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Commit 72465447 authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Ingo Molnar
Browse files

sched, nohz: Change rq->nr_running to always use wrappers 



Sometimes ->nr_running may cross 2 but interrupt is not being
sent to rq's cpu. In this case we don't reenable the timer.
Looks like this may be the reason for rare unexpected effects,
if nohz is enabled.

Patch replaces all places of direct changing of nr_running
and makes add_nr_running() caring about crossing border.

Signed-off-by: default avatarKirill Tkhai <tkhai@yandex.ru>
Acked-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140508225830.2469.97461.stgit@localhost


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 52a08ef1

kernel/sched/deadline.c

+2 −2
Original line number Diff line number Diff line
@@ -741,7 +741,7 @@ void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq) 


	WARN_ON(!dl_prio(prio));

	dl_rq->dl_nr_running++;

	inc_nr_running(rq_of_dl_rq(dl_rq));

	add_nr_running(rq_of_dl_rq(dl_rq), 1);



	inc_dl_deadline(dl_rq, deadline);

	inc_dl_migration(dl_se, dl_rq);
@@ -755,7 +755,7 @@ void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq) 
	WARN_ON(!dl_prio(prio));

	WARN_ON(!dl_rq->dl_nr_running);

	dl_rq->dl_nr_running--;

	dec_nr_running(rq_of_dl_rq(dl_rq));

	sub_nr_running(rq_of_dl_rq(dl_rq), 1);



	dec_dl_deadline(dl_rq, dl_se->deadline);

	dec_dl_migration(dl_se, dl_rq);

kernel/sched/fair.c

+4 −4
Original line number Diff line number Diff line
@@ -3325,7 +3325,7 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq) 
	}



	if (!se)

		rq->nr_running -= task_delta;

		sub_nr_running(rq, task_delta);



	cfs_rq->throttled = 1;

	cfs_rq->throttled_clock = rq_clock(rq);
@@ -3376,7 +3376,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) 
	}



	if (!se)

		rq->nr_running += task_delta;

		add_nr_running(rq, task_delta);



	/* determine whether we need to wake up potentially idle cpu */

	if (rq->curr == rq->idle && rq->cfs.nr_running)
@@ -3908,7 +3908,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 


	if (!se) {

		update_rq_runnable_avg(rq, rq->nr_running);

		inc_nr_running(rq);

		add_nr_running(rq, 1);

	}

	hrtick_update(rq);

}
@@ -3968,7 +3968,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
	}



	if (!se) {

		dec_nr_running(rq);

		sub_nr_running(rq, 1);

		update_rq_runnable_avg(rq, 1);

	}

	hrtick_update(rq);

kernel/sched/rt.c

+2 −2
Original line number Diff line number Diff line
@@ -973,7 +973,7 @@ dequeue_top_rt_rq(struct rt_rq *rt_rq) 


	BUG_ON(!rq->nr_running);



	rq->nr_running -= rt_rq->rt_nr_running;

	sub_nr_running(rq, rt_rq->rt_nr_running);

	rt_rq->rt_queued = 0;

}
@@ -989,7 +989,7 @@ enqueue_top_rt_rq(struct rt_rq *rt_rq) 
	if (rt_rq_throttled(rt_rq) || !rt_rq->rt_nr_running)

		return;



	rq->nr_running += rt_rq->rt_nr_running;

	add_nr_running(rq, rt_rq->rt_nr_running);

	rt_rq->rt_queued = 1;

}

kernel/sched/sched.h

+7 −5
Original line number Diff line number Diff line
@@ -1206,12 +1206,14 @@ extern void update_idle_cpu_load(struct rq *this_rq); 


extern void init_task_runnable_average(struct task_struct *p);



static inline void inc_nr_running(struct rq *rq)

static inline void add_nr_running(struct rq *rq, unsigned count)

{

	rq->nr_running++;

	unsigned prev_nr = rq->nr_running;



	rq->nr_running = prev_nr + count;



#ifdef CONFIG_NO_HZ_FULL

	if (rq->nr_running == 2) {

	if (prev_nr < 2 && rq->nr_running >= 2) {

		if (tick_nohz_full_cpu(rq->cpu)) {

			/* Order rq->nr_running write against the IPI */

			smp_wmb();
@@ -1221,9 +1223,9 @@ static inline void inc_nr_running(struct rq *rq) 
#endif

}



static inline void dec_nr_running(struct rq *rq)

static inline void sub_nr_running(struct rq *rq, unsigned count)

{

	rq->nr_running--;

	rq->nr_running -= count;

}



static inline void rq_last_tick_reset(struct rq *rq)

kernel/sched/stop_task.c

+2 −2
Original line number Diff line number Diff line
@@ -41,13 +41,13 @@ pick_next_task_stop(struct rq *rq, struct task_struct *prev) 
static void

enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)

{

	inc_nr_running(rq);

	add_nr_running(rq, 1);

}



static void

dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)

{

	dec_nr_running(rq);

	sub_nr_running(rq, 1);

}



static void yield_task_stop(struct rq *rq)