From: Li Hua hucool.lihua@huawei.com
[ Upstream commit 9b58e976b3b391c0cf02e038d53dd0478ed3013c ]
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.
Fixes: d0b27fa77854 ("sched: rt-group: synchonised bandwidth period") Reported-by: Hulk Robot hulkci@huawei.com Signed-off-by: Li Hua hucool.lihua@huawei.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/20211203033618.11895-1-hucool.lihua@huawei.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 b980cc96604fa..70e8cd3954745 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -50,11 +50,8 @@ 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; @@ -72,6 +69,14 @@ 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; @@ -980,13 +985,17 @@ 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)); } } } @@ -2655,8 +2664,12 @@ 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,