sched/deadline: Clear dl_entity params when setscheduling to different class (a5e7be3b) · Commits · 戴 / test

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.alessandrelli@gmail.com> Reported-by:

Daniel Wagner <daniel.wagner@bmw-carit.de> Reported-by:

Vincent Legout <vincent@legout.info> Tested-by:

Luca Abeni <luca.abeni@unitn.it> Tested-by:

Daniel Wagner <daniel.wagner@bmw-carit.de> Tested-by:

Vincent Legout <vincent@legout.info> Signed-off-by:

Juri Lelli <juri.lelli@arm.com> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Fabio Checconi <fchecconi@gmail.com> Cc: Dario Faggioli <raistlin@linux.it> Cc: Michael Trimarchi <michael@amarulasolutions.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1411118561-26323-2-git-send-email-juri.lelli@arm.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/sched/core.c

+15 −4

Original line number	Diff line number	Diff line
		@@ -1808,6 +1808,20 @@ int wake_up_state(struct task_struct *p, unsigned int state)
		return try_to_wake_up(p, state, 0);
		}

		/*
		* 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.
		@@ -1832,10 +1846,7 @@ 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);

kernel/sched/deadline.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1565,6 +1565,8 @@ 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,

kernel/sched/sched.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -130,6 +130,9 @@ 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:

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