#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
#include <linux/flex_array.h> /* used in cgroup_attach_task */
#include <linux/kthread.h>
+#include <linux/delay.h>
#include <linux/atomic.h>
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
bool is_add);
static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
+static void cgroup_enable_task_cg_lists(void);
/**
* cgroup_css - obtain a cgroup's css for the specified subsystem
* fork()/exit() overhead for people who have cgroups compiled into their
* kernel but not actually in use.
*/
-static int use_task_css_set_links __read_mostly;
+static bool use_task_css_set_links __read_mostly;
static void __put_css_set(struct css_set *cset, int taskexit)
{
}
}
-static void cgroup_get_root(struct cgroupfs_root *root)
-{
- /*
- * The caller must ensure that @root is alive, which can be
- * achieved by holding a ref on one of the member cgroups or
- * following a registered reference to @root while holding
- * cgroup_tree_mutex.
- */
- WARN_ON_ONCE(atomic_read(&root->refcnt) <= 0);
- atomic_inc(&root->refcnt);
-}
-
-static void cgroup_put_root(struct cgroupfs_root *root)
+static void cgroup_destroy_root(struct cgroupfs_root *root)
{
struct cgroup *cgrp = &root->top_cgroup;
struct cgrp_cset_link *link, *tmp_link;
- int ret;
- /*
- * @root's refcnt reaching zero and its deregistration should be
- * atomic w.r.t. cgroup_tree_mutex. This ensures that
- * cgroup_get_root() is safe to invoke if @root is registered.
- */
mutex_lock(&cgroup_tree_mutex);
- if (!atomic_dec_and_test(&root->refcnt)) {
- mutex_unlock(&cgroup_tree_mutex);
- return;
- }
mutex_lock(&cgroup_mutex);
- BUG_ON(atomic_read(&root->nr_cgrps) != 1);
+ BUG_ON(atomic_read(&root->nr_cgrps));
BUG_ON(!list_empty(&cgrp->children));
/* Rebind all subsystems back to the default hierarchy */
- if (root->flags & CGRP_ROOT_SUBSYS_BOUND) {
- ret = rebind_subsystems(root, 0, root->subsys_mask);
- /* Shouldn't be able to fail ... */
- BUG_ON(ret);
- }
+ WARN_ON(rebind_subsystems(root, 0, root->subsys_mask));
/*
* Release all the links from cset_links to this hierarchy's
struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
atomic_dec(&cgrp->root->nr_cgrps);
-
- /*
- * We get a ref to the parent, and put the ref when this cgroup is
- * being freed, so it's guaranteed that the parent won't be
- * destroyed before its children.
- */
- cgroup_put(cgrp->parent);
-
- /* put the root reference that we took when we created the cgroup */
- cgroup_put_root(cgrp->root);
-
cgroup_pidlist_destroy_all(cgrp);
- kernfs_put(cgrp->kn);
- kfree(cgrp);
+ if (cgrp->parent) {
+ /*
+ * We get a ref to the parent, and put the ref when this
+ * cgroup is being freed, so it's guaranteed that the
+ * parent won't be destroyed before its children.
+ */
+ cgroup_put(cgrp->parent);
+ kernfs_put(cgrp->kn);
+ kfree(cgrp);
+ } else {
+ /*
+ * This is top cgroup's refcnt reaching zero, which
+ * indicates that the root should be released.
+ */
+ cgroup_destroy_root(cgrp->root);
+ }
}
static void cgroup_free_rcu(struct rcu_head *head)
{
if (!atomic_dec_and_test(&cgrp->refcnt))
return;
- if (WARN_ON_ONCE(!cgroup_is_dead(cgrp)))
+ if (WARN_ON_ONCE(cgrp->parent && !cgroup_is_dead(cgrp)))
return;
/*
}
}
- /*
- * Mark @root has finished binding subsystems. @root->subsys_mask
- * now matches the bound subsystems.
- */
- root->flags |= CGRP_ROOT_SUBSYS_BOUND;
kernfs_activate(cgrp->kn);
-
return 0;
}
if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
- if (opts->flags & CGRP_ROOT_NOPREFIX) {
- pr_err("cgroup: sane_behavior: noprefix is not allowed\n");
+ if ((opts->flags & (CGRP_ROOT_NOPREFIX | CGRP_ROOT_XATTR)) ||
+ opts->cpuset_clone_children || opts->release_agent ||
+ opts->name) {
+ pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n");
return -EINVAL;
}
-
- if (opts->cpuset_clone_children) {
- pr_err("cgroup: sane_behavior: clone_children is not allowed\n");
- return -EINVAL;
- }
-
- if (opts->flags & CGRP_ROOT_XATTR)
- pr_warning("cgroup: sane_behavior: xattr is always available, flag unnecessary\n");
}
/*
{
struct cgroup *cgrp = &root->top_cgroup;
- atomic_set(&root->refcnt, 1);
INIT_LIST_HEAD(&root->root_list);
atomic_set(&root->nr_cgrps, 1);
cgrp->root = root;
init_cgroup_root(root);
- /*
- * We need to set @root->subsys_mask now so that @root can be
- * matched by cgroup_test_super() before it finishes
- * initialization; otherwise, competing mounts with the same
- * options may try to bind the same subsystems instead of waiting
- * for the first one leading to unexpected mount errors.
- * SUBSYS_BOUND will be set once actual binding is complete.
- */
- root->subsys_mask = opts->subsys_mask;
root->flags = opts->flags;
if (opts->release_agent)
strcpy(root->release_agent_path, opts->release_agent);
return root;
}
-static int cgroup_setup_root(struct cgroupfs_root *root)
+static int cgroup_setup_root(struct cgroupfs_root *root, unsigned long ss_mask)
{
LIST_HEAD(tmp_links);
struct cgroup *root_cgrp = &root->top_cgroup;
if (ret)
goto destroy_root;
- ret = rebind_subsystems(root, root->subsys_mask, 0);
+ ret = rebind_subsystems(root, ss_mask, 0);
if (ret)
goto destroy_root;
struct dentry *dentry;
int ret;
+ /*
+ * The first time anyone tries to mount a cgroup, enable the list
+ * linking each css_set to its tasks and fix up all existing tasks.
+ */
+ if (!use_task_css_set_links)
+ cgroup_enable_task_cg_lists();
+retry:
mutex_lock(&cgroup_tree_mutex);
mutex_lock(&cgroup_mutex);
}
}
- cgroup_get_root(root);
+ /*
+ * A root's lifetime is governed by its top cgroup. Zero
+ * ref indicate that the root is being destroyed. Wait for
+ * destruction to complete so that the subsystems are free.
+ * We can use wait_queue for the wait but this path is
+ * super cold. Let's just sleep for a bit and retry.
+ */
+ if (!atomic_inc_not_zero(&root->top_cgroup.refcnt)) {
+ mutex_unlock(&cgroup_mutex);
+ mutex_unlock(&cgroup_tree_mutex);
+ msleep(10);
+ goto retry;
+ }
+
+ ret = 0;
goto out_unlock;
}
goto out_unlock;
}
- ret = cgroup_setup_root(root);
+ ret = cgroup_setup_root(root, opts.subsys_mask);
if (ret)
cgroup_free_root(root);
dentry = kernfs_mount(fs_type, flags, root->kf_root);
if (IS_ERR(dentry))
- cgroup_put_root(root);
+ cgroup_put(&root->top_cgroup);
return dentry;
}
struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
struct cgroupfs_root *root = cgroup_root_from_kf(kf_root);
- cgroup_put_root(root);
+ cgroup_put(&root->top_cgroup);
kernfs_kill_sb(sb);
}
rcu_assign_pointer(tsk->cgroups, new_cset);
task_unlock(tsk);
- /* Update the css_set linked lists if we're using them */
write_lock(&css_set_lock);
- if (!list_empty(&tsk->cg_list))
- list_move(&tsk->cg_list, &new_cset->tasks);
+ list_move(&tsk->cg_list, &new_cset->tasks);
write_unlock(&css_set_lock);
/*
* To reduce the fork() overhead for systems that are not actually using
* their cgroups capability, we don't maintain the lists running through
* each css_set to its tasks until we see the list actually used - in other
- * words after the first call to css_task_iter_start().
+ * words after the first mount.
*/
static void cgroup_enable_task_cg_lists(void)
{
struct task_struct *p, *g;
+
write_lock(&css_set_lock);
- use_task_css_set_links = 1;
+
+ if (use_task_css_set_links)
+ goto out_unlock;
+
+ use_task_css_set_links = true;
+
/*
* We need tasklist_lock because RCU is not safe against
* while_each_thread(). Besides, a forking task that has passed
read_lock(&tasklist_lock);
do_each_thread(g, p) {
task_lock(p);
+
+ WARN_ON_ONCE(!list_empty(&p->cg_list) ||
+ task_css_set(p) != &init_css_set);
+
/*
* We should check if the process is exiting, otherwise
* it will race with cgroup_exit() in that the list
* entry won't be deleted though the process has exited.
*/
- if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
+ if (!(p->flags & PF_EXITING))
list_add(&p->cg_list, &task_css_set(p)->tasks);
+
task_unlock(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
+out_unlock:
write_unlock(&css_set_lock);
}
struct css_task_iter *it)
__acquires(css_set_lock)
{
- /*
- * The first time anyone tries to iterate across a css, we need to
- * enable the list linking each css_set to its tasks, and fix up
- * all existing tasks.
- */
- if (!use_task_css_set_links)
- cgroup_enable_task_cg_lists();
+ /* no one should try to iterate before mounting cgroups */
+ WARN_ON_ONCE(!use_task_css_set_links);
read_lock(&css_set_lock);
/* allocation complete, commit to creation */
list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
atomic_inc(&root->nr_cgrps);
-
- /*
- * Grab a reference on the root and parent so that they don't get
- * deleted while there are child cgroups.
- */
- cgroup_get_root(root);
cgroup_get(parent);
/*
projects / firefly-linux-kernel-4.4.55.git / blobdiff