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 <daniele.alessandre...@gmail.com> Reported-by: Daniel Wagner <daniel.wag...@bmw-carit.de> Reported-by: Vincent Legout <vinc...@legout.info> Tested-by: Luca Abeni <luca.ab...@unitn.it> Signed-off-by: Juri Lelli <juri.le...@arm.com> Cc: Ingo Molnar <mi...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Juri Lelli <juri.le...@gmail.com> Cc: Dario Faggioli <raist...@linux.it> Cc: Michael Trimarchi <mich...@amarulasolutions.com> Cc: Fabio Checconi <fchecc...@gmail.com> Cc: linux-kernel@vger.kernel.org --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/