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Subject[RFC][PATCH 2/3] sched, workqueue: Move WQ-sleeper wakeup
While Thomas was annoyed with the block bits, he found no reason for the WQ
bits to be as they are, the signal thing can only avoid a wakeup, extra wakeups
for the WQ bits increase concurrency (in as far as signals are relevant to
kthreads at all).

Moving the WQ bits allow us to do away with try_to_wake_up_local, removing
more lines.

Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/sched.c | 60 ++++++++++++---------------------------------------------
1 file changed, 13 insertions(+), 47 deletions(-)
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -2703,40 +2703,6 @@ try_to_wake_up(struct task_struct *p, un
}

/**
- * try_to_wake_up_local - try to wake up a local task with rq lock held
- * @p: the thread to be awakened
- *
- * Put @p on the run-queue if it's not already there. The caller must
- * ensure that this_rq() is locked, @p is bound to this_rq() and not
- * the current task.
- */
-static void try_to_wake_up_local(struct task_struct *p)
-{
- struct rq *rq = task_rq(p);
-
- BUG_ON(rq != this_rq());
- BUG_ON(p == current);
- lockdep_assert_held(&rq->lock);
-
- if (!raw_spin_trylock(&p->pi_lock)) {
- raw_spin_unlock(&rq->lock);
- raw_spin_lock(&p->pi_lock);
- raw_spin_lock(&rq->lock);
- }
-
- if (!(p->state & TASK_NORMAL))
- goto out;
-
- if (!p->on_rq)
- ttwu_activate(rq, p, ENQUEUE_WAKEUP);
-
- ttwu_do_wakeup(rq, p, 0);
- ttwu_stat(p, smp_processor_id(), 0);
-out:
- raw_spin_unlock(&p->pi_lock);
-}
-
-/**
* wake_up_process - Wake up a specific process
* @p: The process to be woken up.
*
@@ -4215,6 +4181,19 @@ static inline void sched_submit_work(voi

if (tsk->state && !(preempt_count() & PREEMPT_ACTIVE)) {
/*
+ * If a worker went to sleep, notify and ask workqueue
+ * whether it wants to wake up a task to maintain
+ * concurrency.
+ */
+ if (tsk->flags & PF_WQ_WORKER) {
+ struct task_struct *to_wakeup;
+
+ to_wakeup = wq_worker_sleeping(tsk, smp_processor_id());
+ if (to_wakeup)
+ wake_up_process(to_wakeup);
+ }
+
+ /*
* If we are going to sleep and we have plugged IO
* queued, make sure to submit it to avoid deadlocks.
*/
@@ -4256,19 +4235,6 @@ asmlinkage void __sched schedule(void)
} else {
deactivate_task(rq, prev, DEQUEUE_SLEEP);
prev->on_rq = 0;
-
- /*
- * If a worker went to sleep, notify and ask workqueue
- * whether it wants to wake up a task to maintain
- * concurrency.
- */
- if (prev->flags & PF_WQ_WORKER) {
- struct task_struct *to_wakeup;
-
- to_wakeup = wq_worker_sleeping(prev, cpu);
- if (to_wakeup)
- try_to_wake_up_local(to_wakeup);
- }
}
switch_count = &prev->nvcsw;
}



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