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Date: Tue, 3 Sep 2013 16:54:26 -0400
From: Tejun Heo <tj@...nel.org>
To: lizefan@...wei.com
Cc: containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v2 8/9] cgroup: implement for_each_css()
There are enough places where css's of a cgroup are iterated, which
currently uses for_each_root_subsys() + explicit cgroup_css(). This
patch implements for_each_css() and replaces the above combination
with it.
This patch doesn't introduce any behavior changes.
v2: Updated to apply cleanly on top of v2 of "cgroup: fix css leaks on
online_css() failure"
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Li Zefan <lizefan@...wei.com>
---
kernel/cgroup.c | 57 ++++++++++++++++++++++++++++++--------------------------
1 file changed, 31 insertions(+), 26 deletions(-)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -297,6 +297,21 @@ static int notify_on_release(const struc
}
/**
+ * for_each_css - iterate all css's of a cgroup
+ * @css: the iteration cursor
+ * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
+ * @cgrp: the target cgroup to iterate css's of
+ *
+ * Should be called under cgroup_mutex.
+ */
+#define for_each_css(css, ssid, cgrp) \
+ for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
+ if (!((css) = rcu_dereference_check( \
+ (cgrp)->subsys[(ssid)], \
+ lockdep_is_held(&cgroup_mutex)))) { } \
+ else
+
+/**
* for_each_subsys - iterate all loaded cgroup subsystems
* @ss: the iteration cursor
* @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
@@ -2013,8 +2028,8 @@ static int cgroup_attach_task(struct cgr
bool threadgroup)
{
int retval, i, group_size;
- struct cgroup_subsys *ss, *failed_ss = NULL;
struct cgroupfs_root *root = cgrp->root;
+ struct cgroup_subsys_state *css, *failed_css = NULL;
/* threadgroup list cursor and array */
struct task_struct *leader = tsk;
struct task_and_cgroup *tc;
@@ -2087,13 +2102,11 @@ static int cgroup_attach_task(struct cgr
/*
* step 1: check that we can legitimately attach to the cgroup.
*/
- for_each_root_subsys(root, ss) {
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
-
- if (ss->can_attach) {
- retval = ss->can_attach(css, &tset);
+ for_each_css(css, i, cgrp) {
+ if (css->ss->can_attach) {
+ retval = css->ss->can_attach(css, &tset);
if (retval) {
- failed_ss = ss;
+ failed_css = css;
goto out_cancel_attach;
}
}
@@ -2129,12 +2142,9 @@ static int cgroup_attach_task(struct cgr
/*
* step 4: do subsystem attach callbacks.
*/
- for_each_root_subsys(root, ss) {
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
-
- if (ss->attach)
- ss->attach(css, &tset);
- }
+ for_each_css(css, i, cgrp)
+ if (css->ss->attach)
+ css->ss->attach(css, &tset);
/*
* step 5: success! and cleanup
@@ -2151,13 +2161,11 @@ out_put_css_set_refs:
}
out_cancel_attach:
if (retval) {
- for_each_root_subsys(root, ss) {
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
-
- if (ss == failed_ss)
+ for_each_css(css, i, cgrp) {
+ if (css == failed_css)
break;
- if (ss->cancel_attach)
- ss->cancel_attach(css, &tset);
+ if (css->ss->cancel_attach)
+ css->ss->cancel_attach(css, &tset);
}
}
out_free_group_list:
@@ -4700,8 +4708,9 @@ static int cgroup_destroy_locked(struct
{
struct dentry *d = cgrp->dentry;
struct cgroup_event *event, *tmp;
- struct cgroup_subsys *ss;
+ struct cgroup_subsys_state *css;
bool empty;
+ int ssid;
lockdep_assert_held(&d->d_inode->i_mutex);
lockdep_assert_held(&cgroup_mutex);
@@ -4721,12 +4730,8 @@ static int cgroup_destroy_locked(struct
* will be invoked to perform the rest of destruction once the
* percpu refs of all css's are confirmed to be killed.
*/
- for_each_root_subsys(cgrp->root, ss) {
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
-
- if (css)
- kill_css(css);
- }
+ for_each_css(css, ssid, cgrp)
+ kill_css(css);
/*
* Mark @cgrp dead. This prevents further task migration and child
--
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