When a task is using SCHED_DEADLINE and the user setschedules it to a different
class its sched_dl_entity static parameters are not cleaned up. This causes a
bug if the user sets it back to SCHED_DEADLINE with the same parameters again.
The problem resides in the check we perform at the very beginning of
dl_overflow():
if (new_bw == p->dl.dl_bw)
return 0;
This condition is met in the case depicted above, so the function returns and
dl_b->total_bw is not updated (the p->dl.dl_bw is not added to it). After this,
admission control is broken.
This patch fixes the thing, properly clearing static parameters for a task
that ceases to use SCHED_DEADLINE.
Reported-by: Daniele Alessandrelli <[email protected]>
Reported-by: Daniel Wagner <[email protected]>
Reported-by: Vincent Legout <[email protected]>
Tested-by: Luca Abeni <[email protected]>
Signed-off-by: Juri Lelli <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Dario Faggioli <[email protected]>
Cc: Michael Trimarchi <[email protected]>
Cc: Fabio Checconi <[email protected]>
Cc: [email protected]
---
kernel/sched/core.c | 19 +++++++++++++++----
kernel/sched/deadline.c | 2 ++
kernel/sched/sched.h | 3 +++
3 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ec1a286..581a429 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1776,6 +1776,20 @@ int wake_up_state(struct task_struct *p, unsigned int
state)
}
/*
+ * This function clears the sched_dl_entity static params.
+ */
+void __dl_clear_params(struct task_struct *p)
+{
+ struct sched_dl_entity *dl_se = &p->dl;
+
+ dl_se->dl_runtime = 0;
+ dl_se->dl_deadline = 0;
+ dl_se->dl_period = 0;
+ dl_se->flags = 0;
+ dl_se->dl_bw = 0;
+}
+
+/*
* Perform scheduler related setup for a newly forked process p.
* p is forked by current.
*
@@ -1799,10 +1813,7 @@ static void __sched_fork(unsigned long clone_flags,
struct task_struct *p)
RB_CLEAR_NODE(&p->dl.rb_node);
hrtimer_init(&p->dl.dl_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- p->dl.dl_runtime = p->dl.runtime = 0;
- p->dl.dl_deadline = p->dl.deadline = 0;
- p->dl.dl_period = 0;
- p->dl.flags = 0;
+ __dl_clear_params(p);
INIT_LIST_HEAD(&p->rt.run_list);
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 255ce13..4a51b14 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1569,6 +1569,8 @@ static void switched_from_dl(struct rq *rq, struct
task_struct *p)
if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy))
hrtimer_try_to_cancel(&p->dl.dl_timer);
+ __dl_clear_params(p);
+
#ifdef CONFIG_SMP
/*
* Since this might be the only -deadline task on the rq,
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 579712f..4890484 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -126,6 +126,9 @@ struct rt_bandwidth {
u64 rt_runtime;
struct hrtimer rt_period_timer;
};
+
+void __dl_clear_params(struct task_struct *p);
+
/*
* To keep the bandwidth of -deadline tasks and groups under control
* we need some place where:
--
2.1.0
--
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