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cgroup: Set CGRP_RELEASABLE when adding to a cgroup

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Changes the meaning of CGRP_RELEASABLE to be set on any cgroup
that has ever had a task or cgroup in it, or had css_get called
on it.  The bit is set in cgroup_attach_task, cgroup_create,
and __css_get.  It is not necessary to set the bit in
cgroup_fork, as the task is either in the root cgroup, in
which can never be released, or the task it was forked from
already set the bit in croup_attach_task.

Signed-off-by: Colin Cross <ccross@android.com>
This commit is contained in:
Colin Cross 2010-11-23 21:37:03 -08:00
parent a05f03bf6e
commit 60cdbd1f33
2 changed files with 25 additions and 41 deletions
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12
include/linux/cgroup.h
View File

@ -84,12 +84,6 @@ enum {
CSS_REMOVED, /* This CSS is dead */
};
/* Caller must verify that the css is not for root cgroup */
static inline void __css_get(struct cgroup_subsys_state *css, int count)
{
atomic_add(count, &css->refcnt);
}
/*
* Call css_get() to hold a reference on the css; it can be used
* for a reference obtained via:
@ -97,6 +91,7 @@ static inline void __css_get(struct cgroup_subsys_state *css, int count)
* - task->cgroups for a locked task
*/
extern void __css_get(struct cgroup_subsys_state *css, int count);
static inline void css_get(struct cgroup_subsys_state *css)
{
/* We don't need to reference count the root state */
@ -143,10 +138,7 @@ static inline void css_put(struct cgroup_subsys_state *css)
enum {
/* Control Group is dead */
CGRP_REMOVED,
/*
* Control Group has previously had a child cgroup or a task,
* but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
*/
/* Control Group has ever had a child cgroup or a task */
CGRP_RELEASABLE,
/* Control Group requires release notifications to userspace */
CGRP_NOTIFY_ON_RELEASE,

54
kernel/cgroup.c
View File

@ -335,7 +335,15 @@ static void free_css_set_rcu(struct rcu_head *obj)
* compiled into their kernel but not actually in use */
static int use_task_css_set_links __read_mostly;
static void __put_css_set(struct css_set *cg, int taskexit)
/*
* refcounted get/put for css_set objects
*/
static inline void get_css_set(struct css_set *cg)
{
atomic_inc(&cg->refcount);
}
static void put_css_set(struct css_set *cg)
{
struct cg_cgroup_link *link;
struct cg_cgroup_link *saved_link;
@ -361,12 +369,8 @@ static void __put_css_set(struct css_set *cg, int taskexit)
struct cgroup *cgrp = link->cgrp;
list_del(&link->cg_link_list);
list_del(&link->cgrp_link_list);
if (atomic_dec_and_test(&cgrp->count) &&
notify_on_release(cgrp)) {
if (taskexit)
set_bit(CGRP_RELEASABLE, &cgrp->flags);
if (atomic_dec_and_test(&cgrp->count))
check_for_release(cgrp);
}
kfree(link);
}
@ -375,24 +379,6 @@ static void __put_css_set(struct css_set *cg, int taskexit)
call_rcu(&cg->rcu_head, free_css_set_rcu);
}
/*
* refcounted get/put for css_set objects
*/
static inline void get_css_set(struct css_set *cg)
{
atomic_inc(&cg->refcount);
}
static inline void put_css_set(struct css_set *cg)
{
__put_css_set(cg, 0);
}
static inline void put_css_set_taskexit(struct css_set *cg)
{
__put_css_set(cg, 1);
}
/*
* compare_css_sets - helper function for find_existing_css_set().
* @cg: candidate css_set being tested
@ -1773,7 +1759,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
if (ss->attach)
ss->attach(ss, cgrp, oldcgrp, tsk, false);
}
set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
set_bit(CGRP_RELEASABLE, &cgrp->flags);
synchronize_rcu();
put_css_set(cg);
@ -3361,6 +3347,8 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
if (err < 0)
goto err_remove;
set_bit(CGRP_RELEASABLE, &parent->flags);
/* The cgroup directory was pre-locked for us */
BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
@ -3579,7 +3567,6 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
cgroup_d_remove_dir(d);
dput(d);
set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
/*
@ -4174,7 +4161,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
tsk->cgroups = &init_css_set;
task_unlock(tsk);
if (cg)
put_css_set_taskexit(cg);
put_css_set(cg);
}
/**
@ -4343,6 +4330,14 @@ static void check_for_release(struct cgroup *cgrp)
}
}
/* Caller must verify that the css is not for root cgroup */
void __css_get(struct cgroup_subsys_state *css, int count)
{
atomic_add(count, &css->refcnt);
set_bit(CGRP_RELEASABLE, &css->cgroup->flags);
}
EXPORT_SYMBOL_GPL(__css_get);
/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css, int count)
{
@ -4351,10 +4346,7 @@ void __css_put(struct cgroup_subsys_state *css, int count)
rcu_read_lock();
val = atomic_sub_return(count, &css->refcnt);
if (val == 1) {
if (notify_on_release(cgrp)) {
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
}
check_for_release(cgrp);
cgroup_wakeup_rmdir_waiter(cgrp);
}
rcu_read_unlock();