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authorTejun Heo <tj@kernel.org>2014-06-28 08:10:14 -0400
committerTejun Heo <tj@kernel.org>2014-06-28 08:10:14 -0400
commit9a1049da9bd2cd83fe11d46433e603c193aa9c71 (patch)
tree007d2843abf0f064c294659334e69e297ffc2b74 /kernel/cgroup.c
parent7d742075120deb831c7b94c268ca20d409e91d60 (diff)
downloadlwn-9a1049da9bd2cd83fe11d46433e603c193aa9c71.tar.gz
lwn-9a1049da9bd2cd83fe11d46433e603c193aa9c71.zip
percpu-refcount: require percpu_ref to be exited explicitly
Currently, a percpu_ref undoes percpu_ref_init() automatically by freeing the allocated percpu area when the percpu_ref is killed. While seemingly convenient, this has the following niggles. * It's impossible to re-init a released reference counter without going through re-allocation. * In the similar vein, it's impossible to initialize a percpu_ref count with static percpu variables. * We need and have an explicit destructor anyway for failure paths - percpu_ref_cancel_init(). This patch removes the automatic percpu counter freeing in percpu_ref_kill_rcu() and repurposes percpu_ref_cancel_init() into a generic destructor now named percpu_ref_exit(). percpu_ref_destroy() is considered but it gets confusing with percpu_ref_kill() while "exit" clearly indicates that it's the counterpart of percpu_ref_init(). All percpu_ref_cancel_init() users are updated to invoke percpu_ref_exit() instead and explicit percpu_ref_exit() calls are added to the destruction path of all percpu_ref users. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Benjamin LaHaise <bcrl@kvack.org> Cc: Kent Overstreet <kmo@daterainc.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Benjamin LaHaise <bcrl@kvack.org> Cc: Nicholas A. Bellinger <nab@linux-iscsi.org> Cc: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7868fc3c0bc5..c06aa5e257a8 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1638,7 +1638,7 @@ destroy_root:
exit_root_id:
cgroup_exit_root_id(root);
cancel_ref:
- percpu_ref_cancel_init(&root_cgrp->self.refcnt);
+ percpu_ref_exit(&root_cgrp->self.refcnt);
out:
free_cgrp_cset_links(&tmp_links);
return ret;
@@ -4133,6 +4133,8 @@ static void css_free_work_fn(struct work_struct *work)
container_of(work, struct cgroup_subsys_state, destroy_work);
struct cgroup *cgrp = css->cgroup;
+ percpu_ref_exit(&css->refcnt);
+
if (css->ss) {
/* css free path */
if (css->parent)
@@ -4330,7 +4332,7 @@ err_list_del:
err_free_id:
cgroup_idr_remove(&ss->css_idr, css->id);
err_free_percpu_ref:
- percpu_ref_cancel_init(&css->refcnt);
+ percpu_ref_exit(&css->refcnt);
err_free_css:
call_rcu(&css->rcu_head, css_free_rcu_fn);
return err;
@@ -4441,7 +4443,7 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
out_free_id:
cgroup_idr_remove(&root->cgroup_idr, cgrp->id);
out_cancel_ref:
- percpu_ref_cancel_init(&cgrp->self.refcnt);
+ percpu_ref_exit(&cgrp->self.refcnt);
out_free_cgrp:
kfree(cgrp);
out_unlock: