From a7e546354d9c534dc045ce0cf9ff05d81351a751 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <frederic@kernel.org>
Date: Tue, 27 May 2025 15:35:14 +0200
Subject: cpuset: Provide lockdep check for cpuset lock held
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cpuset modifies partitions, including isolated, while holding the cpuset
mutex.

This means that holding the cpuset mutex is safe to synchronize against
housekeeping cpumask changes.

Provide a lockdep check to validate that.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: "Michal Koutný" <mkoutny@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Marco Crivellari <marco.crivellari@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Waiman Long <longman@redhat.com>
Cc: cgroups@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 kernel/cgroup/cpuset.c | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'kernel')

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 3afa72f8d579..5e2e3514c22e 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -283,6 +283,13 @@ void cpuset_full_unlock(void)
 	cpus_read_unlock();
 }
 
+#ifdef CONFIG_LOCKDEP
+bool lockdep_is_cpuset_held(void)
+{
+	return lockdep_is_held(&cpuset_mutex);
+}
+#endif
+
 static DEFINE_SPINLOCK(callback_lock);
 
 void cpuset_callback_lock_irq(void)
-- 
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