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Date: Thu, 14 Apr 2011 08:39:28 GMT
From: tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
torvalds@...ux-foundation.org, a.p.zijlstra@...llo.nl,
efault@....de, npiggin@...nel.dk, akpm@...ux-foundation.org,
tglx@...utronix.de, frank.rowand@...sony.com, mingo@...e.hu
Subject: [tip:sched/locking] sched: Restructure ttwu() some more
Commit-ID: c05fbafba1c5482bee399b360288fa405415e126
Gitweb: http://git.kernel.org/tip/c05fbafba1c5482bee399b360288fa405415e126
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Tue, 5 Apr 2011 17:23:57 +0200
Committer: Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 14 Apr 2011 08:52:40 +0200
sched: Restructure ttwu() some more
Factor our helper functions to make the inner workings of try_to_wake_up()
more obvious, this also allows for adding remote queues.
Reviewed-by: Frank Rowand <frank.rowand@...sony.com>
Cc: Mike Galbraith <efault@....de>
Cc: Nick Piggin <npiggin@...nel.dk>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/20110405152729.475848012@chello.nl
---
kernel/sched.c | 91 +++++++++++++++++++++++++++++++++++--------------------
1 files changed, 58 insertions(+), 33 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index e309dba..7d8b85f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2483,6 +2483,48 @@ ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
#endif
}
+static void
+ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags)
+{
+#ifdef CONFIG_SMP
+ if (p->sched_contributes_to_load)
+ rq->nr_uninterruptible--;
+#endif
+
+ ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING);
+ ttwu_do_wakeup(rq, p, wake_flags);
+}
+
+/*
+ * Called in case the task @p isn't fully descheduled from its runqueue,
+ * in this case we must do a remote wakeup. Its a 'light' wakeup though,
+ * since all we need to do is flip p->state to TASK_RUNNING, since
+ * the task is still ->on_rq.
+ */
+static int ttwu_remote(struct task_struct *p, int wake_flags)
+{
+ struct rq *rq;
+ int ret = 0;
+
+ rq = __task_rq_lock(p);
+ if (p->on_rq) {
+ ttwu_do_wakeup(rq, p, wake_flags);
+ ret = 1;
+ }
+ __task_rq_unlock(rq);
+
+ return ret;
+}
+
+static void ttwu_queue(struct task_struct *p, int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ raw_spin_lock(&rq->lock);
+ ttwu_do_activate(rq, p, 0);
+ raw_spin_unlock(&rq->lock);
+}
+
/**
* try_to_wake_up - wake up a thread
* @p: the thread to be awakened
@@ -2501,27 +2543,25 @@ ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
static int
try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
{
- int cpu, this_cpu, success = 0;
unsigned long flags;
- struct rq *rq;
-
- this_cpu = get_cpu();
+ int cpu, success = 0;
smp_wmb();
raw_spin_lock_irqsave(&p->pi_lock, flags);
if (!(p->state & state))
goto out;
+ success = 1; /* we're going to change ->state */
cpu = task_cpu(p);
- if (p->on_rq) {
- rq = __task_rq_lock(p);
- if (p->on_rq)
- goto out_running;
- __task_rq_unlock(rq);
- }
+ if (p->on_rq && ttwu_remote(p, wake_flags))
+ goto stat;
#ifdef CONFIG_SMP
+ /*
+ * If the owning (remote) cpu is still in the middle of schedule() with
+ * this task as prev, wait until its done referencing the task.
+ */
while (p->on_cpu) {
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
/*
@@ -2530,8 +2570,10 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
* to spin on ->on_cpu if p is current, since that would
* deadlock.
*/
- if (p == current)
- goto out_activate;
+ if (p == current) {
+ ttwu_queue(p, cpu);
+ goto stat;
+ }
#endif
cpu_relax();
}
@@ -2547,32 +2589,15 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
p->sched_class->task_waking(p);
cpu = select_task_rq(p, SD_BALANCE_WAKE, wake_flags);
-#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
-out_activate:
-#endif
-#endif /* CONFIG_SMP */
-
- rq = cpu_rq(cpu);
- raw_spin_lock(&rq->lock);
-
-#ifdef CONFIG_SMP
- if (cpu != task_cpu(p))
+ if (task_cpu(p) != cpu)
set_task_cpu(p, cpu);
+#endif /* CONFIG_SMP */
- if (p->sched_contributes_to_load)
- rq->nr_uninterruptible--;
-#endif
-
- ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING);
-out_running:
- ttwu_do_wakeup(rq, p, wake_flags);
- success = 1;
- __task_rq_unlock(rq);
-
+ ttwu_queue(p, cpu);
+stat:
ttwu_stat(p, cpu, wake_flags);
out:
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
- put_cpu();
return success;
}
--
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