[RFC][PATCH 12/18] sched: Drop rq->lock from first part of wake_up_new_task()

[Peter Zijlstra]

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.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 kernel/sched.c |   20 +++++---------------
 1 file changed, 5 insertions(+), 15 deletions(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -2681,28 +2681,18 @@ void wake_up_new_task(struct task_struct
 {
 	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, &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);
 	trace_sched_wakeup_new(p, true);
 	check_preempt_curr(rq, p, WF_FORK);
@@ -2710,8 +2700,8 @@ void wake_up_new_task(struct task_struct
 	if (p->sched_class->task_woken)
 		p->sched_class->task_woken(rq, p);
 #endif
-	task_rq_unlock(rq, &flags);
-	put_cpu();
+	__task_rq_unlock(rq);
+	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
 }
 
 #ifdef CONFIG_PREEMPT_NOTIFIERS


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/