[PATCH] Fix CPU Hotplug: neaten migrate_all_tasks.

A followup patch wants to do forced migration, so separate that part of the
code out of migrate_all_tasks().

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/sched.c b/kernel/sched.c
index 0b415e7b429dfe9b3556c2b2c34021db76a042d9..732344a7be1b2f8fe04245122e1c7674c0e70321 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3957,50 +3957,52 @@ wait_to_die:
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
+/* Figure out where task on dead CPU should go, use force if neccessary. */
+static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *tsk)
+{
+       int dest_cpu;
+       cpumask_t mask;
+
+       /* On same node? */
+       mask = node_to_cpumask(cpu_to_node(dead_cpu));
+       cpus_and(mask, mask, tsk->cpus_allowed);
+       dest_cpu = any_online_cpu(mask);
+
+       /* On any allowed CPU? */
+       if (dest_cpu == NR_CPUS)
+               dest_cpu = any_online_cpu(tsk->cpus_allowed);
+
+       /* No more Mr. Nice Guy. */
+       if (dest_cpu == NR_CPUS) {
+               cpus_setall(tsk->cpus_allowed);
+               dest_cpu = any_online_cpu(tsk->cpus_allowed);
+
+               /*
+                * Don't tell them about moving exiting tasks or
+                * kernel threads (both mm NULL), since they never
+                * leave kernel.
+                */
+               if (tsk->mm && printk_ratelimit())
+                       printk(KERN_INFO "process %d (%s) no "
+                              "longer affine to cpu%d\n",
+                              tsk->pid, tsk->comm, dead_cpu);
+       }
+       __migrate_task(tsk, dead_cpu, dest_cpu);
+}
+
 /* migrate_all_tasks - function to migrate all tasks from the dead cpu. */
 static void migrate_all_tasks(int src_cpu)
 {
        struct task_struct *tsk, *t;
-       int dest_cpu;
-       unsigned int node;
 
        write_lock_irq(&tasklist_lock);
 
-       /* watch out for per node tasks, let's stay on this node */
-       node = cpu_to_node(src_cpu);
-
        do_each_thread(t, tsk) {
-               cpumask_t mask;
                if (tsk == current)
                        continue;
 
-               if (task_cpu(tsk) != src_cpu)
-                       continue;
-
-               /* Figure out where this task should go (attempting to
-                * keep it on-node), and check if it can be migrated
-                * as-is.  NOTE that kernel threads bound to more than
-                * one online cpu will be migrated. */
-               mask = node_to_cpumask(node);
-               cpus_and(mask, mask, tsk->cpus_allowed);
-               dest_cpu = any_online_cpu(mask);
-               if (dest_cpu == NR_CPUS)
-                       dest_cpu = any_online_cpu(tsk->cpus_allowed);
-               if (dest_cpu == NR_CPUS) {
-                       cpus_setall(tsk->cpus_allowed);
-                       dest_cpu = any_online_cpu(tsk->cpus_allowed);
-
-                       /*
-                        * Don't tell them about moving exiting tasks
-                        * or kernel threads (both mm NULL), since
-                        * they never leave kernel.
-                        */
-                       if (tsk->mm && printk_ratelimit())
-                               printk(KERN_INFO "process %d (%s) no "
-                                      "longer affine to cpu%d\n",
-                                      tsk->pid, tsk->comm, src_cpu);
-               }
-               __migrate_task(tsk, src_cpu, dest_cpu);
+               if (task_cpu(tsk) == src_cpu)
+                       move_task_off_dead_cpu(src_cpu, tsk);
        } while_each_thread(t, tsk);
 
        write_unlock_irq(&tasklist_lock);