sched: Drop rq->lock from first part of wake_up_new_task()

Since p->pi_lock now protects all things needed to call
select_task_rq() avoid the double remote rq->lock acquisition and rely
on p->pi_lock.

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/20110405152729.273362517@chello.nl
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 14 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index f1551271a685..7c5494dccd39 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2736,28 +2736,18 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
 {
         unsigned long flags;
         struct rq *rq;
-        int cpu __maybe_unused = get_cpu();
 
+        raw_spin_lock_irqsave(&p->pi_lock, flags);
 #ifdef CONFIG_SMP
-        rq = task_rq_lock(p, &flags);
-        p->state = TASK_WAKING;
-
         /*
          * Fork balancing, do it here and not earlier because:
          *  - cpus_allowed can change in the fork path
          *  - any previously selected cpu might disappear through hotplug
-         *
-         * We set TASK_WAKING so that select_task_rq() can drop rq->lock
-         * without people poking at ->cpus_allowed.
          */
-        cpu = select_task_rq(p, SD_BALANCE_FORK, 0);
-        set_task_cpu(p, cpu);
-
-        p->state = TASK_RUNNING;
-        task_rq_unlock(rq, p, &flags);
+        set_task_cpu(p, select_task_rq(p, SD_BALANCE_FORK, 0));
 #endif
 
-        rq = task_rq_lock(p, &flags);
+        rq = __task_rq_lock(p);
         activate_task(rq, p, 0);
         p->on_rq = 1;
         trace_sched_wakeup_new(p, true);
@@ -2767,7 +2757,6 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
                 p->sched_class->task_woken(rq, p);
 #endif
         task_rq_unlock(rq, p, &flags);
-        put_cpu();
 }
 
 #ifdef CONFIG_PREEMPT_NOTIFIERS