sched/deadline: Fix accounting after global limits change

[ Upstream commit 440989c10f4e32620e9e2717ca52c3ed7ae11048 ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 0a47e5155897cd1b0b04a58624f10dad2411f7e5..53e3670fbb1e05409cb5aab49a12b6b2643362fb 100644 (file)
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -3227,6 +3227,9 @@ 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();
 
@@ -3242,7 +3245,6 @@ 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);
        }
 }
 

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 172c588de54270be8a402908dc6343681a91ded7..6ad6717084ed8f9b3edd01bf2ba37933a3a4d31c 100644 (file)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2951,6 +2951,12 @@ undo:
        }
        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;
 }