cgroup: always use RCU accessors for protected accesses
kernel/cgroup.c still has places where a RCU pointer is set and
accessed directly without going through RCU_INIT_POINTER() or
rcu_dereference_protected(). They're all properly protected accesses
so nothing is broken but it leads to spurious sparse RCU address space
warnings.
Substitute direct accesses with RCU_INIT_POINTER() and
rcu_dereference_protected(). Note that %true is specified as the
extra condition for all derference updates. This isn't ideal as all
it does is suppressing warning without actually policing
synchronization rules; however, most are scheduled to be removed
pretty soon along with css_id itself, so no reason to be more
elaborate.
Combined with the previous changes, this removes all RCU related
sparse warnings from cgroup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by; Li Zefan <lizefan@huawei.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ee9f0c1..4ed8677 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1427,7 +1427,7 @@
INIT_LIST_HEAD(&root->root_list);
root->number_of_cgroups = 1;
cgrp->root = root;
- cgrp->name = &root_cgroup_name;
+ RCU_INIT_POINTER(cgrp->name, &root_cgroup_name);
init_cgroup_housekeeping(cgrp);
}
@@ -2558,7 +2558,7 @@
return ret;
}
- old_name = cgrp->name;
+ old_name = rcu_dereference_protected(cgrp->name, true);
rcu_assign_pointer(cgrp->name, name);
kfree_rcu(old_name, rcu_head);
@@ -4177,13 +4177,15 @@
/* This cgroup is ready now */
for_each_root_subsys(cgrp->root, ss) {
struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+ struct css_id *id = rcu_dereference_protected(css->id, true);
+
/*
* Update id->css pointer and make this css visible from
* CSS ID functions. This pointer will be dereferened
* from RCU-read-side without locks.
*/
- if (css->id)
- rcu_assign_pointer(css->id->css, css);
+ if (id)
+ rcu_assign_pointer(id->css, css);
}
return 0;
@@ -4863,7 +4865,7 @@
css_set_count = 1;
init_cgroup_root(&cgroup_dummy_root);
cgroup_root_count = 1;
- init_task.cgroups = &init_css_set;
+ RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
init_cgrp_cset_link.cset = &init_css_set;
init_cgrp_cset_link.cgrp = cgroup_dummy_top;
@@ -5380,7 +5382,8 @@
void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
{
- struct css_id *id = css->id;
+ struct css_id *id = rcu_dereference_protected(css->id, true);
+
/* When this is called before css_id initialization, id can be NULL */
if (!id)
return;
@@ -5446,8 +5449,8 @@
return PTR_ERR(newid);
newid->stack[0] = newid->id;
- newid->css = rootcss;
- rootcss->id = newid;
+ RCU_INIT_POINTER(newid->css, rootcss);
+ RCU_INIT_POINTER(rootcss->id, newid);
return 0;
}
@@ -5461,7 +5464,7 @@
subsys_id = ss->subsys_id;
parent_css = parent->subsys[subsys_id];
child_css = child->subsys[subsys_id];
- parent_id = parent_css->id;
+ parent_id = rcu_dereference_protected(parent_css->id, true);
depth = parent_id->depth + 1;
child_id = get_new_cssid(ss, depth);