[RFC][PATCH 3/5] sched/core: Reset RQCF_ACT_SKIP before unpinning rq->lock

Matt Fleming
2016-05-12T19:50:52Z

rq_clock() is called from sched_info_{depart,arrive}() after resetting
RQCF_ACT_SKIP but prior to a call to update_rq_clock().

In preparation for pending patches that check whether the rq clock has
been updated inside of a pin context before rq_clock() is called, move
the reset of rq->clock_skip_update immediately before unpinning the rq
lock.

This will avoid the new warnings which check if update_rq_clock() is
being actively skipped.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
---
kernel/sched/core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index dfdd8c3c083b..d2112c268fd1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2824,6 +2824,9 @@ context_switch(struct rq *rq, struct task_struct *prev,
prev->active_mm = NULL;
rq->prev_mm = oldmm;
}
+
+ rq->clock_skip_update = 0;
+
/*
* Since the runqueue lock will be released by the next
* task (which is an invalid locking op but in the case
@@ -3316,7 +3319,6 @@ static void __sched notrace __schedule(bool preempt)
next = pick_next_task(rq, prev, &rf);
clear_tsk_need_resched(prev);
clear_preempt_need_resched();
- rq->clock_skip_update = 0;

if (likely(prev != next)) {
rq->nr_switches++;
@@ -3326,6 +3328,7 @@ static void __sched notrace __schedule(bool preempt)
trace_sched_switch(preempt, prev, next);
rq = context_switch(rq, prev, next, &rf); /* unlocks the rq */
} else {
+ rq->clock_skip_update = 0;
rq_unpin_lock(rq, &rf);
raw_spin_unlock_irq(&rq->lock);
}
--
2.7.3