diff options
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 95 |
1 files changed, 75 insertions, 20 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 3abce1e0f910..141458d06e57 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -175,12 +175,13 @@ static DEFINE_IDR(cgroup_hierarchy_idr); */ static u64 css_serial_nr_next = 1; -/* This flag indicates whether tasks in the fork and exit paths should - * check for fork/exit handlers to call. This avoids us having to do - * extra work in the fork/exit path if none of the subsystems need to - * be called. +/* + * These bitmask flags indicate whether tasks in the fork and exit paths have + * fork/exit handlers to call. This avoids us having to do extra work in the + * fork/exit path to check which subsystems have fork/exit callbacks. */ -static int need_forkexit_callback __read_mostly; +static unsigned long have_fork_callback __read_mostly; +static unsigned long have_exit_callback __read_mostly; static struct cftype cgroup_dfl_base_files[]; static struct cftype cgroup_legacy_base_files[]; @@ -409,6 +410,24 @@ static int notify_on_release(const struct cgroup *cgrp) for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \ (((ss) = cgroup_subsys[ssid]) || true); (ssid)++) +/** + * for_each_subsys_which - filter for_each_subsys with a bitmask + * @ss: the iteration cursor + * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end + * @ss_maskp: a pointer to the bitmask + * + * The block will only run for cases where the ssid-th bit (1 << ssid) of + * mask is set to 1. + */ +#define for_each_subsys_which(ss, ssid, ss_maskp) \ + if (!CGROUP_SUBSYS_COUNT) /* to avoid spurious gcc warning */ \ + ; \ + else \ + for_each_set_bit(ssid, ss_maskp, CGROUP_SUBSYS_COUNT) \ + if (((ss) = cgroup_subsys[ssid]) && false) \ + break; \ + else + /* iterate across the hierarchies */ #define for_each_root(root) \ list_for_each_entry((root), &cgroup_roots, root_list) @@ -848,6 +867,48 @@ static struct css_set *find_css_set(struct css_set *old_cset, return cset; } +void cgroup_threadgroup_change_begin(struct task_struct *tsk) +{ + down_read(&tsk->signal->group_rwsem); +} + +void cgroup_threadgroup_change_end(struct task_struct *tsk) +{ + up_read(&tsk->signal->group_rwsem); +} + +/** + * threadgroup_lock - lock threadgroup + * @tsk: member task of the threadgroup to lock + * + * Lock the threadgroup @tsk belongs to. No new task is allowed to enter + * and member tasks aren't allowed to exit (as indicated by PF_EXITING) or + * change ->group_leader/pid. This is useful for cases where the threadgroup + * needs to stay stable across blockable operations. + * + * fork and exit explicitly call threadgroup_change_{begin|end}() for + * synchronization. While held, no new task will be added to threadgroup + * and no existing live task will have its PF_EXITING set. + * + * de_thread() does threadgroup_change_{begin|end}() when a non-leader + * sub-thread becomes a new leader. + */ +static void threadgroup_lock(struct task_struct *tsk) +{ + down_write(&tsk->signal->group_rwsem); +} + +/** + * threadgroup_unlock - unlock threadgroup + * @tsk: member task of the threadgroup to unlock + * + * Reverse threadgroup_lock(). + */ +static inline void threadgroup_unlock(struct task_struct *tsk) +{ + up_write(&tsk->signal->group_rwsem); +} + static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root) { struct cgroup *root_cgrp = kf_root->kn->priv; @@ -4941,7 +5002,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early) * init_css_set is in the subsystem's root cgroup. */ init_css_set.subsys[ss->id] = css; - need_forkexit_callback |= ss->fork || ss->exit; + have_fork_callback |= (bool)ss->fork << ss->id; + have_exit_callback |= (bool)ss->exit << ss->id; /* At system boot, before all subsystems have been * registered, no tasks have been forked, so we don't @@ -5251,11 +5313,8 @@ void cgroup_post_fork(struct task_struct *child) * css_set; otherwise, @child might change state between ->fork() * and addition to css_set. */ - if (need_forkexit_callback) { - for_each_subsys(ss, i) - if (ss->fork) - ss->fork(child); - } + for_each_subsys_which(ss, i, &have_fork_callback) + ss->fork(child); } /** @@ -5299,16 +5358,12 @@ void cgroup_exit(struct task_struct *tsk) cset = task_css_set(tsk); RCU_INIT_POINTER(tsk->cgroups, &init_css_set); - if (need_forkexit_callback) { - /* see cgroup_post_fork() for details */ - for_each_subsys(ss, i) { - if (ss->exit) { - struct cgroup_subsys_state *old_css = cset->subsys[i]; - struct cgroup_subsys_state *css = task_css(tsk, i); + /* see cgroup_post_fork() for details */ + for_each_subsys_which(ss, i, &have_exit_callback) { + struct cgroup_subsys_state *old_css = cset->subsys[i]; + struct cgroup_subsys_state *css = task_css(tsk, i); - ss->exit(css, old_css, tsk); - } - } + ss->exit(css, old_css, tsk); } if (put_cset) |