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Message-ID: <20250702232944.3221001-6-joelagnelf@nvidia.com>
Date: Wed, 2 Jul 2025 19:29:30 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>,
Mel Gorman <mgorman@...e.de>,
Valentin Schneider <vschneid@...hat.com>
Cc: Joel Fernandes <joelagnelf@...dia.com>,
Tejun Heo <tj@...nel.org>,
David Vernet <void@...ifault.com>,
Andrea Righi <arighi@...dia.com>,
Changwoo Min <changwoo@...lia.com>
Subject: [PATCH v6 05/14] sched/deadline: Return EBUSY if dl_bw_cpus is zero
Hotplugged CPUs coming online do an enqueue but are not a part of any
root domain containing cpu_active() CPUs. So in this case, don't mess
with accounting and we can retry later. Without this patch, we see
crashes with sched_ext selftest's hotplug test due to divide by zero.
Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>
---
kernel/sched/deadline.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 7129b61d548b..0e73577257ad 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1725,7 +1725,12 @@ int dl_server_apply_params(struct sched_dl_entity *dl_se, u64 runtime, u64 perio
cpus = dl_bw_cpus(cpu);
cap = dl_bw_capacity(cpu);
- if (__dl_overflow(dl_b, cap, old_bw, new_bw))
+ /*
+ * Hotplugged CPUs coming online do an enqueue but are not a part of any
+ * root domain containing cpu_active() CPUs. So in this case, don't mess
+ * with accounting and we can retry later.
+ */
+ if (!cpus || __dl_overflow(dl_b, cap, old_bw, new_bw))
return -EBUSY;
if (init) {
--
2.34.1
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