Commit 440989c1 authored Jun 27, 2025 by Juri Lelli Committed by Peter Zijlstra Jul 14, 2025

sched/deadline: Fix accounting after global limits change



A global limits change (sched_rt_handler() logic) currently leaves stale
and/or incorrect values in variables related to accounting (e.g.
extra_bw).

Properly clean up per runqueue variables before implementing the change
and rebuild scheduling domains (so that accounting is also properly
restored) after such a change is complete.

Reported-by: Marcel Ziswiler <marcel.ziswiler@codethink.co.uk>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Marcel Ziswiler <marcel.ziswiler@codethink.co.uk> # nuc & rock5b
Link: https://lore.kernel.org/r/20250627115118.438797-4-juri.lelli@redhat.com

parent fcc9276c

kernel/sched/deadline.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -3183,6 +3183,9 @@ void sched_dl_do_global(void)
		if (global_rt_runtime() != RUNTIME_INF)
		new_bw = to_ratio(global_rt_period(), global_rt_runtime());

		for_each_possible_cpu(cpu)
		init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);

		for_each_possible_cpu(cpu) {
		rcu_read_lock_sched();

		@@ -3198,7 +3201,6 @@ void sched_dl_do_global(void)
		raw_spin_unlock_irqrestore(&dl_b->lock, flags);

		rcu_read_unlock_sched();
		init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);
		}
		}

kernel/sched/rt.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -2886,6 +2886,12 @@ static int sched_rt_handler(const struct ctl_table table, int write, void buff
		sched_domains_mutex_unlock();
		mutex_unlock(&mutex);

		/*
		* After changing maximum available bandwidth for DEADLINE, we need to
		* recompute per root domain and per cpus variables accordingly.
		*/
		rebuild_sched_domains();

		return ret;
		}