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Message-ID: <20250904055716.87268-1-arighi@nvidia.com>
Date: Thu, 4 Sep 2025 07:57:16 +0200
From: Andrea Righi <arighi@...dia.com>
To: Tejun Heo <tj@...nel.org>,
David Vernet <void@...ifault.com>,
Changwoo Min <changwoo@...lia.com>
Cc: sched-ext@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: [PATCH sched_ext/for-6.18] sched_ext: Exit early on hotplug events during attach
There is no need to complete the entire scx initialization if a
scheduler is failing to be attached due to a hotplug event.
Exit early to avoid unnecessary work and simplify the attach flow.
Signed-off-by: Andrea Righi <arighi@...dia.com>
---
kernel/sched/ext.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 9ddf7a145db6b..489462290142a 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4445,7 +4445,7 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops)
return ERR_PTR(ret);
}
-static void check_hotplug_seq(struct scx_sched *sch,
+static int check_hotplug_seq(struct scx_sched *sch,
const struct sched_ext_ops *ops)
{
unsigned long long global_hotplug_seq;
@@ -4462,8 +4462,11 @@ static void check_hotplug_seq(struct scx_sched *sch,
SCX_ECODE_ACT_RESTART | SCX_ECODE_RSN_HOTPLUG,
"expected hotplug seq %llu did not match actual %llu",
ops->hotplug_seq, global_hotplug_seq);
+ return -EBUSY;
}
}
+
+ return 0;
}
static int validate_ops(struct scx_sched *sch, const struct sched_ext_ops *ops)
@@ -4560,7 +4563,11 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
if (((void (**)(void))ops)[i])
set_bit(i, sch->has_op);
- check_hotplug_seq(sch, ops);
+ ret = check_hotplug_seq(sch, ops);
+ if (ret) {
+ cpus_read_unlock();
+ goto err_disable;
+ }
scx_idle_update_selcpu_topology(ops);
cpus_read_unlock();
--
2.51.0
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