[PATCH 6.6 005/283] rcu: s/boost_kthread_mutex/kthread_mutex

Sasha Levin
2026-02-28T18:07:14Z

From: Frederic Weisbecker <frederic@kernel.org>

[ Upstream commit 7836b270607676ed1c0c6a4a840a2ede9437a6a1 ]

This mutex is currently protecting per node boost kthreads creation and
affinity setting across CPU hotplug operations.

Since the expedited kworkers will soon be split per node as well, they
will be subject to the same concurrency constraints against hotplug.

Therefore their creation and affinity tuning operations will be grouped
with those of boost kthreads and then rely on the same mutex.

To prepare for that, generalize its name.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Stable-dep-of: d41e37f26b31 ("rcu: Fix rcu_read_unlock() deadloop due to softirq")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/rcu/tree.c | 2 +-
kernel/rcu/tree.h | 2 +-
kernel/rcu/tree_plugin.h | 10 +++++-----
3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 607b2e68fa4c2..43133dff2a04b 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4874,7 +4874,7 @@ static void __init rcu_init_one(void)
init_waitqueue_head(&rnp->exp_wq[2]);
init_waitqueue_head(&rnp->exp_wq[3]);
spin_lock_init(&rnp->exp_lock);
- mutex_init(&rnp->boost_kthread_mutex);
+ mutex_init(&rnp->kthread_mutex);
raw_spin_lock_init(&rnp->exp_poll_lock);
rnp->exp_seq_poll_rq = RCU_GET_STATE_COMPLETED;
INIT_WORK(&rnp->exp_poll_wq, sync_rcu_do_polled_gp);
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 71403d22a8465..f8408e7a5f824 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -113,7 +113,7 @@ struct rcu_node {
/* side effect, not as a lock. */
unsigned long boost_time;
/* When to start boosting (jiffies). */
- struct mutex boost_kthread_mutex;
+ struct mutex kthread_mutex;
/* Exclusion for thread spawning and affinity */
/* manipulation. */
struct task_struct *boost_kthread_task;
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 8707f155afb6d..f178a8bb83650 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1229,7 +1229,7 @@ static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
struct sched_param sp;
struct task_struct *t;

- mutex_lock(&rnp->boost_kthread_mutex);
+ mutex_lock(&rnp->kthread_mutex);
if (rnp->boost_kthread_task || !rcu_scheduler_fully_active)
goto out;

@@ -1246,7 +1246,7 @@ static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */

out:
- mutex_unlock(&rnp->boost_kthread_mutex);
+ mutex_unlock(&rnp->kthread_mutex);
}

/*
@@ -1258,7 +1258,7 @@ static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
* no outgoing CPU. If there are no CPUs left in the affinity set,
* this function allows the kthread to execute on any CPU.
*
- * Any future concurrent calls are serialized via ->boost_kthread_mutex.
+ * Any future concurrent calls are serialized via ->kthread_mutex.
*/
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
{
@@ -1271,7 +1271,7 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
return;
if (!zalloc_cpumask_var(&cm, GFP_KERNEL))
return;
- mutex_lock(&rnp->boost_kthread_mutex);
+ mutex_lock(&rnp->kthread_mutex);
mask = rcu_rnp_online_cpus(rnp);
for_each_leaf_node_possible_cpu(rnp, cpu)
if ((mask & leaf_node_cpu_bit(rnp, cpu)) &&
@@ -1284,7 +1284,7 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
cpumask_clear_cpu(outgoingcpu, cm);
}
set_cpus_allowed_ptr(t, cm);
- mutex_unlock(&rnp->boost_kthread_mutex);
+ mutex_unlock(&rnp->kthread_mutex);
free_cpumask_var(cm);
}

--
2.51.0