linux-kernel - [PATCH v2 sched_ext/for-6.14-fixes 1/2] tools/sched_ext: Add helper to check task migration state

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Message-ID: <Z5Ub5Bp2BFCbuZwx@gpd3>
Date: Sat, 25 Jan 2025 18:14:12 +0100
From: Andrea Righi <arighi@...dia.com>
To: Tejun Heo <tj@...nel.org>, David Vernet <void@...ifault.com>,
	Changwoo Min <changwoo@...lia.com>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH v2 sched_ext/for-6.14-fixes 1/2] tools/sched_ext: Add helper
 to check task migration state

Introduce a new helper for BPF schedulers to determine whether a task
can migrate or not (supporting both SMP and UP systems).

Fixes: e9fe182772dc ("sched_ext: selftests/dsp_local_on: Fix sporadic failures")
Signed-off-by: Andrea Righi <arighi@...dia.com>
---
 tools/sched_ext/include/scx/common.bpf.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

ChangeLog v1 -> v2:
 - add missing inline

diff --git a/tools/sched_ext/include/scx/common.bpf.h b/tools/sched_ext/include/scx/common.bpf.h
index f3e15e9efa76..f254a39b86a5 100644
--- a/tools/sched_ext/include/scx/common.bpf.h
+++ b/tools/sched_ext/include/scx/common.bpf.h
@@ -404,6 +404,17 @@ static __always_inline const struct cpumask *cast_mask(struct bpf_cpumask *mask)
 	return (const struct cpumask *)mask;
 }
 
+/*
+ * Return true if task @p cannot migrate to a different CPU, false
+ * otherwise.
+ */
+static inline bool is_migration_disabled(const struct task_struct *p)
+{
+	if (bpf_core_field_exists(p->migration_disabled))
+		return p->migration_disabled;
+	return false;
+}
+
 /* rcu */
 void bpf_rcu_read_lock(void) __ksym;
 void bpf_rcu_read_unlock(void) __ksym;
-- 
2.48.1