From: Li Hua <hucool.lihua@huawei.com>
To: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
<linux-kernel@vger.kernel.org>, <hucool.lihua@huawei.com>,
<stable@vger.kernel.org>
Subject: [PATCH v2, RESEND] sched/rt: Try to restart rt period timer when rt runtime exceeded
Date: Fri, 3 Dec 2021 03:36:18 +0000 [thread overview]
Message-ID: <20211203033618.11895-1-hucool.lihua@huawei.com> (raw)
When rt_runtime is modified from -1 to a valid control value, it may
cause the task to be throttled all the time. Operations like the following
will trigger the bug. E.g:
1. echo -1 > /proc/sys/kernel/sched_rt_runtime_us
2. Run a FIFO task named A that executes while(1)
3. echo 950000 > /proc/sys/kernel/sched_rt_runtime_us
When rt_runtime is -1, The rt period timer will not be activated when task
A enqueued. And then the task will be throttled after setting rt_runtime to
950,000. The task will always be throttled because the rt period timer is
not activated.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Li Hua <hucool.lihua@huawei.com>
---
v1->v2:
- call do_start_rt_bandwidth to reduce repetitive code.
- use raw_spin_lock_irqsave to avoid deadlock on a timer context.
---
kernel/sched/rt.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index b48baaba2fc2..7b4f4fbbb404 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -52,11 +52,8 @@ void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
rt_b->rt_period_timer.function = sched_rt_period_timer;
}
-static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
+static inline void do_start_rt_bandwidth(struct rt_bandwidth *rt_b)
{
- if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
- return;
-
raw_spin_lock(&rt_b->rt_runtime_lock);
if (!rt_b->rt_period_active) {
rt_b->rt_period_active = 1;
@@ -75,6 +72,14 @@ static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
raw_spin_unlock(&rt_b->rt_runtime_lock);
}
+static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
+{
+ if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
+ return;
+
+ do_start_rt_bandwidth(rt_b);
+}
+
void init_rt_rq(struct rt_rq *rt_rq)
{
struct rt_prio_array *array;
@@ -1031,13 +1036,17 @@ static void update_curr_rt(struct rq *rq)
for_each_sched_rt_entity(rt_se) {
struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
+ int exceeded;
if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
raw_spin_lock(&rt_rq->rt_runtime_lock);
rt_rq->rt_time += delta_exec;
- if (sched_rt_runtime_exceeded(rt_rq))
+ exceeded = sched_rt_runtime_exceeded(rt_rq);
+ if (exceeded)
resched_curr(rq);
raw_spin_unlock(&rt_rq->rt_runtime_lock);
+ if (exceeded)
+ do_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
}
}
}
@@ -2911,8 +2920,12 @@ static int sched_rt_global_validate(void)
static void sched_rt_do_global(void)
{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
def_rt_bandwidth.rt_runtime = global_rt_runtime();
def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
+ raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
}
int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
--
2.17.1
next reply other threads:[~2021-12-03 3:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-03 3:36 Li Hua [this message]
2021-12-03 7:17 ` [PATCH v2, RESEND] sched/rt: Try to restart rt period timer when rt runtime exceeded Greg KH
2021-12-07 1:38 ` Lihua (lihua, ran)
2021-12-04 11:34 ` Peter Zijlstra
2021-12-06 1:42 ` Lihua (lihua, ran)
2021-12-07 14:22 ` [tip: sched/core] " tip-bot2 for Li Hua
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