -25,13 +25,6 @@ DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
 #include "irq_user.h"
 #include "os.h"
 
-/* CPU online map, set by smp_boot_cpus */
-cpumask_t cpu_online_map = CPU_MASK_NONE;
-cpumask_t cpu_possible_map = CPU_MASK_NONE;
-
-EXPORT_SYMBOL(cpu_online_map);
-EXPORT_SYMBOL(cpu_possible_map);
-
 /* Per CPU bogomips and other parameters
  * The only piece used here is the ipi pipe, which is set before SMP is
  * started and never changed.

arch/x86/kernel/smpboot.c

@@ -101,14 +101,8 @@ EXPORT_SYMBOL(smp_num_siblings);
 /* Last level cache ID of each logical CPU */
 DEFINE_PER_CPU(u16, cpu_llc_id) = BAD_APICID;
 
-/* bitmap of online cpus */
-cpumask_t cpu_online_map __read_mostly;
-EXPORT_SYMBOL(cpu_online_map);
-
 cpumask_t cpu_callin_map;
 cpumask_t cpu_callout_map;
-cpumask_t cpu_possible_map;
-EXPORT_SYMBOL(cpu_possible_map);
 
 /* representing HT siblings of each logical CPU */
 DEFINE_PER_CPU(cpumask_t, cpu_sibling_map);

arch/x86/mach-voyager/voyager_smp.c

@@ -63,11 +63,6 @@ static int voyager_extended_cpus = 1;
 /* Used for the invalidate map that's also checked in the spinlock */
 static volatile unsigned long smp_invalidate_needed;
 
-/* Bitmask of currently online CPUs - used by setup.c for
-   /proc/cpuinfo, visible externally but still physical */
-cpumask_t cpu_online_map = CPU_MASK_NONE;
-EXPORT_SYMBOL(cpu_online_map);
-
 /* Bitmask of CPUs present in the system - exported by i386_syms.c, used
  * by scheduler but indexed physically */
 cpumask_t phys_cpu_present_map = CPU_MASK_NONE;
@@ -218,8 +213,6 @@ static cpumask_t smp_commenced_mask = CPU_MASK_NONE;
 /* This is for the new dynamic CPU boot code */
 cpumask_t cpu_callin_map = CPU_MASK_NONE;
 cpumask_t cpu_callout_map = CPU_MASK_NONE;
-cpumask_t cpu_possible_map = CPU_MASK_NONE;
-EXPORT_SYMBOL(cpu_possible_map);
 
 /* The per processor IRQ masks (these are usually kept in sync) */
 static __u16 vic_irq_mask[NR_CPUS] __cacheline_aligned;

include/asm-m32r/smp.h

@@ -63,8 +63,6 @@ extern volatile int cpu_2_physid[NR_CPUS];
 #define raw_smp_processor_id()	(current_thread_info()->cpu)
 
 extern cpumask_t cpu_callout_map;
-extern cpumask_t cpu_possible_map;
-extern cpumask_t cpu_present_map;
 
 static __inline__ int hard_smp_processor_id(void)
 {

init/Kconfig

@@ -916,6 +916,15 @@ config KMOD
 
 endif # MODULES
 
+config INIT_ALL_POSSIBLE
+	bool
+	help
+	  Back when each arch used to define their own cpu_online_map and
+	  cpu_possible_map, some of them chose to initialize cpu_possible_map
+	  with all 1s, and others with all 0s.  When they were centralised,
+	  it was better to provide this option than to break all the archs
+	  and have several arch maintainers persuing me down dark alleys.
+
 config STOP_MACHINE
 	bool
 	default y

kernel/cpu.c

@@ -24,19 +24,20 @@
 cpumask_t cpu_present_map __read_mostly;
 EXPORT_SYMBOL(cpu_present_map);
 
-#ifndef CONFIG_SMP
-
 /*
  * Represents all cpu's that are currently online.
  */
-cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL;
+cpumask_t cpu_online_map __read_mostly;
 EXPORT_SYMBOL(cpu_online_map);
 
+#ifdef CONFIG_INIT_ALL_POSSIBLE
 cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL;
+#else
+cpumask_t cpu_possible_map __read_mostly;
+#endif
 EXPORT_SYMBOL(cpu_possible_map);
 
-#else /* CONFIG_SMP */
-
+#ifdef CONFIG_SMP
 /* Serializes the updates to cpu_online_map, cpu_present_map */
 static DEFINE_MUTEX(cpu_add_remove_lock);