diff options
Diffstat (limited to '')
| -rw-r--r-- | Documentation/cgroups.txt | 14 | ||||
| -rw-r--r-- | include/linux/cgroup.h | 89 | ||||
| -rw-r--r-- | include/linux/sched.h | 33 | ||||
| -rw-r--r-- | kernel/cgroup.c | 649 | ||||
| -rw-r--r-- | kernel/fork.c | 1 |
5 files changed, 632 insertions, 154 deletions
diff --git a/Documentation/cgroups.txt b/Documentation/cgroups.txt index 553727cc9944..98a26f81fa75 100644 --- a/Documentation/cgroups.txt +++ b/Documentation/cgroups.txt @@ -176,7 +176,9 @@ Control Groups extends the kernel as follows: subsystem state is something that's expected to happen frequently and in performance-critical code, whereas operations that require a task's actual cgroup assignments (in particular, moving between - cgroups) are less common. + cgroups) are less common. A linked list runs through the cg_list + field of each task_struct using the css_set, anchored at + css_set->tasks. - A cgroup hierarchy filesystem can be mounted for browsing and manipulation from user space. @@ -252,6 +254,16 @@ linear search to locate an appropriate existing css_set, so isn't very efficient. A future version will use a hash table for better performance. +To allow access from a cgroup to the css_sets (and hence tasks) +that comprise it, a set of cg_cgroup_link objects form a lattice; +each cg_cgroup_link is linked into a list of cg_cgroup_links for +a single cgroup on its cont_link_list field, and a list of +cg_cgroup_links for a single css_set on its cg_link_list. + +Thus the set of tasks in a cgroup can be listed by iterating over +each css_set that references the cgroup, and sub-iterating over +each css_set's task set. + The use of a Linux virtual file system (vfs) to represent the cgroup hierarchy provides for a familiar permission and name space for cgroups, with a minimum of additional kernel code. diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index a9553568118f..836b3557bb76 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -27,10 +27,19 @@ extern void cgroup_lock(void); extern void cgroup_unlock(void); extern void cgroup_fork(struct task_struct *p); extern void cgroup_fork_callbacks(struct task_struct *p); +extern void cgroup_post_fork(struct task_struct *p); extern void cgroup_exit(struct task_struct *p, int run_callbacks); extern struct file_operations proc_cgroup_operations; +/* Define the enumeration of all cgroup subsystems */ +#define SUBSYS(_x) _x ## _subsys_id, +enum cgroup_subsys_id { +#include <linux/cgroup_subsys.h> + CGROUP_SUBSYS_COUNT +}; +#undef SUBSYS + /* Per-subsystem/per-cgroup state maintained by the system. */ struct cgroup_subsys_state { /* The cgroup that this subsystem is attached to. Useful @@ -97,6 +106,52 @@ struct cgroup { struct cgroupfs_root *root; struct cgroup *top_cgroup; + + /* + * List of cg_cgroup_links pointing at css_sets with + * tasks in this cgroup. Protected by css_set_lock + */ + struct list_head css_sets; +}; + +/* 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 { + + /* Reference count */ + struct kref ref; + + /* + * List running through all cgroup groups. Protected by + * css_set_lock + */ + struct list_head list; + + /* + * List running through all tasks using this cgroup + * group. Protected by css_set_lock + */ + struct list_head tasks; + + /* + * List of cg_cgroup_link objects on link chains from + * cgroups referenced from this css_set. Protected by + * css_set_lock + */ + struct list_head cg_links; + + /* + * 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]; + }; /* struct cftype: @@ -157,15 +212,7 @@ int cgroup_is_removed(const struct cgroup *cont); int cgroup_path(const struct cgroup *cont, char *buf, int buflen); -int __cgroup_task_count(const struct cgroup *cont); -static inline int cgroup_task_count(const struct cgroup *cont) -{ - int task_count; - rcu_read_lock(); - task_count = __cgroup_task_count(cont); - rcu_read_unlock(); - return task_count; -} +int cgroup_task_count(const struct cgroup *cont); /* Return true if the cgroup is a descendant of the current cgroup */ int cgroup_is_descendant(const struct cgroup *cont); @@ -213,7 +260,7 @@ static inline struct cgroup_subsys_state *cgroup_subsys_state( static inline struct cgroup_subsys_state *task_subsys_state( struct task_struct *task, int subsys_id) { - return rcu_dereference(task->cgroups.subsys[subsys_id]); + return rcu_dereference(task->cgroups->subsys[subsys_id]); } static inline struct cgroup* task_cgroup(struct task_struct *task, @@ -226,6 +273,27 @@ int cgroup_path(const struct cgroup *cont, char *buf, int buflen); int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss); +/* A cgroup_iter should be treated as an opaque object */ +struct cgroup_iter { + struct list_head *cg_link; + struct list_head *task; +}; + +/* To iterate across the tasks in a cgroup: + * + * 1) call cgroup_iter_start to intialize an iterator + * + * 2) call cgroup_iter_next() to retrieve member tasks until it + * returns NULL or until you want to end the iteration + * + * 3) call cgroup_iter_end() to destroy the iterator. + */ +void cgroup_iter_start(struct cgroup *cont, struct cgroup_iter *it); +struct task_struct *cgroup_iter_next(struct cgroup *cont, + struct cgroup_iter *it); +void cgroup_iter_end(struct cgroup *cont, struct cgroup_iter *it); + + #else /* !CONFIG_CGROUPS */ static inline int cgroup_init_early(void) { return 0; } @@ -233,6 +301,7 @@ static inline int cgroup_init(void) { return 0; } static inline void cgroup_init_smp(void) {} static inline void cgroup_fork(struct task_struct *p) {} static inline void cgroup_fork_callbacks(struct task_struct *p) {} +static inline void cgroup_post_fork(struct task_struct *p) {} static inline void cgroup_exit(struct task_struct *p, int callbacks) {} static inline void cgroup_lock(void) {} diff --git a/include/linux/sched.h b/include/linux/sched.h index af2ed4bae678..1aa1cfa63b37 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -894,34 +894,6 @@ struct sched_entity { #endif }; -#ifdef CONFIG_CGROUPS - -#define SUBSYS(_x) _x ## _subsys_id, -enum cgroup_subsys_id { -#include <linux/cgroup_subsys.h> - CGROUP_SUBSYS_COUNT -}; -#undef SUBSYS - -/* A css_set is a structure holding pointers to a set of - * cgroup_subsys_state objects. - */ - -struct css_set { - - /* Set of subsystem states, one for each subsystem. NULL for - * subsystems that aren't part of this hierarchy. These - * pointers reduce the number of dereferences required to get - * from a task to its state for a given cgroup, but result - * in increased space usage if tasks are in wildly different - * groupings across different hierarchies. This array is - * immutable after creation */ - struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT]; - -}; - -#endif /* CONFIG_CGROUPS */ - struct task_struct { volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */ void *stack; @@ -1159,7 +1131,10 @@ struct task_struct { int cpuset_mem_spread_rotor; #endif #ifdef CONFIG_CGROUPS - struct css_set cgroups; + /* Control Group info protected by css_set_lock */ + struct css_set *cgroups; + /* cg_list protected by css_set_lock and tsk->alloc_lock */ + struct list_head cg_list; #endif #ifdef CONFIG_FUTEX struct robust_list_head __user *robust_list; diff --git a/kernel/cgroup.c b/kernel/cgroup.c index db245f19eb8a..883928c0e147 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -36,6 +36,7 @@ #include <linux/proc_fs.h> #include <linux/rcupdate.h> #include <linux/sched.h> +#include <linux/backing-dev.h> #include <linux/seq_file.h> #include <linux/slab.h> #include <linux/magic.h> @@ -95,6 +96,7 @@ static struct cgroupfs_root rootnode; /* The list of hierarchy roots */ static LIST_HEAD(roots); +static int root_count; /* dummytop is a shorthand for the dummy hierarchy's top cgroup */ #define dummytop (&rootnode.top_cgroup) @@ -133,12 +135,49 @@ list_for_each_entry(_ss, &_root->subsys_list, sibling) #define for_each_root(_root) \ list_for_each_entry(_root, &roots, root_list) -/* Each task_struct has an embedded css_set, so the get/put - * operation simply takes a reference count on all the cgroups - * referenced by subsystems in this css_set. This can end up - * multiple-counting some cgroups, but that's OK - the ref-count is - * just a busy/not-busy indicator; ensuring that we only count each - * cgroup once would require taking a global lock to ensure that no +/* Link structure for associating css_set objects with cgroups */ +struct cg_cgroup_link { + /* + * List running through cg_cgroup_links associated with a + * cgroup, anchored on cgroup->css_sets + */ + struct list_head cont_link_list; + /* + * List running through cg_cgroup_links pointing at a + * single css_set object, anchored on css_set->cg_links + */ + struct list_head cg_link_list; + struct css_set *cg; +}; + +/* The default css_set - used by init and its children prior to any + * hierarchies being mounted. It contains a pointer to the root state + * for each subsystem. Also used to anchor the list of css_sets. Not + * reference-counted, to improve performance when child cgroups + * haven't been created. + */ + +static struct css_set init_css_set; +static struct cg_cgroup_link init_css_set_link; + +/* css_set_lock protects the list of css_set objects, and the + * chain of tasks off each css_set. Nests outside task->alloc_lock + * due to cgroup_iter_start() */ +static DEFINE_RWLOCK(css_set_lock); +static int css_set_count; + +/* We don't maintain the lists running through each css_set to its + * task until after the first call to cgroup_iter_start(). This + * reduces the fork()/exit() overhead for people who have cgroups + * compiled into their kernel but not actually in use */ +static int use_task_css_set_links; + +/* When we create or destroy a css_set, the operation simply + * takes/releases a reference count on all the cgroups referenced + * by subsystems in this css_set. This can end up multiple-counting + * some cgroups, but that's OK - the ref-count is just a + * busy/not-busy indicator; ensuring that we only count each cgroup + * once would require taking a global lock to ensure that no * subsystems moved between hierarchies while we were doing so. * * Possible TODO: decide at boot time based on the number of @@ -146,18 +185,230 @@ list_for_each_entry(_root, &roots, root_list) * it's better for performance to ref-count every subsystem, or to * take a global lock and only add one ref count to each hierarchy. */ -static void get_css_set(struct css_set *cg) + +/* + * unlink a css_set from the list and free it + */ +static void release_css_set(struct kref *k) { + struct css_set *cg = container_of(k, struct css_set, ref); int i; + + write_lock(&css_set_lock); + list_del(&cg->list); + css_set_count--; + while (!list_empty(&cg->cg_links)) { + struct cg_cgroup_link *link; + link = list_entry(cg->cg_links.next, + struct cg_cgroup_link, cg_link_list); + list_del(&link->cg_link_list); + list_del(&link->cont_link_list); + kfree(link); + } + write_unlock(&css_set_lock); for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) - atomic_inc(&cg->subsys[i]->cgroup->count); + atomic_dec(&cg->subsys[i]->cgroup->count); + kfree(cg); } -static void put_css_set(struct css_set *cg) +/* + * refcounted get/put for css_set objects + */ +static inline void get_css_set(struct css_set *cg) +{ + kref_get(&cg->ref); +} + +static inline void put_css_set(struct css_set *cg) +{ + kref_put(&cg->ref, release_css_set); +} + +/* + * find_existing_css_set() is a helper for + * find_css_set(), and checks to see whether an existing + * css_set is suitable. This currently walks a linked-list for + * simplicity; a later patch will use a hash table for better + * performance + * + * oldcg: the cgroup group that we're using before the cgroup + * transition + * + * cont: the cgroup that we're moving into + * + * template: location in which to build the desired set of subsystem + * state objects for the new cgroup group + */ + +static struct css_set *find_existing_css_set( + struct css_set *oldcg, + struct cgroup *cont, + struct cgroup_subsys_state *template[]) { int i; - for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) - atomic_dec(&cg->subsys[i]->cgroup->count); + struct cgroupfs_root *root = cont->root; + struct list_head *l = &init_css_set.list; + + /* Built the set of subsystem state objects that we want to + * see in the new css_set */ + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + if (root->subsys_bits & (1ull << i)) { + /* Subsystem is in this hierarchy. So we want + * the subsystem state from the new + * cgroup */ + template[i] = cont->subsys[i]; + } else { + /* Subsystem is not in this hierarchy, so we + * don't want to change the subsystem state */ + template[i] = oldcg->subsys[i]; + } + } + + /* Look through existing cgroup groups to find one to reuse */ + do { + struct css_set *cg = + list_entry(l, struct css_set, list); + + if (!memcmp(template, cg->subsys, sizeof(cg->subsys))) { + /* All subsystems matched */ + return cg; + } + /* Try the next cgroup group */ + l = l->next; + } while (l != &init_css_set.list); + + /* No existing cgroup group matched */ + return NULL; +} + +/* + * allocate_cg_links() allocates "count" cg_cgroup_link structures + * and chains them on tmp through their cont_link_list fields. Returns 0 on + * success or a negative error + */ + +static int allocate_cg_links(int count, struct list_head *tmp) +{ + struct cg_cgroup_link *link; + int i; + INIT_LIST_HEAD(tmp); + for (i = 0; i < count; i++) { + link = kmalloc(sizeof(*link), GFP_KERNEL); + if (!link) { + while (!list_empty(tmp)) { + link = list_entry(tmp->next, + struct cg_cgroup_link, + cont_link_list); + list_del(&link->cont_link_list); + kfree(link); + } + return -ENOMEM; + } + list_add(&link->cont_link_list, tmp); + } + return 0; +} + +static void free_cg_links(struct list_head *tmp) +{ + while (!list_empty(tmp)) { + struct cg_cgroup_link *link; + link = list_entry(tmp->next, + struct cg_cgroup_link, + cont_link_list); + list_del(&link->cont_link_list); + kfree(link); + } +} + +/* + * find_css_set() takes an existing cgroup group and a + * cgroup object, and returns a css_set object that's + * equivalent to the old group, but with the given cgroup + * substituted into the appropriate hierarchy. Must be called with + * cgroup_mutex held + */ + +static struct css_set *find_css_set( + struct css_set *oldcg, struct cgroup *cont) +{ + struct css_set *res; + struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT]; + int i; + + struct list_head tmp_cg_links; + struct cg_cgroup_link *link; + + /* First see if we already have a cgroup group that matches + * the desired set */ + write_lock(&css_set_lock); + res = find_existing_css_set(oldcg, cont, template); + if (res) + get_css_set(res); + write_unlock(&css_set_lock); + + if (res) + return res; + + res = kmalloc(sizeof(*res), GFP_KERNEL); + if (!res) + return NULL; + + /* Allocate all the cg_cgroup_link objects that we'll need */ + if (allocate_cg_links(root_count, &tmp_cg_links) < 0) { + kfree(res); + return NULL; + } + + kref_init(&res->ref); + INIT_LIST_HEAD(&res->cg_links); + INIT_LIST_HEAD(&res->tasks); + + /* Copy the set of subsystem state objects generated in + * find_existing_css_set() */ + memcpy(res->subsys, template, sizeof(res->subsys)); + + write_lock(&css_set_lock); + /* Add reference counts and links from the new css_set. */ + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup *cont = res->subsys[i]->cgroup; + struct cgroup_subsys *ss = subsys[i]; + atomic_inc(&cont->count); + /* + * We want to add a link once per cgroup, so we + * only do it for the first subsystem in each + * hierarchy + */ + if (ss->root->subsys_list.next == &ss->sibling) { + BUG_ON(list_empty(&tmp_cg_links)); + link = list_entry(tmp_cg_links.next, + struct cg_cgroup_link, + cont_link_list); + list_del(&link->cont_link_list); + list_add(&link->cont_link_list, &cont->css_sets); + link->cg = res; + list_add(&link->cg_link_list, &res->cg_links); + } + } + if (list_empty(&rootnode.subsys_list)) { + link = list_entry(tmp_cg_links.next, + struct cg_cgroup_link, + cont_link_list); + list_del(&link->cont_link_list); + list_add(&link->cont_link_list, &dummytop->css_sets); + link->cg = res; + list_add(&link->cg_link_list, &res->cg_links); + } + + BUG_ON(!list_empty(&tmp_cg_links)); + + /* Link this cgroup group into the list */ + list_add(&res->list, &init_css_set.list); + css_set_count++; + INIT_LIST_HEAD(&res->tasks); + write_unlock(&css_set_lock); + + return res; } /* @@ -504,6 +755,7 @@ static void init_cgroup_root(struct cgroupfs_root *root) cont->top_cgroup = cont; INIT_LIST_HEAD(&cont->sibling); INIT_LIST_HEAD(&cont->children); + INIT_LIST_HEAD(&cont->css_sets); } static int cgroup_test_super(struct super_block *sb, void *data) @@ -573,6 +825,8 @@ static int cgroup_get_sb(struct file_system_type *fs_type, int ret = 0; struct super_block *sb; struct cgroupfs_root *root; + struct list_head tmp_cg_links, *l; + INIT_LIST_HEAD(&tmp_cg_links); /* First find the desired set of subsystems */ ret = parse_cgroupfs_options(data, &opts); @@ -602,18 +856,36 @@ static int cgroup_get_sb(struct file_system_type *fs_type, } else { /* New superblock */ struct cgroup *cont = &root->top_cgroup; + struct inode *inode; BUG_ON(sb->s_root != NULL); ret = cgroup_get_rootdir(sb); if (ret) goto drop_new_super; + inode = sb->s_root->d_inode; + mutex_lock(&inode->i_mutex); mutex_lock(&cgroup_mutex); + /* + * We're accessing css_set_count without locking + * css_set_lock here, but that's OK - it can only be + * increased by someone holding cgroup_lock, and + * that's us. The worst that can happen is that we + * have some link structures left over + */ + ret = allocate_cg_links(css_set_count, &tmp_cg_links); + if (ret) { + mutex_unlock(&cgroup_mutex); + mutex_unlock(&inode->i_mutex); + goto drop_new_super; + } + ret = rebind_subsystems(root, root->subsys_bits); if (ret == -EBUSY) { mutex_unlock(&cgroup_mutex); + mutex_unlock(&inode->i_mutex); goto drop_new_super; } @@ -621,24 +893,40 @@ static int cgroup_get_sb(struct file_system_type *fs_type, BUG_ON(ret); list_add(&root->root_list, &roots); + root_count++; sb->s_root->d_fsdata = &root->top_cgroup; root->top_cgroup.dentry = sb->s_root; + /* Link the top cgroup in this hierarchy into all + * the css_set objects */ + write_lock(&css_set_lock); + l = &init_css_set.list; + do { + struct css_set *cg; + struct cg_cgroup_link *link; + cg = list_entry(l, struct css_set, list); + BUG_ON(list_empty(&tmp_cg_links)); + link = list_entry(tmp_cg_links.next, + struct cg_cgroup_link, + cont_link_list); + list_del(&link->cont_link_list); + link->cg = cg; + list_add(&link->cont_link_list, + &root->top_cgroup.css_sets); + list_add(&link->cg_link_list, &cg->cg_links); + l = l->next; + } while (l != &init_css_set.list); + write_unlock(&css_set_lock); + + free_cg_links(&tmp_cg_links); + BUG_ON(!list_empty(&cont->sibling)); BUG_ON(!list_empty(&cont->children)); BUG_ON(root->number_of_cgroups != 1); - /* - * I believe that it's safe to nest i_mutex inside - * cgroup_mutex in this case, since no-one else can - * be accessing this directory yet. But we still need - * to teach lockdep that this is the case - currently - * a cgroupfs remount triggers a lockdep warning - */ - mutex_lock(&cont->dentry->d_inode->i_mutex); cgroup_populate_dir(cont); - mutex_unlock(&cont->dentry->d_inode->i_mutex); + mutex_unlock(&inode->i_mutex); mutex_unlock(&cgroup_mutex); } @@ -647,6 +935,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type, drop_new_super: up_write(&sb->s_umount); deactivate_super(sb); + free_cg_links(&tmp_cg_links); return ret; } @@ -668,8 +957,25 @@ static void cgroup_kill_sb(struct super_block *sb) { /* Shouldn't be able to fail ... */ BUG_ON(ret); - if (!list_empty(&root->root_list)) + /* + * Release all the links from css_sets to this hierarchy's + * root cgroup + */ + write_lock(&css_set_lock); + while (!list_empty(&cont->css_sets)) { + struct cg_cgroup_link *link; + link = list_entry(cont->css_sets.next, + struct cg_cgroup_link, cont_link_list); + list_del(&link->cg_link_list); + list_del(&link->cont_link_list); + kfree(link); + } + write_unlock(&css_set_lock); + + if (!list_empty(&root->root_list)) { list_del(&root->root_list); + root_count--; + } mutex_unlock(&cgroup_mutex); kfree(root); @@ -762,9 +1068,9 @@ static int attach_task(struct cgroup *cont, struct task_struct *tsk) int retval = 0; struct cgroup_subsys *ss; struct cgroup *oldcont; - struct css_set *cg = &tsk->cgroups; + struct css_set *cg = tsk->cgroups; + struct css_set *newcg; struct cgroupfs_root *root = cont->root; - int i; int subsys_id; get_first_subsys(cont, NULL, &subsys_id); @@ -783,26 +1089,32 @@ static int attach_task(struct cgroup *cont, struct task_struct *tsk) } } + /* + * Locate or allocate a new css_set for this task, + * based on its final set of cgroups + */ + newcg = find_css_set(cg, cont); + if (!newcg) { + return -ENOMEM; + } + task_lock(tsk); if (tsk->flags & PF_EXITING) { task_unlock(tsk); + put_css_set(newcg); return -ESRCH; } - /* Update the css_set pointers for the subsystems in this - * hierarchy */ - for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { - if (root->subsys_bits & (1ull << i)) { - /* Subsystem is in this hierarchy. So we want - * the subsystem state from the new - * cgroup. Transfer the refcount from the - * old to the new */ - atomic_inc(&cont->count); - atomic_dec(&cg->subsys[i]->cgroup->count); - rcu_assign_pointer(cg->subsys[i], cont->subsys[i]); - } - } + rcu_assign_pointer(tsk->cgroups, newcg); 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_del(&tsk->cg_list); + list_add(&tsk->cg_list, &newcg->tasks); + } + write_unlock(&css_set_lock); + for_each_subsys(root, ss) { if (ss->attach) { ss->attach(ss, cont, oldcont, tsk); @@ -810,6 +1122,7 @@ static int attach_task(struct cgroup *cont, struct task_struct *tsk) } synchronize_rcu(); + put_css_set(cg); return 0; } @@ -1069,7 +1382,7 @@ static int cgroup_create_file(struct dentry *dentry, int mode, /* start with the directory inode held, so that we can * populate it without racing with another mkdir */ - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD); } else if (S_ISREG(mode)) { inode->i_size = 0; inode->i_fop = &cgroup_file_operations; @@ -1148,28 +1461,102 @@ int cgroup_add_files(struct cgroup *cont, return 0; } -/* Count the number of tasks in a cgroup. Could be made more - * time-efficient but less space-efficient with more linked lists - * running through each cgroup and the css_set structures that - * referenced it. Must be called with tasklist_lock held for read or - * write or in an rcu critical section. - */ -int __cgroup_task_count(const struct cgroup *cont) +/* Count the number of tasks in a cgroup. */ + +int cgroup_task_count(const struct cgroup *cont) { int count = 0; - struct task_struct *g, *p; - struct cgroup_subsys_state *css; - int subsys_id; - - get_first_subsys(cont, &css, &subsys_id); - do_each_thread(g, p) { - if (task_subsys_state(p, subsys_id) == css) - count ++; - } while_each_thread(g, p); + struct list_head *l; + + read_lock(&css_set_lock); + l = cont->css_sets.next; + while (l != &cont->css_sets) { + struct cg_cgroup_link *link = + list_entry(l, struct cg_cgroup_link, cont_link_list); + count += atomic_read(&link->cg->ref.refcount); + l = l->next; + } + read_unlock(&css_set_lock); return count; } /* + * Advance a list_head iterator. The iterator should be positioned at + * the start of a css_set + */ +static void cgroup_advance_iter(struct cgroup *cont, + struct cgroup_iter *it) +{ + struct list_head *l = it->cg_link; + struct cg_cgroup_link *link; + struct css_set *cg; + + /* Advance to the next non-empty css_set */ + do { + l = l->next; + if (l == &cont->css_sets) { + it->cg_link = NULL; + return; + } + link = list_entry(l, struct cg_cgroup_link, cont_link_list); + cg = link->cg; + } while (list_empty(&cg->tasks)); + it->cg_link = l; + it->task = cg->tasks.next; +} + +void cgroup_iter_start(struct cgroup *cont, struct cgroup_iter *it) +{ + /* + * The first time anyone tries to iterate across a cgroup, + * 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) { + struct task_struct *p, *g; + write_lock(&css_set_lock); + use_task_css_set_links = 1; + do_each_thread(g, p) { + task_lock(p); + if (list_empty(&p->cg_list)) + list_add(&p->cg_list, &p->cgroups->tasks); + task_unlock(p); + } while_each_thread(g, p); + write_unlock(&css_set_lock); + } + read_lock(&css_set_lock); + it->cg_link = &cont->css_sets; + cgroup_advance_iter(cont, it); +} + +struct task_struct *cgroup_iter_next(struct cgroup *cont, + struct cgroup_iter *it) +{ + struct task_struct *res; + struct list_head *l = it->task; + + /* If the iterator cg is NULL, we have no tasks */ + if (!it->cg_link) + return NULL; + res = list_entry(l, struct task_struct, cg_list); + /* Advance iterator to find next entry */ + l = l->next; + if (l == &res->cgroups->tasks) { + /* We reached the end of this task list - move on to + * the next cg_cgroup_link */ + cgroup_advance_iter(cont, it); + } else { + it->task = l; + } + return res; +} + +void cgroup_iter_end(struct cgroup *cont, struct cgroup_iter *it) +{ + read_unlock(&css_set_lock); +} + +/* * Stuff for reading the 'tasks' file. * * Reading this file can return large amounts of data if a cgroup has @@ -1198,22 +1585,15 @@ struct ctr_struct { static int pid_array_load(pid_t *pidarray, int npids, struct cgroup *cont) { int n = 0; - struct task_struct *g, *p; - struct cgroup_subsys_state *css; - int subsys_id; - - get_first_subsys(cont, &css, &subsys_id); - rcu_read_lock(); - do_each_thread(g, p) { - if (task_subsys_state(p, subsys_id) == css) { - pidarray[n++] = pid_nr(task_pid(p)); - if (unlikely(n == npids)) - goto array_full; - } - } while_each_thread(g, p); - -array_full: - rcu_read_unlock(); + struct cgroup_iter it; + struct task_struct *tsk; + cgroup_iter_start(cont, &it); + while ((tsk = cgroup_iter_next(cont, &it))) { + if (unlikely(n == npids)) + break; + pidarray[n++] = pid_nr(task_pid(tsk)); + } + cgroup_iter_end(cont, &it); return n; } @@ -1398,6 +1778,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, cont->flags = 0; INIT_LIST_HEAD(&cont->sibling); INIT_LIST_HEAD(&cont->children); + INIT_LIST_HEAD(&cont->css_sets); cont->parent = parent; cont->root = parent->root; @@ -1529,8 +1910,8 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry) static void cgroup_init_subsys(struct cgroup_subsys *ss) { - struct task_struct *g, *p; struct cgroup_subsys_state *css; + struct list_head *l; printk(KERN_ERR "Initializing cgroup subsys %s\n", ss->name); /* Create the top cgroup state for this subsystem */ @@ -1540,26 +1921,32 @@ static void cgroup_init_subsys(struct cgroup_subsys *ss) BUG_ON(IS_ERR(css)); init_cgroup_css(css, ss, dummytop); - /* Update all tasks to contain a subsys pointer to this state - * - since the subsystem is newly registered, all tasks are in - * the subsystem's top cgroup. */ + /* Update all cgroup groups to contain a subsys + * pointer to this state - since the subsystem is + * newly registered, all tasks and hence all cgroup + * groups are in the subsystem's top cgroup. */ + write_lock(&css_set_lock); + l = &init_css_set.list; + do { + struct css_set *cg = + list_entry(l, struct css_set, list); + cg->subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id]; + l = l->next; + } while (l != &init_css_set.list); + write_unlock(&css_set_lock); /* If this subsystem requested that it be notified with fork * events, we should send it one now for every process in the * system */ + if (ss->fork) { + struct task_struct *g, *p; - read_lock(&tasklist_lock); - init_task.cgroups.subsys[ss->subsys_id] = css; - if (ss->fork) - ss->fork(ss, &init_task); - - do_each_thread(g, p) { - printk(KERN_INFO "Setting task %p css to %p (%d)\n", css, p, p->pid); - p->cgroups.subsys[ss->subsys_id] = css; - if (ss->fork) - ss->fork(ss, p); - } while_each_thread(g, p); - read_unlock(&tasklist_lock); + read_lock(&tasklist_lock); + do_each_thread(g, p) { + ss->fork(ss, p); + } while_each_thread(g, p); + read_unlock(&tasklist_lock); + } need_forkexit_callback |= ss->fork || ss->exit; @@ -1573,8 +1960,22 @@ static void cgroup_init_subsys(struct cgroup_subsys *ss) int __init cgroup_init_early(void) { int i; + kref_init(&init_css_set.ref); + kref_get(&init_css_set.ref); + INIT_LIST_HEAD(&init_css_set.list); + INIT_LIST_HEAD(&init_css_set.cg_links); + INIT_LIST_HEAD(&init_css_set.tasks); + css_set_count = 1; init_cgroup_root(&rootnode); list_add(&rootnode.root_list, &roots); + root_count = 1; + init_task.cgroups = &init_css_set; + + init_css_set_link.cg = &init_css_set; + list_add(&init_css_set_link.cont_link_list, + &rootnode.top_cgroup.css_sets); + list_add(&init_css_set_link.cg_link_list, + &init_css_set.cg_links); for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { struct cgroup_subsys *ss = subsys[i]; @@ -1715,29 +2116,13 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v) int i; struct cgroupfs_root *root; + seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\n"); mutex_lock(&cgroup_mutex); - seq_puts(m, "Hierarchies:\n"); - for_each_root(root) { - struct cgroup_subsys *ss; - int first = 1; - seq_printf(m, "%p: bits=%lx cgroups=%d (", root, - root->subsys_bits, root->number_of_cgroups); - for_each_subsys(root, ss) { - seq_printf(m, "%s%s", first ? "" : ", ", ss->name); - first = false; - } - seq_putc(m, ')'); - if (root->sb) { - seq_printf(m, " s_active=%d", - atomic_read(&root->sb->s_active)); - } - seq_putc(m, '\n'); - } - seq_puts(m, "Subsystems:\n"); for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { struct cgroup_subsys *ss = subsys[i]; - seq_printf(m, "%d: name=%s hierarchy=%p\n", - i, ss->name, ss->root); + seq_printf(m, "%s\t%lu\t%d\n", + ss->name, ss->root->subsys_bits, + ss->root->number_of_cgroups); } mutex_unlock(&cgroup_mutex); return 0; @@ -1765,18 +2150,19 @@ static struct file_operations proc_cgroupstats_operations = { * fork.c by dup_task_struct(). However, we ignore that copy, since * it was not made under the protection of RCU or cgroup_mutex, so * might no longer be a valid cgroup pointer. attach_task() might - * have already changed current->cgroup, allowing the previously - * referenced cgroup to be removed and freed. + * have already changed current->cgroups, allowing the previously + * referenced cgroup group to be removed and freed. * * At the point that cgroup_fork() is called, 'current' is the parent * task, and the passed argument 'child' points to the child task. */ void cgroup_fork(struct task_struct *child) { - rcu_read_lock(); - child->cgroups = rcu_dereference(current->cgroups); - get_css_set(&child->cgroups); - rcu_read_unlock(); + task_lock(current); + child->cgroups = current->cgroups; + get_css_set(child->cgroups); + task_unlock(current); + INIT_LIST_HEAD(&child->cg_list); } /** @@ -1797,6 +2183,21 @@ void cgroup_fork_callbacks(struct task_struct *child) } /** + * cgroup_post_fork - called on a new task after adding it to the + * task list. Adds the task to the list running through its css_set + * if necessary. Has to be after the task is visible on the task list + * in case we race with the first call to cgroup_iter_start() - to + * guarantee that the new task ends up on its list. */ +void cgroup_post_fork(struct task_struct *child) +{ + if (use_task_css_set_links) { + write_lock(&css_set_lock); + if (list_empty(&child->cg_list)) + list_add(&child->cg_list, &child->cgroups->tasks); + write_unlock(&css_set_lock); + } +} +/** * cgroup_exit - detach cgroup from exiting task * @tsk: pointer to task_struct of exiting process * @@ -1834,6 +2235,7 @@ void cgroup_fork_callbacks(struct task_struct *child) void cgroup_exit(struct task_struct *tsk, int run_callbacks) { int i; + struct css_set *cg; if (run_callbacks && need_forkexit_callback) { for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { @@ -1842,11 +2244,26 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks) ss->exit(ss, tsk); } } + + /* + * Unlink from the css_set task list if necessary. + * Optimistically check cg_list before taking + * css_set_lock + */ + if (!list_empty(&tsk->cg_list)) { + write_lock(&css_set_lock); + if (!list_empty(&tsk->cg_list)) + list_del(&tsk->cg_list); + write_unlock(&css_set_lock); + } + /* Reassign the task to the init_css_set. */ task_lock(tsk); - put_css_set(&tsk->cgroups); - tsk->cgroups = init_task.cgroups; + cg = tsk->cgroups; + tsk->cgroups = &init_css_set; task_unlock(tsk); + if (cg) + put_css_set(cg); } /** @@ -1880,7 +2297,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys) mutex_unlock(&cgroup_mutex); return 0; } - cg = &tsk->cgroups; + cg = tsk->cgroups; parent = task_cgroup(tsk, subsys->subsys_id); snprintf(nodename, MAX_CGROUP_TYPE_NAMELEN, "node_%d", tsk->pid); @@ -1888,6 +2305,8 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys) /* Pin the hierarchy */ atomic_inc(&parent->root->sb->s_active); + /* Keep the cgroup alive */ + get_css_set(cg); mutex_unlock(&cgroup_mutex); /* Now do the VFS work to create a cgroup */ @@ -1931,6 +2350,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys) (parent != task_cgroup(tsk, subsys->subsys_id))) { /* Aargh, we raced ... */ mutex_unlock(&inode->i_mutex); + put_css_set(cg); deactivate_super(parent->root->sb); /* The cgroup is still accessible in the VFS, but @@ -1954,6 +2374,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys) out_release: mutex_unlock(&inode->i_mutex); + put_css_set(cg); deactivate_super(parent->root->sb); return ret; } diff --git a/kernel/fork.c b/kernel/fork.c index e7c181454dca..fcac38929245 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1301,6 +1301,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, spin_unlock(¤t->sighand->siglock); write_unlock_irq(&tasklist_lock); proc_fork_connector(p); + cgroup_post_fork(p); return p; bad_fork_cleanup_namespaces: |