[PATCH] node hotplug: register cpu: remove node struct

With Goto-san's patch, we can add new pgdat/node at runtime.  I'm now
considering node-hot-add with cpu + memory on ACPI.

I found acpi container, which describes node, could evaluate cpu before
memory. This means cpu-hot-add occurs before memory hot add.

In most part, cpu-hot-add doesn't depend on node hot add.  But register_cpu(),
which creates symbolic link from node to cpu, requires that node should be
onlined before register_cpu().  When a node is onlined, its pgdat should be
there.

This patch-set holds off creating symbolic link from node to cpu
until node is onlined.

This removes node arguments from register_cpu().

Now, register_cpu() requires 'struct node' as its argument.  But the array of
struct node is now unified in driver/base/node.c now (By Goto's node hotplug
patch).  We can get struct node in generic way.  So, this argument is not
necessary now.

This patch also guarantees add cpu under node only when node is onlined.  It
is necessary for node-hot-add vs.  cpu-hot-add patch following this.

Moreover, register_cpu calculates cpu->node_id by cpu_to_node() without regard
to its 'struct node *root' argument.  This patch removes it.

Also modify callers of register_cpu()/unregister_cpu, whose args are changed
by register-cpu-remove-node-struct patch.

[Brice.Goglin@ens-lyon.org: fix it]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Brice Goglin <Brice.Goglin@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 44 insertions, 10 deletions

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index dd712b24ec91..3972d8ac9786 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -8,6 +8,7 @@
 #include <linux/cpu.h>
 #include <linux/topology.h>
 #include <linux/device.h>
+#include <linux/node.h>
 
 #include "base.h"
 
@@ -57,13 +58,12 @@ static void __devinit register_cpu_control(struct cpu *cpu)
 {
         sysdev_create_file(&cpu->sysdev, &attr_online);
 }
-void unregister_cpu(struct cpu *cpu, struct node *root)
+void unregister_cpu(struct cpu *cpu)
 {
         int logical_cpu = cpu->sysdev.id;
 
-        if (root)
-                sysfs_remove_link(&root->sysdev.kobj,
-                                  kobject_name(&cpu->sysdev.kobj));
+        unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
+
         sysdev_remove_file(&cpu->sysdev, &attr_online);
 
         sysdev_unregister(&cpu->sysdev);
@@ -109,23 +109,21 @@ static SYSDEV_ATTR(crash_notes, 0400, show_crash_notes, NULL);
  *
  * Initialize and register the CPU device.
  */
-int __devinit register_cpu(struct cpu *cpu, int num, struct node *root)
+int __devinit register_cpu(struct cpu *cpu, int num)
 {
         int error;
-
         cpu->node_id = cpu_to_node(num);
         cpu->sysdev.id = num;
         cpu->sysdev.cls = &cpu_sysdev_class;
 
         error = sysdev_register(&cpu->sysdev);
-        if (!error && root)
-                error = sysfs_create_link(&root->sysdev.kobj,
-                                          &cpu->sysdev.kobj,
-                                          kobject_name(&cpu->sysdev.kobj));
+
         if (!error && !cpu->no_control)
                 register_cpu_control(cpu);
         if (!error)
                 cpu_sys_devices[num] = &cpu->sysdev;
+        if (!error)
+                register_cpu_under_node(num, cpu_to_node(num));
 
 #ifdef CONFIG_KEXEC
         if (!error)
diff --git a/drivers/base/node.c b/drivers/base/node.c
index cbd0f62b4870..eae2bdc183bb 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -11,6 +11,7 @@
 #include <linux/cpumask.h>
 #include <linux/topology.h>
 #include <linux/nodemask.h>
+#include <linux/cpu.h>
 
 static struct sysdev_class node_class = {
         set_kset_name("node"),
@@ -192,9 +193,38 @@ void unregister_node(struct node *node)
 
 struct node node_devices[MAX_NUMNODES];
 
+/*
+ * register cpu under node
+ */
+int register_cpu_under_node(unsigned int cpu, unsigned int nid)
+{
+        if (node_online(nid)) {
+                struct sys_device *obj = get_cpu_sysdev(cpu);
+                if (!obj)
+                        return 0;
+                return sysfs_create_link(&node_devices[nid].sysdev.kobj,
+                                         &obj->kobj,
+                                         kobject_name(&obj->kobj));
+         }
+
+        return 0;
+}
+
+int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
+{
+        if (node_online(nid)) {
+                struct sys_device *obj = get_cpu_sysdev(cpu);
+                if (obj)
+                        sysfs_remove_link(&node_devices[nid].sysdev.kobj,
+                                         kobject_name(&obj->kobj));
+        }
+        return 0;
+}
+
 int register_one_node(int nid)
 {
         int error = 0;
+        int cpu;
 
         if (node_online(nid)) {
                 int p_node = parent_node(nid);
@@ -204,6 +234,12 @@ int register_one_node(int nid)
                         parent = &node_devices[p_node];
 
                 error = register_node(&node_devices[nid], nid, parent);
+
+                /* link cpu under this node */
+                for_each_present_cpu(cpu) {
+                        if (cpu_to_node(cpu) == nid)
+                                register_cpu_under_node(cpu, nid);
+                }
         }
 
         return error;