[PATCH v3 09/14] cgroup/cpuset: Remove redundant rcu_read_lock/unlock() in spin_lock

[pengdonglin]

From: pengdonglin <pengdong...@xiaomi.com>

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 <long...@redhat.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Acked-by: Waiman Long <long...@redhat.com>
Signed-off-by: pengdonglin <pengdong...@xiaomi.com>
Signed-off-by: pengdonglin <dolinux.p...@gmail.com>
---
 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