linux-kernel - [PATCH v6 05/14] sched/deadline: Return EBUSY if dl_bw

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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