[PATCH v3 09/14] cgroup/cpuset: Remove redundant rcu_read_lock/unlock() in spin_lock
From: pengdonglin <hidden>
Date: 2025-09-16 04:49:14
Also in:
cgroups, intel-gfx, linux-acpi, linux-fsdevel, linux-nfs, linux-rt-devel, linux-s390, linux-security-module, linux-wireless, lkml
Subsystem:
control group (cgroup), control group - cpuset, the rest · Maintainers:
Tejun Heo, Johannes Weiner, Michal Koutný, Waiman Long, Linus Torvalds
From: pengdonglin <redacted>
Since commit a8bb74acd8efe ("rcu: Consolidate RCU-sched update-side function definitions")
there is no difference between rcu_read_lock(), rcu_read_lock_bh() and
rcu_read_lock_sched() in terms of RCU read section and the relevant grace
period. That means that spin_lock(), which implies rcu_read_lock_sched(),
also implies rcu_read_lock().
There is no need no explicitly start a RCU read section if one has already
been started implicitly by spin_lock().
Simplify the code and remove the inner rcu_read_lock() invocation.
Cc: Waiman Long <longman@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: pengdonglin <redacted>
Signed-off-by: pengdonglin <redacted>
---
kernel/cgroup/cpuset.c | 6 ------
1 file changed, 6 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 27adb04df675..9b7e8e8e9411 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c@@ -4073,7 +4073,6 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) struct cpuset *cs; spin_lock_irqsave(&callback_lock, flags); - rcu_read_lock(); cs = task_cs(tsk); if (cs != &top_cpuset)
@@ -4095,7 +4094,6 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) cpumask_copy(pmask, possible_mask); } - rcu_read_unlock(); spin_unlock_irqrestore(&callback_lock, flags); }
@@ -4168,9 +4166,7 @@ nodemask_t cpuset_mems_allowed(struct task_struct *tsk) unsigned long flags; spin_lock_irqsave(&callback_lock, flags); - rcu_read_lock(); guarantee_online_mems(task_cs(tsk), &mask); - rcu_read_unlock(); spin_unlock_irqrestore(&callback_lock, flags); return mask;
@@ -4265,10 +4261,8 @@ bool cpuset_current_node_allowed(int node, gfp_t gfp_mask) /* Not hardwall and node outside mems_allowed: scan up cpusets */ spin_lock_irqsave(&callback_lock, flags); - rcu_read_lock(); cs = nearest_hardwall_ancestor(task_cs(current)); allowed = node_isset(node, cs->mems_allowed); - rcu_read_unlock(); spin_unlock_irqrestore(&callback_lock, flags); return allowed;
--
2.34.1