From: pengdonglin 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: Tejun Heo Cc: Johannes Weiner Cc: Waiman Long Signed-off-by: pengdonglin Signed-off-by: pengdonglin --- kernel/cgroup/cgroup.c | 2 -- kernel/cgroup/debug.c | 4 ---- 2 files changed, 6 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 312c6a8b55bb..db9e00a559df 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -2944,14 +2944,12 @@ int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader, /* look up all src csets */ spin_lock_irq(&css_set_lock); - rcu_read_lock(); task = leader; do { cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx); if (!threadgroup) break; } while_each_thread(leader, task); - rcu_read_unlock(); spin_unlock_irq(&css_set_lock); /* prepare dst csets and commit */ diff --git a/kernel/cgroup/debug.c b/kernel/cgroup/debug.c index 80aa3f027ac3..81ea38dd6f9d 100644 --- a/kernel/cgroup/debug.c +++ b/kernel/cgroup/debug.c @@ -49,7 +49,6 @@ static int current_css_set_read(struct seq_file *seq, void *v) return -ENODEV; spin_lock_irq(&css_set_lock); - rcu_read_lock(); cset = task_css_set(current); refcnt = refcount_read(&cset->refcount); seq_printf(seq, "css_set %pK %d", cset, refcnt); @@ -67,7 +66,6 @@ static int current_css_set_read(struct seq_file *seq, void *v) seq_printf(seq, "%2d: %-4s\t- %p[%d]\n", ss->id, ss->name, css, css->id); } - rcu_read_unlock(); spin_unlock_irq(&css_set_lock); cgroup_kn_unlock(of->kn); return 0; @@ -95,7 +93,6 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v) return -ENOMEM; spin_lock_irq(&css_set_lock); - rcu_read_lock(); cset = task_css_set(current); list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { struct cgroup *c = link->cgrp; @@ -104,7 +101,6 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v) seq_printf(seq, "Root %d group %s\n", c->root->hierarchy_id, name_buf); } - rcu_read_unlock(); spin_unlock_irq(&css_set_lock); kfree(name_buf); return 0; -- 2.34.1