[PATCH v27 07/10] sched/core: Reset the donor to current task when donor is woken

[John Stultz]

From: K Prateek Nayak <kprateek.nayak@xxxxxxx>

Introduce proxy_reset_donor() to reset the donor to current task when
the donor is woken up.

This avoids needing to run with rq->idle as the donor when
proxy_needs_return() hits the donor which can result in another
different set of headaches.

Signed-off-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>
---
XXX: Confirm with Juri if there is any side-effect of temporarily
doing a set_next_task() on a throttled DL task.

Cc: Joel Fernandes <joelagnelf@xxxxxxxxxx>
Cc: Qais Yousef <qyousef@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Zimuzo Ezeozue <zezeozue@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Metin Kaya <Metin.Kaya@xxxxxxx>
Cc: Xuewen Yan <xuewen.yan94@xxxxxxxxx>
Cc: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: Suleiman Souhlal <suleiman@xxxxxxxxxx>
Cc: kuyo chang <kuyo.chang@xxxxxxxxxxxx>
Cc: hupu <hupu.gm@xxxxxxxxx>
Cc: kernel-team@xxxxxxxxxxx
---
 kernel/sched/core.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2b5f9f905afe1..a0d55225a62c3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3660,7 +3660,17 @@ void update_rq_avg_idle(struct rq *rq)
 }
 
 #ifdef CONFIG_SCHED_PROXY_EXEC
-static inline struct task_struct *proxy_resched_idle(struct rq *rq);
+static void zap_balance_callbacks(struct rq *rq);
+
+static inline void proxy_reset_donor(struct rq *rq)
+{
+	WARN_ON_ONCE(rq->donor == rq->curr);
+
+	put_prev_set_next_task(rq, rq->donor, rq->curr);
+	rq_set_donor(rq, rq->curr);
+	zap_balance_callbacks(rq);
+	resched_curr(rq);
+}
 
 /*
  * Checks to see if task p has been proxy-migrated to another rq
@@ -3685,7 +3695,7 @@ static inline bool proxy_needs_return(struct rq *rq, struct task_struct *p)
 
 	/* If we're return migrating the rq->donor, switch it out for idle */
 	if (task_current_donor(rq, p))
-		proxy_resched_idle(rq);
+		proxy_reset_donor(rq);
 
 	block_task(rq, p, TASK_WAKING);
 	return true;
-- 
2.53.0.1213.gd9a14994de-goog