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author | Tejun Heo <tj@kernel.org> | 2013-08-13 20:22:50 -0400 |
---|---|---|
committer | Tejun Heo <tj@kernel.org> | 2013-08-13 20:22:50 -0400 |
commit | f20104de55a212a9742d8df1807f1f29dc95b748 (patch) | |
tree | c7686dae4a73615ba67dc6fd4cfe9e7b89cf9708 /kernel | |
parent | 223dbc38d2a8745a93749dc75ed909e274ce075d (diff) | |
download | op-kernel-dev-f20104de55a212a9742d8df1807f1f29dc95b748.zip op-kernel-dev-f20104de55a212a9742d8df1807f1f29dc95b748.tar.gz |
cgroup: replace cgroup->css_kill_cnt with ->nr_css
Currently, css (cgroup_subsys_state) lifetime is tied to that of the
associated cgroup. With the planned unified hierarchy, css's will be
dynamically created and destroyed within the lifetime of a cgroup. To
enable such usages, css's will be individually RCU protected instead
of being tied to the cgroup.
cgroup->css_kill_cnt is used during cgroup destruction to wait for css
reference count disable; however, this model doesn't work once css's
lifetimes are managed separately from cgroup's. This patch replaces
it with cgroup->nr_css which is an cgroup_mutex protected integer
counting the number of attached css's. The count is incremented from
online_css() and decremented after refcnt kill is confirmed. If the
count reaches zero and the cgroup is marked dead, the second stage of
cgroup destruction is kicked off. If a cgroup doesn't have any css
attached at the time of rmdir, cgroup_destroy_locked() now invokes the
second stage directly as no css kill confirmation would happen.
cgroup_offline_fn() - the second step of cgroup destruction - is
renamed to cgroup_destroy_css_killed() and now expects to be called
with cgroup_mutex held.
While this patch changes how css destruction is punted to work items,
it shouldn't change any visible behavior.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/cgroup.c | 52 |
1 files changed, 28 insertions, 24 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 398ffbb..174f4c3 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -218,7 +218,7 @@ static int need_forkexit_callback __read_mostly; static struct cftype cgroup_base_files[]; -static void cgroup_offline_fn(struct work_struct *work); +static void cgroup_destroy_css_killed(struct cgroup *cgrp); static int cgroup_destroy_locked(struct cgroup *cgrp); static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], bool is_add); @@ -4335,6 +4335,7 @@ static int online_css(struct cgroup_subsys_state *css) ret = ss->css_online(css); if (!ret) { css->flags |= CSS_ONLINE; + css->cgroup->nr_css++; rcu_assign_pointer(css->cgroup->subsys[ss->subsys_id], css); } return ret; @@ -4545,16 +4546,6 @@ static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) return cgroup_create(c_parent, dentry, mode | S_IFDIR); } -static void cgroup_css_killed(struct cgroup *cgrp) -{ - if (!atomic_dec_and_test(&cgrp->css_kill_cnt)) - return; - - /* percpu ref's of all css's are killed, kick off the next step */ - INIT_WORK(&cgrp->destroy_work, cgroup_offline_fn); - schedule_work(&cgrp->destroy_work); -} - /* * This is called when the refcnt of a css is confirmed to be killed. * css_tryget() is now guaranteed to fail. @@ -4565,7 +4556,17 @@ static void css_killed_work_fn(struct work_struct *work) container_of(work, struct cgroup_subsys_state, destroy_work); struct cgroup *cgrp = css->cgroup; - cgroup_css_killed(cgrp); + mutex_lock(&cgroup_mutex); + + /* + * If @cgrp is marked dead, it's waiting for refs of all css's to + * be disabled before proceeding to the second phase of cgroup + * destruction. If we are the last one, kick it off. + */ + if (!--cgrp->nr_css && cgroup_is_dead(cgrp)) + cgroup_destroy_css_killed(cgrp); + + mutex_unlock(&cgroup_mutex); } /* css kill confirmation processing requires process context, bounce */ @@ -4634,11 +4635,10 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) * Use percpu_ref_kill_and_confirm() to get notifications as each * css is confirmed to be seen as killed on all CPUs. The * notification callback keeps track of the number of css's to be - * killed and schedules cgroup_offline_fn() to perform the rest of - * destruction once the percpu refs of all css's are confirmed to - * be killed. + * killed and invokes cgroup_destroy_css_killed() to perform the + * rest of destruction once the percpu refs of all css's are + * confirmed to be killed. */ - atomic_set(&cgrp->css_kill_cnt, 1); for_each_root_subsys(cgrp->root, ss) { struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id); @@ -4648,10 +4648,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) */ percpu_ref_get(&css->refcnt); - atomic_inc(&cgrp->css_kill_cnt); percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn); } - cgroup_css_killed(cgrp); /* * Mark @cgrp dead. This prevents further task migration and child @@ -4669,6 +4667,15 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) raw_spin_unlock(&release_list_lock); /* + * If @cgrp has css's attached, the second stage of cgroup + * destruction is kicked off from css_killed_work_fn() after the + * refs of all attached css's are killed. If @cgrp doesn't have + * any css, we kick it off here. + */ + if (!cgrp->nr_css) + cgroup_destroy_css_killed(cgrp); + + /* * Clear and remove @cgrp directory. The removal puts the base ref * but we aren't quite done with @cgrp yet, so hold onto it. */ @@ -4693,7 +4700,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) }; /** - * cgroup_offline_fn - the second step of cgroup destruction + * cgroup_destroy_css_killed - the second step of cgroup destruction * @work: cgroup->destroy_free_work * * This function is invoked from a work item for a cgroup which is being @@ -4702,14 +4709,13 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) * is the second step of destruction described in the comment above * cgroup_destroy_locked(). */ -static void cgroup_offline_fn(struct work_struct *work) +static void cgroup_destroy_css_killed(struct cgroup *cgrp) { - struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work); struct cgroup *parent = cgrp->parent; struct dentry *d = cgrp->dentry; struct cgroup_subsys *ss; - mutex_lock(&cgroup_mutex); + lockdep_assert_held(&cgroup_mutex); /* * css_tryget() is guaranteed to fail now. Tell subsystems to @@ -4743,8 +4749,6 @@ static void cgroup_offline_fn(struct work_struct *work) set_bit(CGRP_RELEASABLE, &parent->flags); check_for_release(parent); - - mutex_unlock(&cgroup_mutex); } static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry) |