sched: Remove need_migrate_task()

Oleg noticed that need_migrate_task() doesn't need the ->on_cpu check
now that ttwu() doesn't do remote enqueues for !->on_rq && ->on_cpu,
so remove the helper and replace the single instance with a direct
->on_rq test.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Frank Rowand <frank.rowand@am.sony.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20110405152729.556674812@chello.nl
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 9e3ede1..cd597c7 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2198,21 +2198,6 @@ struct migration_arg {
 
 static int migration_cpu_stop(void *data);
 
-/*
- * The task's runqueue lock must be held.
- * Returns true if you have to wait for migration thread.
- */
-static bool need_migrate_task(struct task_struct *p)
-{
-       /*
-        * If the task is not on a runqueue (and not running), then
-        * the next wake-up will properly place the task.
-        */
-       bool running = p->on_rq || p->on_cpu;
-       smp_rmb(); /* finish_lock_switch() */
-       return running;
-}
-
 /*
  * wait_task_inactive - wait for a thread to unschedule.
  *
@@ -5985,7 +5970,7 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
                goto out;
 
        dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
-       if (need_migrate_task(p)) {
+       if (p->on_rq) {
                struct migration_arg arg = { p, dest_cpu };
                /* Need help from migration thread: drop lock and wait. */
                task_rq_unlock(rq, p, &flags);