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authorTejun Heo <tj@kernel.org>2013-06-21 15:52:33 -0700
committerTejun Heo <tj@kernel.org>2013-06-26 10:48:48 -0700
commita4ea1cc90604df08d471ae84eb9627319d10c844 (patch)
tree73e12ef6845c5cf5bac0b8a2e4e6c4dd03af0a1b /kernel/cgroup.c
parenta8ad805cfde00be8fe3b3dae8890996dbeb91e2c (diff)
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>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c21
1 files changed, 12 insertions, 9 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ee9f0c1c8bf..4ed86773fff 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1427,7 +1427,7 @@ static void init_cgroup_root(struct cgroupfs_root *root)
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 @@ static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
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 @@ static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
/* 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 @@ int __init cgroup_init_early(void)
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 @@ bool css_is_ancestor(struct cgroup_subsys_state *child,
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 @@ static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
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 @@ static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
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);