add per_cpu_dyn_array support

allow dyn-array in per_cpu area, allocated dynamically.

usage:

|  /* in .h */
| struct kernel_stat {
|        struct cpu_usage_stat   cpustat;
|        unsigned int *irqs;
| };
|
|  /* in .c */
| DEFINE_PER_CPU(struct kernel_stat, kstat);
|
| DEFINE_PER_CPU_DYN_ARRAY_ADDR(per_cpu__kstat_irqs, per_cpu__kstat.irqs, sizeof(unsigned int), nr_irqs, sizeof(unsigned long), NULL);

after setup_percpu()/per_cpu_alloc_dyn_array(), the dyn_array in
per_cpu area is ready to use.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 0e67f72..13ba7a8 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -140,7 +140,7 @@
  */
 void __init setup_per_cpu_areas(void)
 {
-	ssize_t size = PERCPU_ENOUGH_ROOM;
+	ssize_t size, old_size;
 	char *ptr;
 	int cpu;
 
@@ -148,7 +148,8 @@
 	setup_cpu_pda_map();
 
 	/* Copy section for each CPU (we discard the original) */
-	size = PERCPU_ENOUGH_ROOM;
+	old_size = PERCPU_ENOUGH_ROOM;
+	size = old_size + per_cpu_dyn_array_size();
 	printk(KERN_INFO "PERCPU: Allocating %zd bytes of per cpu data\n",
 			  size);
 
@@ -176,6 +177,8 @@
 		per_cpu_offset(cpu) = ptr - __per_cpu_start;
 		memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start);
 
+		per_cpu_alloc_dyn_array(cpu, ptr + old_size);
+
 	}
 
 	printk(KERN_DEBUG "NR_CPUS: %d, nr_cpu_ids: %d, nr_node_ids %d\n",