[PATCH] sched/rt: silence double clock update warning by using rq_lock wrappers

Phil Auld
2019-08-15T14:53:58Z

With WARN_DOUBLE_CLOCK enabled a false positive warning can occur in rt

[] rq->clock_update_flags & RQCF_UPDATED
[] WARNING: CPU: 6 PID: 21426 at kernel/sched/core.c:225
update_rq_clock+0x90/0x130
[] Call Trace:
[] update_rq_clock+0x90/0x130
[] sched_rt_period_timer+0x11f/0x340
[] __hrtimer_run_queues+0x100/0x280
[] hrtimer_interrupt+0x100/0x220
[] smp_apic_timer_interrupt+0x6a/0x130
[] apic_timer_interrupt+0xf/0x20

sched_rt_period_timer does:
raw_spin_lock(&rq->lock);
update_rq_clock(rq);

which triggers the warning because of not using the rq_lock wrappers.
So, use the wrappers.

Signed-off-by: Phil Auld <pauld@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
kernel/sched/rt.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index a532558a5176..0846e71114ee 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -831,6 +831,7 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
int enqueue = 0;
struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
struct rq *rq = rq_of_rt_rq(rt_rq);
+ struct rq_flags rf;
int skip;

/*
@@ -845,7 +846,7 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
if (skip)
continue;

- raw_spin_lock(&rq->lock);
+ rq_lock(rq, &rf);
update_rq_clock(rq);

if (rt_rq->rt_time) {
@@ -883,7 +884,7 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)

if (enqueue)
sched_rt_rq_enqueue(rt_rq);
- raw_spin_unlock(&rq->lock);
+ rq_unlock(rq, &rf);
}

if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
--
2.18.0