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Merge branch 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 

Pull cgroup changes from Tejun Heo:
 "Nothing too interesting.  A minor bug fix and some cleanups."

* 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Update remount documentation
  cgroup: cgroup_rm_files() was calling simple_unlink() with the wrong inode
  cgroup: Remove populate() documentation
  cgroup: remove hierarchy_mutex
This commit is contained in:
Linus Torvalds 2012-07-24 17:47:44 -07:00
parent a08489c569 9a8054aa5d
commit 614a6d4341
3 changed files with 10 additions and 81 deletions
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27
Documentation/cgroups/cgroups.txt
View File

@ -370,15 +370,12 @@ To mount a cgroup hierarchy with just the cpuset and memory
subsystems, type:
# mount -t cgroup -o cpuset,memory hier1 /sys/fs/cgroup/rg1
To change the set of subsystems bound to a mounted hierarchy, just
remount with different options:
# mount -o remount,cpuset,blkio hier1 /sys/fs/cgroup/rg1
Now memory is removed from the hierarchy and blkio is added.
Note this will add blkio to the hierarchy but won't remove memory or
cpuset, because the new options are appended to the old ones:
# mount -o remount,blkio /sys/fs/cgroup/rg1
While remounting cgroups is currently supported, it is not recommend
to use it. Remounting allows changing bound subsystems and
release_agent. Rebinding is hardly useful as it only works when the
hierarchy is empty and release_agent itself should be replaced with
conventional fsnotify. The support for remounting will be removed in
the future.
To Specify a hierarchy's release_agent:
# mount -t cgroup -o cpuset,release_agent="/sbin/cpuset_release_agent" \
@ -637,16 +634,6 @@ void exit(struct task_struct *task)
Called during task exit.
int populate(struct cgroup *cgrp)
(cgroup_mutex held by caller)
Called after creation of a cgroup to allow a subsystem to populate
the cgroup directory with file entries. The subsystem should make
calls to cgroup_add_file() with objects of type cftype (see
include/linux/cgroup.h for details). Note that although this
method can return an error code, the error code is currently not
always handled well.
void post_clone(struct cgroup *cgrp)
(cgroup_mutex held by caller)
@ -656,7 +643,7 @@ example in cpusets, no task may attach before 'cpus' and 'mems' are set
up.
void bind(struct cgroup *root)
(cgroup_mutex and ss->hierarchy_mutex held by caller)
(cgroup_mutex held by caller)
Called when a cgroup subsystem is rebound to a different hierarchy
and root cgroup. Currently this will only involve movement between

17
include/linux/cgroup.h
View File

@ -499,22 +499,9 @@ struct cgroup_subsys {
#define MAX_CGROUP_TYPE_NAMELEN 32
const char *name;
/*
* Protects sibling/children links of cgroups in this
* hierarchy, plus protects which hierarchy (or none) the
* subsystem is a part of (i.e. root/sibling). To avoid
* potential deadlocks, the following operations should not be
* undertaken while holding any hierarchy_mutex:
*
* - allocating memory
* - initiating hotplug events
*/
struct mutex hierarchy_mutex;
struct lock_class_key subsys_key;
/*
* Link to parent, and list entry in parent's children.
* Protected by this->hierarchy_mutex and cgroup_lock()
* Protected by cgroup_lock()
*/
struct cgroupfs_root *root;
struct list_head sibling;
@ -602,7 +589,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
* the lifetime of cgroup_subsys_state is subsys's matter.
*
* Looking up and scanning function should be called under rcu_read_lock().
* Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
* Taking cgroup_mutex is not necessary for following calls.
* But the css returned by this routine can be "not populated yet" or "being
* destroyed". The caller should check css and cgroup's status.
*/

47
kernel/cgroup.c
View File

@ -954,7 +954,7 @@ static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
dget(d);
d_delete(d);
simple_unlink(d->d_inode, d);
simple_unlink(cgrp->dentry->d_inode, d);
list_del_init(&cfe->node);
dput(d);
@ -1068,28 +1068,24 @@ static int rebind_subsystems(struct cgroupfs_root *root,
BUG_ON(cgrp->subsys[i]);
BUG_ON(!dummytop->subsys[i]);
BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
mutex_lock(&ss->hierarchy_mutex);
cgrp->subsys[i] = dummytop->subsys[i];
cgrp->subsys[i]->cgroup = cgrp;
list_move(&ss->sibling, &root->subsys_list);
ss->root = root;
if (ss->bind)
ss->bind(cgrp);
mutex_unlock(&ss->hierarchy_mutex);
/* refcount was already taken, and we're keeping it */
} else if (bit & removed_bits) {
/* We're removing this subsystem */
BUG_ON(ss == NULL);
BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
mutex_lock(&ss->hierarchy_mutex);
if (ss->bind)
ss->bind(dummytop);
dummytop->subsys[i]->cgroup = dummytop;
cgrp->subsys[i] = NULL;
subsys[i]->root = &rootnode;
list_move(&ss->sibling, &rootnode.subsys_list);
mutex_unlock(&ss->hierarchy_mutex);
/* subsystem is now free - drop reference on module */
module_put(ss->module);
} else if (bit & final_bits) {
@ -3915,37 +3911,6 @@ static void init_cgroup_css(struct cgroup_subsys_state *css,
set_bit(CSS_CLEAR_CSS_REFS, &css->flags);
}
static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
{
/* We need to take each hierarchy_mutex in a consistent order */
int i;
/*
* No worry about a race with rebind_subsystems that might mess up the
* locking order, since both parties are under cgroup_mutex.
*/
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss == NULL)
continue;
if (ss->root == root)
mutex_lock(&ss->hierarchy_mutex);
}
}
static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
{
int i;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss == NULL)
continue;
if (ss->root == root)
mutex_unlock(&ss->hierarchy_mutex);
}
}
/*
* cgroup_create - create a cgroup
* @parent: cgroup that will be parent of the new cgroup
@ -4006,9 +3971,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
ss->post_clone(cgrp);
}
cgroup_lock_hierarchy(root);
list_add(&cgrp->sibling, &cgrp->parent->children);
cgroup_unlock_hierarchy(root);
root->number_of_cgroups++;
err = cgroup_create_dir(cgrp, dentry, mode);
@ -4035,9 +3998,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
err_remove:
cgroup_lock_hierarchy(root);
list_del(&cgrp->sibling);
cgroup_unlock_hierarchy(root);
root->number_of_cgroups--;
err_destroy:
@ -4245,10 +4206,8 @@ again:
list_del_init(&cgrp->release_list);
raw_spin_unlock(&release_list_lock);
cgroup_lock_hierarchy(cgrp->root);
/* delete this cgroup from parent->children */
list_del_init(&cgrp->sibling);
cgroup_unlock_hierarchy(cgrp->root);
list_del_init(&cgrp->allcg_node);
@ -4322,8 +4281,6 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
* need to invoke fork callbacks here. */
BUG_ON(!list_empty(&init_task.tasks));
mutex_init(&ss->hierarchy_mutex);
lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
ss->active = 1;
/* this function shouldn't be used with modular subsystems, since they
@ -4450,8 +4407,6 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
}
write_unlock(&css_set_lock);
mutex_init(&ss->hierarchy_mutex);
lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
ss->active = 1;
/* success! */