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@xxxxxxxxxx>
Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
---
kernel/cgroup.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1416,7 +1416,7 @@ static void init_cgroup_root(struct cgro
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);
}
@@ -2535,7 +2535,7 @@ static int cgroup_rename(struct inode *o
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);
@@ -4154,13 +4154,15 @@ static int cgroup_populate_dir(struct cg
/* This cgroup is ready now */
for_each_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;
@@ -4837,7 +4839,7 @@ int __init cgroup_init_early(void)
css_set_count = 1;
init_cgroup_root(&rootnode);
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 = dummytop;
@@ -5371,7 +5373,8 @@ bool css_is_ancestor(struct cgroup_subsy
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;
@@ -5437,8 +5440,8 @@ static int __init_or_module cgroup_init_
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;
}
@@ -5452,7 +5455,7 @@ static int alloc_css_id(struct cgroup_su
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);
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