diff options
| author | Tejun Heo <tj@kernel.org> | 2014-06-28 08:10:14 -0400 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2014-06-28 08:10:14 -0400 |
| commit | 9a1049da9bd2cd83fe11d46433e603c193aa9c71 (patch) | |
| tree | 007d2843abf0f064c294659334e69e297ffc2b74 /kernel/cgroup.c | |
| parent | 7d742075120deb831c7b94c268ca20d409e91d60 (diff) | |
| download | lwn-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.c | 8 |
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: |