[PATCH] cpumask: make cpu_present_map real even on non-smp

From: Paul Jackson <pj@sgi.com>

This patch makes cpu_present_map a real map for all configurations, instead of
a constant for non-SMP.  It also moves the definition of cpu_present_map out
of kernel/cpu.c into kernel/sched.c, because cpu.c isn't compiled into non-SMP
kernels.

The pattern is that each of the possible, present and online cpu maps are
actual kernel global cpumask_t variables, for all configurations.  They are
documented in include/linux/cpumask.h.  Some of the UP (NR_CPUS=1) code
cheats, and hardcodes the assumption that the single bit position of these
maps is always set, as an optimization.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/cpumask.h

@@ -10,15 +10,12 @@
 
 extern cpumask_t cpu_online_map;
 extern cpumask_t cpu_possible_map;
-extern cpumask_t cpu_present_map;
 
 #define num_online_cpus()		cpus_weight(cpu_online_map)
 #define num_possible_cpus()		cpus_weight(cpu_possible_map)
-#define num_present_cpus()		cpus_weight(cpu_present_map)
 
 #define cpu_online(cpu)			cpu_isset(cpu, cpu_online_map)
 #define cpu_possible(cpu)		cpu_isset(cpu, cpu_possible_map)
-#define cpu_present(cpu)		cpu_isset(cpu, cpu_present_map)
 
 #define for_each_cpu_mask(cpu, mask)					\
 	for (cpu = first_cpu_const(mk_cpumask_const(mask));		\
@@ -27,26 +24,26 @@ extern cpumask_t cpu_present_map;
 
 #define for_each_cpu(cpu) for_each_cpu_mask(cpu, cpu_possible_map)
 #define for_each_online_cpu(cpu) for_each_cpu_mask(cpu, cpu_online_map)
-#define for_each_present_cpu(cpu) for_each_cpu_mask(cpu, cpu_present_map)
 #else
 #define	cpu_online_map			cpumask_of_cpu(0)
 #define	cpu_possible_map		cpumask_of_cpu(0)
-#define	cpu_present_map			cpumask_of_cpu(0)
 
 #define num_online_cpus()		1
 #define num_possible_cpus()		1
-#define num_present_cpus()		1
 
 #define cpu_online(cpu)			({ BUG_ON((cpu) != 0); 1; })
 #define cpu_possible(cpu)		({ BUG_ON((cpu) != 0); 1; })
-#define cpu_present(cpu)		({ BUG_ON((cpu) != 0); 1; })
 
 #define for_each_cpu_mask(cpu, mask) for (cpu = 0; cpu < 1; cpu++)
 #define for_each_cpu(cpu) for (cpu = 0; cpu < 1; cpu++)
 #define for_each_online_cpu(cpu) for (cpu = 0; cpu < 1; cpu++)
-#define for_each_present_cpu(cpu) for (cpu = 0; cpu < 1; cpu++)
 #endif
 
+extern cpumask_t cpu_present_map;
+#define num_present_cpus()		cpus_weight(cpu_present_map)
+#define cpu_present(cpu)		cpu_isset(cpu, cpu_present_map)
+#define for_each_present_cpu(cpu)	for_each_cpu_mask(cpu, cpu_present_map)
+
 #define cpumask_scnprintf(buf, buflen, map)				\
 	bitmap_scnprintf(buf, buflen, cpus_addr(map), NR_CPUS)
 

kernel/cpu.c

@@ -20,14 +20,6 @@
 DECLARE_MUTEX(cpucontrol);
 
 static struct notifier_block *cpu_chain;
-/*
- * Represents all cpu's present in the system
- * In systems capable of hotplug, this map could dynamically grow
- * as new cpu's are detected in the system via any platform specific
- * method, such as ACPI for e.g.
- */
-cpumask_t	cpu_present_map;
-EXPORT_SYMBOL(cpu_present_map);
 
 /* Need to know about CPUs going up/down? */
 int register_cpu_notifier(struct notifier_block *nb)

kernel/sched.c

@@ -2941,6 +2941,16 @@ asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
 	return retval;
 }
 
+/*
+ * Represents all cpu's present in the system
+ * In systems capable of hotplug, this map could dynamically grow
+ * as new cpu's are detected in the system via any platform specific
+ * method, such as ACPI for e.g.
+ */
+
+cpumask_t cpu_present_map;
+EXPORT_SYMBOL(cpu_present_map);
+
 /**
  * sys_sched_getaffinity - get the cpu affinity of a process
  * @pid: pid of the process