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![Tejun Heo](/assets/img/avatar_default.png)
Since e93ad19d05
("cpuset: make mm migration asynchronous"), cpuset
kicks off asynchronous NUMA node migration if necessary during task
migration and flushes it from cpuset_post_attach_flush() which is
called at the end of __cgroup_procs_write(). This is to avoid
performing migration with cgroup_threadgroup_rwsem write-locked which
can lead to deadlock through dependency on kworker creation.
memcg has a similar issue with charge moving, so let's convert it to
an official callback rather than the current one-off cpuset specific
function. This patch adds cgroup_subsys->post_attach callback and
makes cpuset register cpuset_post_attach_flush() as its ->post_attach.
The conversion is mostly one-to-one except that the new callback is
called under cgroup_mutex. This is to guarantee that no other
migration operations are started before ->post_attach callbacks are
finished. cgroup_mutex is one of the outermost mutex in the system
and has never been and shouldn't be a problem. We can add specialized
synchronization around __cgroup_procs_write() but I don't think
there's any noticeable benefit.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <stable@vger.kernel.org> # 4.4+ prerequisite for the next patch
668 lines
20 KiB
C
668 lines
20 KiB
C
/*
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* linux/cgroup-defs.h - basic definitions for cgroup
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*
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* This file provides basic type and interface. Include this file directly
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* only if necessary to avoid cyclic dependencies.
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*/
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#ifndef _LINUX_CGROUP_DEFS_H
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#define _LINUX_CGROUP_DEFS_H
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#include <linux/limits.h>
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#include <linux/list.h>
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#include <linux/idr.h>
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#include <linux/wait.h>
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#include <linux/mutex.h>
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#include <linux/rcupdate.h>
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#include <linux/percpu-refcount.h>
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#include <linux/percpu-rwsem.h>
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#include <linux/workqueue.h>
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#ifdef CONFIG_CGROUPS
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struct cgroup;
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struct cgroup_root;
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struct cgroup_subsys;
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struct cgroup_taskset;
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struct kernfs_node;
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struct kernfs_ops;
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struct kernfs_open_file;
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struct seq_file;
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#define MAX_CGROUP_TYPE_NAMELEN 32
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#define MAX_CGROUP_ROOT_NAMELEN 64
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#define MAX_CFTYPE_NAME 64
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/* define the enumeration of all cgroup subsystems */
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#define SUBSYS(_x) _x ## _cgrp_id,
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enum cgroup_subsys_id {
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#include <linux/cgroup_subsys.h>
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CGROUP_SUBSYS_COUNT,
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};
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#undef SUBSYS
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/* bits in struct cgroup_subsys_state flags field */
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enum {
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CSS_NO_REF = (1 << 0), /* no reference counting for this css */
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CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
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CSS_RELEASED = (1 << 2), /* refcnt reached zero, released */
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CSS_VISIBLE = (1 << 3), /* css is visible to userland */
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};
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/* bits in struct cgroup flags field */
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enum {
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/* Control Group requires release notifications to userspace */
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CGRP_NOTIFY_ON_RELEASE,
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/*
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* Clone the parent's configuration when creating a new child
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* cpuset cgroup. For historical reasons, this option can be
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* specified at mount time and thus is implemented here.
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*/
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CGRP_CPUSET_CLONE_CHILDREN,
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};
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/* cgroup_root->flags */
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enum {
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CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
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CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
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};
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/* cftype->flags */
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enum {
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CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */
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CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */
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CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
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CFTYPE_WORLD_WRITABLE = (1 << 4), /* (DON'T USE FOR NEW FILES) S_IWUGO */
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/* internal flags, do not use outside cgroup core proper */
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__CFTYPE_ONLY_ON_DFL = (1 << 16), /* only on default hierarchy */
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__CFTYPE_NOT_ON_DFL = (1 << 17), /* not on default hierarchy */
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};
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/*
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* cgroup_file is the handle for a file instance created in a cgroup which
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* is used, for example, to generate file changed notifications. This can
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* be obtained by setting cftype->file_offset.
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*/
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struct cgroup_file {
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/* do not access any fields from outside cgroup core */
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struct kernfs_node *kn;
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};
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/*
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* Per-subsystem/per-cgroup state maintained by the system. This is the
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* fundamental structural building block that controllers deal with.
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*
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* Fields marked with "PI:" are public and immutable and may be accessed
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* directly without synchronization.
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*/
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struct cgroup_subsys_state {
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/* PI: the cgroup that this css is attached to */
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struct cgroup *cgroup;
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/* PI: the cgroup subsystem that this css is attached to */
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struct cgroup_subsys *ss;
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/* reference count - access via css_[try]get() and css_put() */
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struct percpu_ref refcnt;
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/* PI: the parent css */
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struct cgroup_subsys_state *parent;
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/* siblings list anchored at the parent's ->children */
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struct list_head sibling;
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struct list_head children;
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/*
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* PI: Subsys-unique ID. 0 is unused and root is always 1. The
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* matching css can be looked up using css_from_id().
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*/
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int id;
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unsigned int flags;
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/*
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* Monotonically increasing unique serial number which defines a
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* uniform order among all csses. It's guaranteed that all
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* ->children lists are in the ascending order of ->serial_nr and
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* used to allow interrupting and resuming iterations.
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*/
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u64 serial_nr;
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/*
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* Incremented by online self and children. Used to guarantee that
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* parents are not offlined before their children.
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*/
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atomic_t online_cnt;
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/* percpu_ref killing and RCU release */
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struct rcu_head rcu_head;
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struct work_struct destroy_work;
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};
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/*
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* A css_set is a structure holding pointers to a set of
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* cgroup_subsys_state objects. This saves space in the task struct
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* object and speeds up fork()/exit(), since a single inc/dec and a
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* list_add()/del() can bump the reference count on the entire cgroup
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* set for a task.
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*/
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struct css_set {
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/* Reference count */
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atomic_t refcount;
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/*
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* List running through all cgroup groups in the same hash
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* slot. Protected by css_set_lock
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*/
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struct hlist_node hlist;
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/*
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* Lists running through all tasks using this cgroup group.
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* mg_tasks lists tasks which belong to this cset but are in the
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* process of being migrated out or in. Protected by
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* css_set_rwsem, but, during migration, once tasks are moved to
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* mg_tasks, it can be read safely while holding cgroup_mutex.
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*/
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struct list_head tasks;
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struct list_head mg_tasks;
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/*
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* List of cgrp_cset_links pointing at cgroups referenced from this
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* css_set. Protected by css_set_lock.
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*/
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struct list_head cgrp_links;
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/* the default cgroup associated with this css_set */
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struct cgroup *dfl_cgrp;
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/*
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* Set of subsystem states, one for each subsystem. This array is
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* immutable after creation apart from the init_css_set during
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* subsystem registration (at boot time).
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*/
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struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
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/*
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* List of csets participating in the on-going migration either as
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* source or destination. Protected by cgroup_mutex.
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*/
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struct list_head mg_preload_node;
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struct list_head mg_node;
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/*
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* If this cset is acting as the source of migration the following
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* two fields are set. mg_src_cgrp and mg_dst_cgrp are
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* respectively the source and destination cgroups of the on-going
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* migration. mg_dst_cset is the destination cset the target tasks
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* on this cset should be migrated to. Protected by cgroup_mutex.
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*/
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struct cgroup *mg_src_cgrp;
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struct cgroup *mg_dst_cgrp;
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struct css_set *mg_dst_cset;
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/*
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* On the default hierarhcy, ->subsys[ssid] may point to a css
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* attached to an ancestor instead of the cgroup this css_set is
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* associated with. The following node is anchored at
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* ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
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* iterate through all css's attached to a given cgroup.
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*/
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struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];
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/* all css_task_iters currently walking this cset */
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struct list_head task_iters;
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/* dead and being drained, ignore for migration */
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bool dead;
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/* For RCU-protected deletion */
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struct rcu_head rcu_head;
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};
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struct cgroup {
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/* self css with NULL ->ss, points back to this cgroup */
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struct cgroup_subsys_state self;
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unsigned long flags; /* "unsigned long" so bitops work */
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/*
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* idr allocated in-hierarchy ID.
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*
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* ID 0 is not used, the ID of the root cgroup is always 1, and a
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* new cgroup will be assigned with a smallest available ID.
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*
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* Allocating/Removing ID must be protected by cgroup_mutex.
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*/
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int id;
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/*
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* The depth this cgroup is at. The root is at depth zero and each
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* step down the hierarchy increments the level. This along with
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* ancestor_ids[] can determine whether a given cgroup is a
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* descendant of another without traversing the hierarchy.
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*/
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int level;
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/*
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* Each non-empty css_set associated with this cgroup contributes
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* one to populated_cnt. All children with non-zero popuplated_cnt
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* of their own contribute one. The count is zero iff there's no
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* task in this cgroup or its subtree.
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*/
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int populated_cnt;
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struct kernfs_node *kn; /* cgroup kernfs entry */
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struct cgroup_file procs_file; /* handle for "cgroup.procs" */
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struct cgroup_file events_file; /* handle for "cgroup.events" */
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/*
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* The bitmask of subsystems enabled on the child cgroups.
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* ->subtree_control is the one configured through
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* "cgroup.subtree_control" while ->child_ss_mask is the effective
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* one which may have more subsystems enabled. Controller knobs
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* are made available iff it's enabled in ->subtree_control.
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*/
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u16 subtree_control;
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u16 subtree_ss_mask;
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u16 old_subtree_control;
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u16 old_subtree_ss_mask;
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/* Private pointers for each registered subsystem */
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struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
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struct cgroup_root *root;
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/*
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* List of cgrp_cset_links pointing at css_sets with tasks in this
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* cgroup. Protected by css_set_lock.
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*/
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struct list_head cset_links;
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/*
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* On the default hierarchy, a css_set for a cgroup with some
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* susbsys disabled will point to css's which are associated with
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* the closest ancestor which has the subsys enabled. The
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* following lists all css_sets which point to this cgroup's css
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* for the given subsystem.
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*/
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struct list_head e_csets[CGROUP_SUBSYS_COUNT];
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/*
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* list of pidlists, up to two for each namespace (one for procs, one
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* for tasks); created on demand.
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*/
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struct list_head pidlists;
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struct mutex pidlist_mutex;
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/* used to wait for offlining of csses */
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wait_queue_head_t offline_waitq;
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/* used to schedule release agent */
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struct work_struct release_agent_work;
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/* ids of the ancestors at each level including self */
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int ancestor_ids[];
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};
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/*
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* A cgroup_root represents the root of a cgroup hierarchy, and may be
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* associated with a kernfs_root to form an active hierarchy. This is
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* internal to cgroup core. Don't access directly from controllers.
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*/
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struct cgroup_root {
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struct kernfs_root *kf_root;
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/* The bitmask of subsystems attached to this hierarchy */
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unsigned int subsys_mask;
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/* Unique id for this hierarchy. */
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int hierarchy_id;
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/* The root cgroup. Root is destroyed on its release. */
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struct cgroup cgrp;
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/* for cgrp->ancestor_ids[0] */
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int cgrp_ancestor_id_storage;
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/* Number of cgroups in the hierarchy, used only for /proc/cgroups */
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atomic_t nr_cgrps;
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/* A list running through the active hierarchies */
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struct list_head root_list;
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/* Hierarchy-specific flags */
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unsigned int flags;
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/* IDs for cgroups in this hierarchy */
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struct idr cgroup_idr;
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/* The path to use for release notifications. */
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char release_agent_path[PATH_MAX];
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/* The name for this hierarchy - may be empty */
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char name[MAX_CGROUP_ROOT_NAMELEN];
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};
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/*
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* struct cftype: handler definitions for cgroup control files
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*
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* When reading/writing to a file:
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* - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata
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* - the 'cftype' of the file is file->f_path.dentry->d_fsdata
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*/
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struct cftype {
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/*
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* By convention, the name should begin with the name of the
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* subsystem, followed by a period. Zero length string indicates
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* end of cftype array.
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*/
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char name[MAX_CFTYPE_NAME];
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unsigned long private;
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/*
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* The maximum length of string, excluding trailing nul, that can
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* be passed to write. If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
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*/
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size_t max_write_len;
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/* CFTYPE_* flags */
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unsigned int flags;
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/*
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* If non-zero, should contain the offset from the start of css to
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* a struct cgroup_file field. cgroup will record the handle of
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* the created file into it. The recorded handle can be used as
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* long as the containing css remains accessible.
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*/
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unsigned int file_offset;
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/*
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* Fields used for internal bookkeeping. Initialized automatically
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* during registration.
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*/
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struct cgroup_subsys *ss; /* NULL for cgroup core files */
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struct list_head node; /* anchored at ss->cfts */
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struct kernfs_ops *kf_ops;
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/*
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* read_u64() is a shortcut for the common case of returning a
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* single integer. Use it in place of read()
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*/
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u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
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/*
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* read_s64() is a signed version of read_u64()
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*/
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s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
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/* generic seq_file read interface */
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int (*seq_show)(struct seq_file *sf, void *v);
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/* optional ops, implement all or none */
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void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
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void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
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void (*seq_stop)(struct seq_file *sf, void *v);
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/*
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* write_u64() is a shortcut for the common case of accepting
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* a single integer (as parsed by simple_strtoull) from
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* userspace. Use in place of write(); return 0 or error.
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*/
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int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
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u64 val);
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/*
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* write_s64() is a signed version of write_u64()
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*/
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int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
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s64 val);
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/*
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* write() is the generic write callback which maps directly to
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* kernfs write operation and overrides all other operations.
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* Maximum write size is determined by ->max_write_len. Use
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* of_css/cft() to access the associated css and cft.
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*/
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ssize_t (*write)(struct kernfs_open_file *of,
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char *buf, size_t nbytes, loff_t off);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lock_class_key lockdep_key;
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#endif
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};
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/*
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* Control Group subsystem type.
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* See Documentation/cgroups/cgroups.txt for details
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*/
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struct cgroup_subsys {
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struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
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int (*css_online)(struct cgroup_subsys_state *css);
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void (*css_offline)(struct cgroup_subsys_state *css);
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void (*css_released)(struct cgroup_subsys_state *css);
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void (*css_free)(struct cgroup_subsys_state *css);
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void (*css_reset)(struct cgroup_subsys_state *css);
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int (*can_attach)(struct cgroup_taskset *tset);
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void (*cancel_attach)(struct cgroup_taskset *tset);
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void (*attach)(struct cgroup_taskset *tset);
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void (*post_attach)(void);
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int (*can_fork)(struct task_struct *task);
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void (*cancel_fork)(struct task_struct *task);
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void (*fork)(struct task_struct *task);
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void (*exit)(struct task_struct *task);
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void (*free)(struct task_struct *task);
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void (*bind)(struct cgroup_subsys_state *root_css);
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bool early_init:1;
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/*
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* If %true, the controller, on the default hierarchy, doesn't show
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* up in "cgroup.controllers" or "cgroup.subtree_control", is
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* implicitly enabled on all cgroups on the default hierarchy, and
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* bypasses the "no internal process" constraint. This is for
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* utility type controllers which is transparent to userland.
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*
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* An implicit controller can be stolen from the default hierarchy
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* anytime and thus must be okay with offline csses from previous
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* hierarchies coexisting with csses for the current one.
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*/
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bool implicit_on_dfl:1;
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/*
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* If %false, this subsystem is properly hierarchical -
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* configuration, resource accounting and restriction on a parent
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* cgroup cover those of its children. If %true, hierarchy support
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* is broken in some ways - some subsystems ignore hierarchy
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* completely while others are only implemented half-way.
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*
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* It's now disallowed to create nested cgroups if the subsystem is
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* broken and cgroup core will emit a warning message on such
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* cases. Eventually, all subsystems will be made properly
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* hierarchical and this will go away.
|
|
*/
|
|
bool broken_hierarchy:1;
|
|
bool warned_broken_hierarchy:1;
|
|
|
|
/* the following two fields are initialized automtically during boot */
|
|
int id;
|
|
const char *name;
|
|
|
|
/* optional, initialized automatically during boot if not set */
|
|
const char *legacy_name;
|
|
|
|
/* link to parent, protected by cgroup_lock() */
|
|
struct cgroup_root *root;
|
|
|
|
/* idr for css->id */
|
|
struct idr css_idr;
|
|
|
|
/*
|
|
* List of cftypes. Each entry is the first entry of an array
|
|
* terminated by zero length name.
|
|
*/
|
|
struct list_head cfts;
|
|
|
|
/*
|
|
* Base cftypes which are automatically registered. The two can
|
|
* point to the same array.
|
|
*/
|
|
struct cftype *dfl_cftypes; /* for the default hierarchy */
|
|
struct cftype *legacy_cftypes; /* for the legacy hierarchies */
|
|
|
|
/*
|
|
* A subsystem may depend on other subsystems. When such subsystem
|
|
* is enabled on a cgroup, the depended-upon subsystems are enabled
|
|
* together if available. Subsystems enabled due to dependency are
|
|
* not visible to userland until explicitly enabled. The following
|
|
* specifies the mask of subsystems that this one depends on.
|
|
*/
|
|
unsigned int depends_on;
|
|
};
|
|
|
|
extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
|
|
|
|
/**
|
|
* cgroup_threadgroup_change_begin - threadgroup exclusion for cgroups
|
|
* @tsk: target task
|
|
*
|
|
* Called from threadgroup_change_begin() and allows cgroup operations to
|
|
* synchronize against threadgroup changes using a percpu_rw_semaphore.
|
|
*/
|
|
static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
|
|
{
|
|
percpu_down_read(&cgroup_threadgroup_rwsem);
|
|
}
|
|
|
|
/**
|
|
* cgroup_threadgroup_change_end - threadgroup exclusion for cgroups
|
|
* @tsk: target task
|
|
*
|
|
* Called from threadgroup_change_end(). Counterpart of
|
|
* cgroup_threadcgroup_change_begin().
|
|
*/
|
|
static inline void cgroup_threadgroup_change_end(struct task_struct *tsk)
|
|
{
|
|
percpu_up_read(&cgroup_threadgroup_rwsem);
|
|
}
|
|
|
|
#else /* CONFIG_CGROUPS */
|
|
|
|
#define CGROUP_SUBSYS_COUNT 0
|
|
|
|
static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk) {}
|
|
static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {}
|
|
|
|
#endif /* CONFIG_CGROUPS */
|
|
|
|
#ifdef CONFIG_SOCK_CGROUP_DATA
|
|
|
|
/*
|
|
* sock_cgroup_data is embedded at sock->sk_cgrp_data and contains
|
|
* per-socket cgroup information except for memcg association.
|
|
*
|
|
* On legacy hierarchies, net_prio and net_cls controllers directly set
|
|
* attributes on each sock which can then be tested by the network layer.
|
|
* On the default hierarchy, each sock is associated with the cgroup it was
|
|
* created in and the networking layer can match the cgroup directly.
|
|
*
|
|
* To avoid carrying all three cgroup related fields separately in sock,
|
|
* sock_cgroup_data overloads (prioidx, classid) and the cgroup pointer.
|
|
* On boot, sock_cgroup_data records the cgroup that the sock was created
|
|
* in so that cgroup2 matches can be made; however, once either net_prio or
|
|
* net_cls starts being used, the area is overriden to carry prioidx and/or
|
|
* classid. The two modes are distinguished by whether the lowest bit is
|
|
* set. Clear bit indicates cgroup pointer while set bit prioidx and
|
|
* classid.
|
|
*
|
|
* While userland may start using net_prio or net_cls at any time, once
|
|
* either is used, cgroup2 matching no longer works. There is no reason to
|
|
* mix the two and this is in line with how legacy and v2 compatibility is
|
|
* handled. On mode switch, cgroup references which are already being
|
|
* pointed to by socks may be leaked. While this can be remedied by adding
|
|
* synchronization around sock_cgroup_data, given that the number of leaked
|
|
* cgroups is bound and highly unlikely to be high, this seems to be the
|
|
* better trade-off.
|
|
*/
|
|
struct sock_cgroup_data {
|
|
union {
|
|
#ifdef __LITTLE_ENDIAN
|
|
struct {
|
|
u8 is_data;
|
|
u8 padding;
|
|
u16 prioidx;
|
|
u32 classid;
|
|
} __packed;
|
|
#else
|
|
struct {
|
|
u32 classid;
|
|
u16 prioidx;
|
|
u8 padding;
|
|
u8 is_data;
|
|
} __packed;
|
|
#endif
|
|
u64 val;
|
|
};
|
|
};
|
|
|
|
/*
|
|
* There's a theoretical window where the following accessors race with
|
|
* updaters and return part of the previous pointer as the prioidx or
|
|
* classid. Such races are short-lived and the result isn't critical.
|
|
*/
|
|
static inline u16 sock_cgroup_prioidx(struct sock_cgroup_data *skcd)
|
|
{
|
|
/* fallback to 1 which is always the ID of the root cgroup */
|
|
return (skcd->is_data & 1) ? skcd->prioidx : 1;
|
|
}
|
|
|
|
static inline u32 sock_cgroup_classid(struct sock_cgroup_data *skcd)
|
|
{
|
|
/* fallback to 0 which is the unconfigured default classid */
|
|
return (skcd->is_data & 1) ? skcd->classid : 0;
|
|
}
|
|
|
|
/*
|
|
* If invoked concurrently, the updaters may clobber each other. The
|
|
* caller is responsible for synchronization.
|
|
*/
|
|
static inline void sock_cgroup_set_prioidx(struct sock_cgroup_data *skcd,
|
|
u16 prioidx)
|
|
{
|
|
struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
|
|
|
|
if (sock_cgroup_prioidx(&skcd_buf) == prioidx)
|
|
return;
|
|
|
|
if (!(skcd_buf.is_data & 1)) {
|
|
skcd_buf.val = 0;
|
|
skcd_buf.is_data = 1;
|
|
}
|
|
|
|
skcd_buf.prioidx = prioidx;
|
|
WRITE_ONCE(skcd->val, skcd_buf.val); /* see sock_cgroup_ptr() */
|
|
}
|
|
|
|
static inline void sock_cgroup_set_classid(struct sock_cgroup_data *skcd,
|
|
u32 classid)
|
|
{
|
|
struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
|
|
|
|
if (sock_cgroup_classid(&skcd_buf) == classid)
|
|
return;
|
|
|
|
if (!(skcd_buf.is_data & 1)) {
|
|
skcd_buf.val = 0;
|
|
skcd_buf.is_data = 1;
|
|
}
|
|
|
|
skcd_buf.classid = classid;
|
|
WRITE_ONCE(skcd->val, skcd_buf.val); /* see sock_cgroup_ptr() */
|
|
}
|
|
|
|
#else /* CONFIG_SOCK_CGROUP_DATA */
|
|
|
|
struct sock_cgroup_data {
|
|
};
|
|
|
|
#endif /* CONFIG_SOCK_CGROUP_DATA */
|
|
|
|
#endif /* _LINUX_CGROUP_DEFS_H */
|