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편집 파일: cgroup-defs.h

/* SPDX-License-Identifier: GPL-2.0 */ /* * linux/cgroup-defs.h - basic definitions for cgroup * * This file provides basic type and interface. Include this file directly * only if necessary to avoid cyclic dependencies. */ #ifndef _LINUX_CGROUP_DEFS_H #define _LINUX_CGROUP_DEFS_H #include <linux/limits.h> #include <linux/list.h> #include <linux/idr.h> #include <linux/wait.h> #include <linux/mutex.h> #include <linux/rcupdate.h> #include <linux/refcount.h> #include <linux/percpu-refcount.h> #include <linux/percpu-rwsem.h> #include <linux/u64_stats_sync.h> #include <linux/workqueue.h> #include <linux/bpf-cgroup-defs.h> #include <linux/psi_types.h> #include <linux/rh_kabi.h> #ifdef CONFIG_CGROUPS struct cgroup; struct cgroup_root; struct cgroup_subsys; struct cgroup_taskset; struct kernfs_node; struct kernfs_ops; struct kernfs_open_file; struct seq_file; struct poll_table_struct; #define MAX_CGROUP_TYPE_NAMELEN 32 #define MAX_CGROUP_ROOT_NAMELEN 64 #define MAX_CFTYPE_NAME 64 /* define the enumeration of all cgroup subsystems */ #define SUBSYS(_x) _x ## _cgrp_id, enum cgroup_subsys_id { #include <linux/cgroup_subsys.h> CGROUP_SUBSYS_COUNT, }; #undef SUBSYS /* bits in struct cgroup_subsys_state flags field */ enum { CSS_NO_REF = (1 << 0), /* no reference counting for this css */ CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */ CSS_RELEASED = (1 << 2), /* refcnt reached zero, released */ CSS_VISIBLE = (1 << 3), /* css is visible to userland */ CSS_DYING = (1 << 4), /* css is dying */ }; /* bits in struct cgroup flags field */ enum { /* Control Group requires release notifications to userspace */ CGRP_NOTIFY_ON_RELEASE, /* * Clone the parent's configuration when creating a new child * cpuset cgroup. For historical reasons, this option can be * specified at mount time and thus is implemented here. */ CGRP_CPUSET_CLONE_CHILDREN, /* Control group has to be frozen. */ CGRP_FREEZE, /* Cgroup is frozen. */ CGRP_FROZEN, /* Control group has to be killed. */ CGRP_KILL, }; /* cgroup_root->flags */ enum { CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */ CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */ /* * Consider namespaces as delegation boundaries. If this flag is * set, controller specific interface files in a namespace root * aren't writeable from inside the namespace. */ CGRP_ROOT_NS_DELEGATE = (1 << 3), /* * Reduce latencies on dynamic cgroup modifications such as task * migrations and controller on/offs by disabling percpu operation on * cgroup_threadgroup_rwsem. This makes hot path operations such as * forks and exits into the slow path and more expensive. * * The static usage pattern of creating a cgroup, enabling controllers, * and then seeding it with CLONE_INTO_CGROUP doesn't require write * locking cgroup_threadgroup_rwsem and thus doesn't benefit from * favordynmod. */ CGRP_ROOT_FAVOR_DYNMODS = (1 << 4), /* * Enable cpuset controller in v1 cgroup to use v2 behavior. */ CGRP_ROOT_CPUSET_V2_MODE = (1 << 16), /* * Enable legacy local memory.events. */ CGRP_ROOT_MEMORY_LOCAL_EVENTS = (1 << 17), /* * Enable recursive subtree protection */ CGRP_ROOT_MEMORY_RECURSIVE_PROT = (1 << 18), }; /* cftype->flags */ enum { CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */ CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */ CFTYPE_NS_DELEGATABLE = (1 << 2), /* writeable beyond delegation boundaries */ CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */ CFTYPE_WORLD_WRITABLE = (1 << 4), /* (DON'T USE FOR NEW FILES) S_IWUGO */ CFTYPE_DEBUG = (1 << 5), /* create when cgroup_debug */ /* internal flags, do not use outside cgroup core proper */ __CFTYPE_ONLY_ON_DFL = (1 << 16), /* only on default hierarchy */ __CFTYPE_NOT_ON_DFL = (1 << 17), /* not on default hierarchy */ __CFTYPE_ADDED = (1 << 18), }; /* * cgroup_file is the handle for a file instance created in a cgroup which * is used, for example, to generate file changed notifications. This can * be obtained by setting cftype->file_offset. */ struct cgroup_file { /* do not access any fields from outside cgroup core */ struct kernfs_node *kn; unsigned long notified_at; struct timer_list notify_timer; }; /* * Per-subsystem/per-cgroup state maintained by the system. This is the * fundamental structural building block that controllers deal with. * * Fields marked with "PI:" are public and immutable and may be accessed * directly without synchronization. */ struct cgroup_subsys_state { /* PI: the cgroup that this css is attached to */ struct cgroup *cgroup; /* PI: the cgroup subsystem that this css is attached to */ struct cgroup_subsys *ss; /* reference count - access via css_[try]get() and css_put() */ struct percpu_ref refcnt; /* siblings list anchored at the parent's ->children */ struct list_head sibling; struct list_head children; /* flush target list anchored at cgrp->rstat_css_list */ struct list_head rstat_css_node; /* * PI: Subsys-unique ID. 0 is unused and root is always 1. The * matching css can be looked up using css_from_id(). */ int id; unsigned int flags; /* * Monotonically increasing unique serial number which defines a * uniform order among all csses. It's guaranteed that all * ->children lists are in the ascending order of ->serial_nr and * used to allow interrupting and resuming iterations. */ u64 serial_nr; /* * Incremented by online self and children. Used to guarantee that * parents are not offlined before their children. */ atomic_t online_cnt; /* percpu_ref killing and RCU release */ struct work_struct destroy_work; struct rcu_work destroy_rwork; /* * PI: the parent css. Placed here for cache proximity to following * fields of the containing structure. */ struct cgroup_subsys_state *parent; }; /* * A css_set is a structure holding pointers to a set of * cgroup_subsys_state objects. This saves space in the task struct * object and speeds up fork()/exit(), since a single inc/dec and a * list_add()/del() can bump the reference count on the entire cgroup * set for a task. */ struct css_set { /* * Set of subsystem states, one for each subsystem. This array is * immutable after creation apart from the init_css_set during * subsystem registration (at boot time). */ struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT]; /* reference count */ refcount_t refcount; /* * For a domain cgroup, the following points to self. If threaded, * to the matching cset of the nearest domain ancestor. The * dom_cset provides access to the domain cgroup and its csses to * which domain level resource consumptions should be charged. */ struct css_set *dom_cset; /* the default cgroup associated with this css_set */ struct cgroup *dfl_cgrp; /* internal task count, protected by css_set_lock */ int nr_tasks; /* * Lists running through all tasks using this cgroup group. * mg_tasks lists tasks which belong to this cset but are in the * process of being migrated out or in. Protected by * css_set_rwsem, but, during migration, once tasks are moved to * mg_tasks, it can be read safely while holding cgroup_mutex. */ struct list_head tasks; struct list_head mg_tasks; struct list_head dying_tasks; /* all css_task_iters currently walking this cset */ struct list_head task_iters; /* * On the default hierarchy, ->subsys[ssid] may point to a css * attached to an ancestor instead of the cgroup this css_set is * associated with. The following node is anchored at * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to * iterate through all css's attached to a given cgroup. */ struct list_head e_cset_node[CGROUP_SUBSYS_COUNT]; /* all threaded csets whose ->dom_cset points to this cset */ struct list_head threaded_csets; struct list_head threaded_csets_node; /* * List running through all cgroup groups in the same hash * slot. Protected by css_set_lock */ struct hlist_node hlist; /* * List of cgrp_cset_links pointing at cgroups referenced from this * css_set. Protected by css_set_lock. */ struct list_head cgrp_links; /* * List of csets participating in the on-going migration either as * source or destination. Protected by cgroup_mutex. */ struct list_head mg_src_preload_node; struct list_head mg_dst_preload_node; struct list_head mg_node; /* * If this cset is acting as the source of migration the following * two fields are set. mg_src_cgrp and mg_dst_cgrp are * respectively the source and destination cgroups of the on-going * migration. mg_dst_cset is the destination cset the target tasks * on this cset should be migrated to. Protected by cgroup_mutex. */ struct cgroup *mg_src_cgrp; struct cgroup *mg_dst_cgrp; struct css_set *mg_dst_cset; /* dead and being drained, ignore for migration */ bool dead; /* For RCU-protected deletion */ struct rcu_head rcu_head; }; struct cgroup_base_stat { struct task_cputime cputime; #ifdef CONFIG_SCHED_CORE u64 forceidle_sum; #endif }; /* * rstat - cgroup scalable recursive statistics. Accounting is done * per-cpu in cgroup_rstat_cpu which is then lazily propagated up the * hierarchy on reads. * * When a stat gets updated, the cgroup_rstat_cpu and its ancestors are * linked into the updated tree. On the following read, propagation only * considers and consumes the updated tree. This makes reading O(the * number of descendants which have been active since last read) instead of * O(the total number of descendants). * * This is important because there can be a lot of (draining) cgroups which * aren't active and stat may be read frequently. The combination can * become very expensive. By propagating selectively, increasing reading * frequency decreases the cost of each read. * * This struct hosts both the fields which implement the above - * updated_children and updated_next - and the fields which track basic * resource statistics on top of it - bsync, bstat and last_bstat. */ struct cgroup_rstat_cpu { /* * ->bsync protects ->bstat. These are the only fields which get * updated in the hot path. */ struct u64_stats_sync bsync; struct cgroup_base_stat bstat; /* * Snapshots at the last reading. These are used to calculate the * deltas to propagate to the global counters. */ struct cgroup_base_stat last_bstat; /* * Child cgroups with stat updates on this cpu since the last read * are linked on the parent's ->updated_children through * ->updated_next. * * In addition to being more compact, singly-linked list pointing * to the cgroup makes it unnecessary for each per-cpu struct to * point back to the associated cgroup. * * Protected by per-cpu cgroup_rstat_cpu_lock. */ struct cgroup *updated_children; /* terminated by self cgroup */ struct cgroup *updated_next; /* NULL iff not on the list */ }; struct cgroup_freezer_state { /* Should the cgroup and its descendants be frozen. */ bool freeze; /* Should the cgroup actually be frozen? */ int e_freeze; /* Fields below are protected by css_set_lock */ /* Number of frozen descendant cgroups */ int nr_frozen_descendants; /* * Number of tasks, which are counted as frozen: * frozen, SIGSTOPped, and PTRACEd. */ int nr_frozen_tasks; }; struct cgroup { /* self css with NULL ->ss, points back to this cgroup */ struct cgroup_subsys_state self; unsigned long flags; /* "unsigned long" so bitops work */ /* * The depth this cgroup is at. The root is at depth zero and each * step down the hierarchy increments the level. This along with * ancestors[] can determine whether a given cgroup is a * descendant of another without traversing the hierarchy. */ int level; /* Maximum allowed descent tree depth */ int max_depth; /* * Keep track of total numbers of visible and dying descent cgroups. * Dying cgroups are cgroups which were deleted by a user, * but are still existing because someone else is holding a reference. * max_descendants is a maximum allowed number of descent cgroups. * * nr_descendants and nr_dying_descendants are protected * by cgroup_mutex and css_set_lock. It's fine to read them holding * any of cgroup_mutex and css_set_lock; for writing both locks * should be held. */ int nr_descendants; int nr_dying_descendants; int max_descendants; /* * Each non-empty css_set associated with this cgroup contributes * one to nr_populated_csets. The counter is zero iff this cgroup * doesn't have any tasks. * * All children which have non-zero nr_populated_csets and/or * nr_populated_children of their own contribute one to either * nr_populated_domain_children or nr_populated_threaded_children * depending on their type. Each counter is zero iff all cgroups * of the type in the subtree proper don't have any tasks. */ int nr_populated_csets; int nr_populated_domain_children; int nr_populated_threaded_children; int nr_threaded_children; /* # of live threaded child cgroups */ struct kernfs_node *kn; /* cgroup kernfs entry */ struct cgroup_file procs_file; /* handle for "cgroup.procs" */ struct cgroup_file events_file; /* handle for "cgroup.events" */ /* * The bitmask of subsystems enabled on the child cgroups. * ->subtree_control is the one configured through * "cgroup.subtree_control" while ->subtree_ss_mask is the effective * one which may have more subsystems enabled. Controller knobs * are made available iff it's enabled in ->subtree_control. */ u16 subtree_control; u16 subtree_ss_mask; u16 old_subtree_control; u16 old_subtree_ss_mask; /* Private pointers for each registered subsystem */ struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT]; struct cgroup_root *root; /* * List of cgrp_cset_links pointing at css_sets with tasks in this * cgroup. Protected by css_set_lock. */ struct list_head cset_links; /* * On the default hierarchy, a css_set for a cgroup with some * susbsys disabled will point to css's which are associated with * the closest ancestor which has the subsys enabled. The * following lists all css_sets which point to this cgroup's css * for the given subsystem. */ struct list_head e_csets[CGROUP_SUBSYS_COUNT]; /* * If !threaded, self. If threaded, it points to the nearest * domain ancestor. Inside a threaded subtree, cgroups are exempt * from process granularity and no-internal-task constraint. * Domain level resource consumptions which aren't tied to a * specific task are charged to the dom_cgrp. */ struct cgroup *dom_cgrp; struct cgroup *old_dom_cgrp; /* used while enabling threaded */ /* per-cpu recursive resource statistics */ struct cgroup_rstat_cpu __percpu *rstat_cpu; struct list_head rstat_css_list; /* * Add padding to separate the read mostly rstat_cpu and * rstat_css_list into a different cacheline from the following * rstat_flush_next and *bstat fields which can have frequent updates. */ CACHELINE_PADDING(_pad_); /* * A singly-linked list of cgroup structures to be rstat flushed. * This is a scratch field to be used exclusively by * cgroup_rstat_flush_locked() and protected by cgroup_rstat_lock. */ struct cgroup *rstat_flush_next; /* cgroup basic resource statistics */ struct cgroup_base_stat last_bstat; struct cgroup_base_stat bstat; struct prev_cputime prev_cputime; /* for printing out cputime */ /* * list of pidlists, up to two for each namespace (one for procs, one * for tasks); created on demand. */ struct list_head pidlists; struct mutex pidlist_mutex; /* used to wait for offlining of csses */ wait_queue_head_t offline_waitq; /* used to schedule release agent */ struct work_struct release_agent_work; /* used to track pressure stalls */ struct psi_group *psi; /* used to store eBPF programs */ RH_KABI_EXCLUDE_WITH_SIZE(struct cgroup_bpf bpf, 256) /* If there is block congestion on this cgroup. */ atomic_t congestion_count; /* Used to store internal freezer state */ struct cgroup_freezer_state freezer; #ifdef CONFIG_BPF_SYSCALL RH_KABI_EXCLUDE(struct bpf_local_storage __rcu *bpf_cgrp_storage) #endif /* All ancestors including self */ struct cgroup *ancestors[]; }; /* * A cgroup_root represents the root of a cgroup hierarchy, and may be * associated with a kernfs_root to form an active hierarchy. This is * internal to cgroup core. Don't access directly from controllers. */ struct cgroup_root { struct kernfs_root *kf_root; /* The bitmask of subsystems attached to this hierarchy */ unsigned int subsys_mask; /* Unique id for this hierarchy. */ int hierarchy_id; /* * The root cgroup. The containing cgroup_root will be destroyed on its * release. cgrp->ancestors[0] will be used overflowing into the * following field. cgrp_ancestor_storage must immediately follow. */ struct cgroup cgrp; /* must follow cgrp for cgrp->ancestors[0], see above */ struct cgroup *cgrp_ancestor_storage; /* Number of cgroups in the hierarchy, used only for /proc/cgroups */ atomic_t nr_cgrps; /* A list running through the active hierarchies */ struct list_head root_list; /* Hierarchy-specific flags */ unsigned int flags; /* The path to use for release notifications. */ char release_agent_path[PATH_MAX]; /* The name for this hierarchy - may be empty */ char name[MAX_CGROUP_ROOT_NAMELEN]; }; /* * struct cftype: handler definitions for cgroup control files * * When reading/writing to a file: * - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata * - the 'cftype' of the file is file->f_path.dentry->d_fsdata */ struct cftype { /* * By convention, the name should begin with the name of the * subsystem, followed by a period. Zero length string indicates * end of cftype array. */ char name[MAX_CFTYPE_NAME]; unsigned long private; /* * The maximum length of string, excluding trailing nul, that can * be passed to write. If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed. */ size_t max_write_len; /* CFTYPE_* flags */ unsigned int flags; /* * If non-zero, should contain the offset from the start of css to * a struct cgroup_file field. cgroup will record the handle of * the created file into it. The recorded handle can be used as * long as the containing css remains accessible. */ unsigned int file_offset; /* * Fields used for internal bookkeeping. Initialized automatically * during registration. */ struct cgroup_subsys *ss; /* NULL for cgroup core files */ struct list_head node; /* anchored at ss->cfts */ struct kernfs_ops *kf_ops; int (*open)(struct kernfs_open_file *of); void (*release)(struct kernfs_open_file *of); /* * read_u64() is a shortcut for the common case of returning a * single integer. Use it in place of read() */ u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft); /* * read_s64() is a signed version of read_u64() */ s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft); /* generic seq_file read interface */ int (*seq_show)(struct seq_file *sf, void *v); /* optional ops, implement all or none */ void *(*seq_start)(struct seq_file *sf, loff_t *ppos); void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos); void (*seq_stop)(struct seq_file *sf, void *v); /* * write_u64() is a shortcut for the common case of accepting * a single integer (as parsed by simple_strtoull) from * userspace. Use in place of write(); return 0 or error. */ int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft, u64 val); /* * write_s64() is a signed version of write_u64() */ int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft, s64 val); /* * write() is the generic write callback which maps directly to * kernfs write operation and overrides all other operations. * Maximum write size is determined by ->max_write_len. Use * of_css/cft() to access the associated css and cft. */ ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off); __poll_t (*poll)(struct kernfs_open_file *of, struct poll_table_struct *pt); #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lock_class_key lockdep_key; #endif }; /* * Control Group subsystem type. * See Documentation/admin-guide/cgroup-v1/cgroups.rst for details */ struct cgroup_subsys { struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css); int (*css_online)(struct cgroup_subsys_state *css); void (*css_offline)(struct cgroup_subsys_state *css); void (*css_released)(struct cgroup_subsys_state *css); void (*css_free)(struct cgroup_subsys_state *css); void (*css_reset)(struct cgroup_subsys_state *css); void (*css_rstat_flush)(struct cgroup_subsys_state *css, int cpu); int (*css_extra_stat_show)(struct seq_file *seq, struct cgroup_subsys_state *css); int (*can_attach)(struct cgroup_taskset *tset); void (*cancel_attach)(struct cgroup_taskset *tset); void (*attach)(struct cgroup_taskset *tset); void (*post_attach)(void); int (*can_fork)(struct task_struct *task, struct css_set *cset); void (*cancel_fork)(struct task_struct *task, struct css_set *cset); void (*fork)(struct task_struct *task); void (*exit)(struct task_struct *task); void (*release)(struct task_struct *task); void (*bind)(struct cgroup_subsys_state *root_css); bool early_init:1; /* * If %true, the controller, on the default hierarchy, doesn't show * up in "cgroup.controllers" or "cgroup.subtree_control", is * implicitly enabled on all cgroups on the default hierarchy, and * bypasses the "no internal process" constraint. This is for * utility type controllers which is transparent to userland. * * An implicit controller can be stolen from the default hierarchy * anytime and thus must be okay with offline csses from previous * hierarchies coexisting with csses for the current one. */ bool implicit_on_dfl:1; /* * If %true, the controller, supports threaded mode on the default * hierarchy. In a threaded subtree, both process granularity and * no-internal-process constraint are ignored and a threaded * controllers should be able to handle that. * * Note that as an implicit controller is automatically enabled on * all cgroups on the default hierarchy, it should also be * threaded. implicit && !threaded is not supported. */ bool threaded:1; /* the following two fields are initialized automatically 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 * * 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 * * 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) { might_sleep(); } 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. */ struct sock_cgroup_data { struct cgroup *cgroup; /* v2 */ #ifdef CONFIG_CGROUP_NET_CLASSID u32 classid; /* v1 */ #endif #ifdef CONFIG_CGROUP_NET_PRIO u16 prioidx; /* v1 */ #endif }; static inline u16 sock_cgroup_prioidx(const struct sock_cgroup_data *skcd) { #ifdef CONFIG_CGROUP_NET_PRIO return READ_ONCE(skcd->prioidx); #else return 1; #endif } static inline u32 sock_cgroup_classid(const struct sock_cgroup_data *skcd) { #ifdef CONFIG_CGROUP_NET_CLASSID return READ_ONCE(skcd->classid); #else return 0; #endif } static inline void sock_cgroup_set_prioidx(struct sock_cgroup_data *skcd, u16 prioidx) { #ifdef CONFIG_CGROUP_NET_PRIO WRITE_ONCE(skcd->prioidx, prioidx); #endif } static inline void sock_cgroup_set_classid(struct sock_cgroup_data *skcd, u32 classid) { #ifdef CONFIG_CGROUP_NET_CLASSID WRITE_ONCE(skcd->classid, classid); #endif } #else /* CONFIG_SOCK_CGROUP_DATA */ struct sock_cgroup_data { }; #endif /* CONFIG_SOCK_CGROUP_DATA */ #endif /* _LINUX_CGROUP_DEFS_H */