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authorZefan Li <lizefan@huawei.com>2014-09-19 16:51:00 +0800
committerTejun Heo <tj@kernel.org>2014-09-19 09:29:32 -0400
commita25eb52e81a40e986179a790fbb5a1f02f482b7a (patch)
tree1d88c2bfdd17f168a5c21b4038d697148187d958 /kernel/cgroup.c
parent4e2ba65068ac1d0e8c9df78a4ad787cf39640418 (diff)
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cgroup: remove CGRP_RELEASABLE flag
We call put_css_set() after setting CGRP_RELEASABLE flag in cgroup_task_migrate(), but in other places we call it without setting the flag. I don't see the necessity of this flag. Moreover once the flag is set, it will never be cleared, unless writing to the notify_on_release control file, so it can be quite confusing if we look at the output of debug.releasable. # mount -t cgroup -o debug xxx /cgroup # mkdir /cgroup/child # cat /cgroup/child/debug.releasable 0 <-- shows 0 though the cgroup is empty # echo $$ > /cgroup/child/tasks # cat /cgroup/child/debug.releasable 0 # echo $$ > /cgroup/tasks && echo $$ > /cgroup/child/tasks # cat /proc/child/debug.releasable 1 <-- shows 1 though the cgroup is not empty This patch removes the flag, and now debug.releasable shows if the cgroup is empty or not. Signed-off-by: Zefan Li <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c40
1 files changed, 13 insertions, 27 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index df7733b48d2e..16e3a4f5c9dc 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -329,14 +329,6 @@ bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
return false;
}
-static int cgroup_is_releasable(const struct cgroup *cgrp)
-{
- const int bits =
- (1 << CGRP_RELEASABLE) |
- (1 << CGRP_NOTIFY_ON_RELEASE);
- return (cgrp->flags & bits) == bits;
-}
-
static int notify_on_release(const struct cgroup *cgrp)
{
return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
@@ -491,7 +483,7 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
return key;
}
-static void put_css_set_locked(struct css_set *cset, bool taskexit)
+static void put_css_set_locked(struct css_set *cset)
{
struct cgrp_cset_link *link, *tmp_link;
struct cgroup_subsys *ss;
@@ -517,11 +509,7 @@ static void put_css_set_locked(struct css_set *cset, bool taskexit)
/* @cgrp can't go away while we're holding css_set_rwsem */
if (list_empty(&cgrp->cset_links)) {
cgroup_update_populated(cgrp, false);
- if (notify_on_release(cgrp)) {
- if (taskexit)
- set_bit(CGRP_RELEASABLE, &cgrp->flags);
- check_for_release(cgrp);
- }
+ check_for_release(cgrp);
}
kfree(link);
@@ -530,7 +518,7 @@ static void put_css_set_locked(struct css_set *cset, bool taskexit)
kfree_rcu(cset, rcu_head);
}
-static void put_css_set(struct css_set *cset, bool taskexit)
+static void put_css_set(struct css_set *cset)
{
/*
* Ensure that the refcount doesn't hit zero while any readers
@@ -541,7 +529,7 @@ static void put_css_set(struct css_set *cset, bool taskexit)
return;
down_write(&css_set_rwsem);
- put_css_set_locked(cset, taskexit);
+ put_css_set_locked(cset);
up_write(&css_set_rwsem);
}
@@ -2037,8 +2025,7 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
* task. As trading it for new_cset is protected by cgroup_mutex,
* we're safe to drop it here; it will be freed under RCU.
*/
- set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
- put_css_set_locked(old_cset, false);
+ put_css_set_locked(old_cset);
}
/**
@@ -2059,7 +2046,7 @@ static void cgroup_migrate_finish(struct list_head *preloaded_csets)
cset->mg_src_cgrp = NULL;
cset->mg_dst_cset = NULL;
list_del_init(&cset->mg_preload_node);
- put_css_set_locked(cset, false);
+ put_css_set_locked(cset);
}
up_write(&css_set_rwsem);
}
@@ -2153,8 +2140,8 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
if (src_cset == dst_cset) {
src_cset->mg_src_cgrp = NULL;
list_del_init(&src_cset->mg_preload_node);
- put_css_set(src_cset, false);
- put_css_set(dst_cset, false);
+ put_css_set(src_cset);
+ put_css_set(dst_cset);
continue;
}
@@ -2163,7 +2150,7 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
if (list_empty(&dst_cset->mg_preload_node))
list_add(&dst_cset->mg_preload_node, &csets);
else
- put_css_set(dst_cset, false);
+ put_css_set(dst_cset);
}
list_splice_tail(&csets, preloaded_csets);
@@ -4159,7 +4146,6 @@ static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
struct cftype *cft, u64 val)
{
- clear_bit(CGRP_RELEASABLE, &css->cgroup->flags);
if (val)
set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
else
@@ -4806,7 +4792,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
*/
kernfs_remove(cgrp->kn);
- set_bit(CGRP_RELEASABLE, &cgroup_parent(cgrp)->flags);
check_for_release(cgroup_parent(cgrp));
/* put the base reference */
@@ -5244,12 +5229,12 @@ void cgroup_exit(struct task_struct *tsk)
}
if (put_cset)
- put_css_set(cset, true);
+ put_css_set(cset);
}
static void check_for_release(struct cgroup *cgrp)
{
- if (cgroup_is_releasable(cgrp) && !cgroup_has_tasks(cgrp) &&
+ if (notify_on_release(cgrp) && !cgroup_has_tasks(cgrp) &&
!css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
schedule_work(&cgrp->release_agent_work);
}
@@ -5496,7 +5481,8 @@ static int cgroup_css_links_read(struct seq_file *seq, void *v)
static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
{
- return test_bit(CGRP_RELEASABLE, &css->cgroup->flags);
+ return (!cgroup_has_tasks(css->cgroup) &&
+ !css_has_online_children(&css->cgroup->self));
}
static struct cftype debug_files[] = {