diff options
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 103 |
1 files changed, 48 insertions, 55 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 506f6da67ad1..2469699408bd 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -173,7 +173,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp); static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], bool is_add); static void cgroup_pidlist_destroy_all(struct cgroup *cgrp); -static void cgroup_enable_task_cg_lists(void); /** * cgroup_css - obtain a cgroup's css for the specified subsystem @@ -370,14 +369,6 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) return key; } -/* - * We don't maintain the lists running through each css_set to its task - * until after the first call to css_task_iter_start(). This reduces the - * fork()/exit() overhead for people who have cgroups compiled into their - * kernel but not actually in use. - */ -static bool use_task_css_set_links __read_mostly; - static void __put_css_set(struct css_set *cset, int taskexit) { struct cgrp_cset_link *link, *tmp_link; @@ -1307,6 +1298,54 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data) return ret; } +/* + * To reduce the fork() overhead for systems that are not actually using + * their cgroups capability, we don't maintain the lists running through + * each css_set to its tasks until we see the list actually used - in other + * words after the first mount. + */ +static bool use_task_css_set_links __read_mostly; + +static void cgroup_enable_task_cg_lists(void) +{ + struct task_struct *p, *g; + + write_lock(&css_set_lock); + + if (use_task_css_set_links) + goto out_unlock; + + use_task_css_set_links = true; + + /* + * We need tasklist_lock because RCU is not safe against + * while_each_thread(). Besides, a forking task that has passed + * cgroup_post_fork() without seeing use_task_css_set_links = 1 + * is not guaranteed to have its child immediately visible in the + * tasklist if we walk through it with RCU. + */ + read_lock(&tasklist_lock); + do_each_thread(g, p) { + task_lock(p); + + WARN_ON_ONCE(!list_empty(&p->cg_list) || + task_css_set(p) != &init_css_set); + + /* + * We should check if the process is exiting, otherwise + * it will race with cgroup_exit() in that the list + * entry won't be deleted though the process has exited. + */ + if (!(p->flags & PF_EXITING)) + list_add(&p->cg_list, &task_css_set(p)->tasks); + + task_unlock(p); + } while_each_thread(g, p); + read_unlock(&tasklist_lock); +out_unlock: + write_unlock(&css_set_lock); +} + static void init_cgroup_housekeeping(struct cgroup *cgrp) { atomic_set(&cgrp->refcnt, 1); @@ -2364,52 +2403,6 @@ int cgroup_task_count(const struct cgroup *cgrp) return count; } -/* - * To reduce the fork() overhead for systems that are not actually using - * their cgroups capability, we don't maintain the lists running through - * each css_set to its tasks until we see the list actually used - in other - * words after the first mount. - */ -static void cgroup_enable_task_cg_lists(void) -{ - struct task_struct *p, *g; - - write_lock(&css_set_lock); - - if (use_task_css_set_links) - goto out_unlock; - - use_task_css_set_links = true; - - /* - * We need tasklist_lock because RCU is not safe against - * while_each_thread(). Besides, a forking task that has passed - * cgroup_post_fork() without seeing use_task_css_set_links = 1 - * is not guaranteed to have its child immediately visible in the - * tasklist if we walk through it with RCU. - */ - read_lock(&tasklist_lock); - do_each_thread(g, p) { - task_lock(p); - - WARN_ON_ONCE(!list_empty(&p->cg_list) || - task_css_set(p) != &init_css_set); - - /* - * We should check if the process is exiting, otherwise - * it will race with cgroup_exit() in that the list - * entry won't be deleted though the process has exited. - */ - if (!(p->flags & PF_EXITING)) - list_add(&p->cg_list, &task_css_set(p)->tasks); - - task_unlock(p); - } while_each_thread(g, p); - read_unlock(&tasklist_lock); -out_unlock: - write_unlock(&css_set_lock); -} - /** * css_next_child - find the next child of a given css * @pos_css: the current position (%NULL to initiate traversal) |
