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authorTejun Heo <tj@kernel.org>2013-08-26 18:40:56 -0400
committerTejun Heo <tj@kernel.org>2013-08-26 18:40:56 -0400
commit7941cb027dccedec3c047271554ddcf4be2e0697 (patch)
tree72bf50000b99403d9610ac9d32d21900e06c1bc6 /kernel/cgroup.c
parent9fa4db334c7d9570aec7a5121e84fae99aae1d04 (diff)
downloadop-kernel-dev-7941cb027dccedec3c047271554ddcf4be2e0697.zip
op-kernel-dev-7941cb027dccedec3c047271554ddcf4be2e0697.tar.gz
cgroup: make cgroup_event hold onto cgroup_subsys_state instead of cgroup
Currently, each registered cgroup_event holds an extra reference to the cgroup. This is a bit weird as events are subsystem specific and will also be incorrect in the planned unified hierarchy as css (cgroup_subsys_state) may come and go dynamically across the lifetime of a cgroup. Holding onto cgroup won't prevent the target css from going away. Update cgroup_event to hold onto the css the traget file belongs to instead of cgroup. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c26
1 files changed, 12 insertions, 14 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a41dc87..12237a2 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3969,7 +3969,6 @@ static void cgroup_event_remove(struct work_struct *work)
struct cgroup_event *event = container_of(work, struct cgroup_event,
remove);
struct cgroup_subsys_state *css = event->css;
- struct cgroup *cgrp = css->cgroup;
remove_wait_queue(event->wqh, &event->wait);
@@ -3980,7 +3979,7 @@ static void cgroup_event_remove(struct work_struct *work)
eventfd_ctx_put(event->eventfd);
kfree(event);
- cgroup_dput(cgrp);
+ css_put(css);
}
/*
@@ -4103,12 +4102,16 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *dummy_css,
goto out_put_cfile;
}
- /* determine the css of @cfile and associate @event with it */
+ /*
+ * Determine the css of @cfile and associate @event with it.
+ * Remaining events are automatically removed on cgroup destruction
+ * but the removal is asynchronous, so take an extra ref.
+ */
rcu_read_lock();
ret = -EINVAL;
event->css = cgroup_css(cgrp, event->cft->ss);
- if (event->css)
+ if (event->css && css_tryget(event->css))
ret = 0;
rcu_read_unlock();
@@ -4122,28 +4125,21 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *dummy_css,
cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent);
if (cgrp_cfile != cgrp) {
ret = -EINVAL;
- goto out_put_cfile;
+ goto out_put_css;
}
if (!event->cft->register_event || !event->cft->unregister_event) {
ret = -EINVAL;
- goto out_put_cfile;
+ goto out_put_css;
}
ret = event->cft->register_event(event->css, event->cft,
event->eventfd, buffer);
if (ret)
- goto out_put_cfile;
+ goto out_put_css;
efile->f_op->poll(efile, &event->pt);
- /*
- * Events should be removed after rmdir of cgroup directory, but before
- * destroying subsystem state objects. Let's take reference to cgroup
- * directory dentry to do that.
- */
- dget(cgrp->dentry);
-
spin_lock(&cgrp->event_list_lock);
list_add(&event->list, &cgrp->event_list);
spin_unlock(&cgrp->event_list_lock);
@@ -4153,6 +4149,8 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *dummy_css,
return 0;
+out_put_css:
+ css_put(event->css);
out_put_cfile:
fput(cfile);
out_put_eventfd:
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