linux-kernel - [PATCH 2/7] sched/fair: Better document newidle

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Date:   Fri, 08 Nov 2019 14:15:55 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     mingo@...nel.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, juri.lelli@...hat.com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de
Cc:     linux-kernel@...r.kernel.org, qperret@...gle.com,
        valentin.schneider@....com, qais.yousef@....com,
        ktkhai@...tuozzo.com, peterz@...radead.org
Subject: [PATCH 2/7] sched/fair: Better document newidle_balance()

Whilst chasing the pick_next_task() race, there was some confusion
about the newidle_balance() return values. Document them.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/sched/fair.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9920,6 +9920,11 @@ static inline void nohz_newidle_balance(
 /*
  * idle_balance is called by schedule() if this_cpu is about to become
  * idle. Attempts to pull tasks from other CPUs.
+ *
+ * Returns:
+ *  <0 - we released the lock and there are !fair tasks present
+ *   0 - failed, no new tasks
+ *  >0 - success, new (fair) tasks present
  */
 int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
 {