diff options
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 77 |
1 files changed, 20 insertions, 57 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 980b1f52f39f..77578a169b8c 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -46,6 +46,7 @@ #include <linux/slab.h> #include <linux/spinlock.h> #include <linux/rwsem.h> +#include <linux/percpu-rwsem.h> #include <linux/string.h> #include <linux/sort.h> #include <linux/kmod.h> @@ -103,6 +104,8 @@ static DEFINE_SPINLOCK(cgroup_idr_lock); */ static DEFINE_SPINLOCK(release_agent_path_lock); +struct percpu_rw_semaphore cgroup_threadgroup_rwsem; + #define cgroup_assert_mutex_or_rcu_locked() \ rcu_lockdep_assert(rcu_read_lock_held() || \ lockdep_is_held(&cgroup_mutex), \ @@ -848,48 +851,6 @@ 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; @@ -2095,9 +2056,9 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, lockdep_assert_held(&css_set_rwsem); /* - * We are synchronized through threadgroup_lock() against PF_EXITING - * setting such that we can't race against cgroup_exit() changing the - * css_set to init_css_set and dropping the old one. + * We are synchronized through cgroup_threadgroup_rwsem against + * PF_EXITING setting such that we can't race against cgroup_exit() + * changing the css_set to init_css_set and dropping the old one. */ WARN_ON_ONCE(tsk->flags & PF_EXITING); old_cset = task_css_set(tsk); @@ -2154,10 +2115,11 @@ static void cgroup_migrate_finish(struct list_head *preloaded_csets) * @src_cset and add it to @preloaded_csets, which should later be cleaned * up by cgroup_migrate_finish(). * - * This function may be called without holding threadgroup_lock even if the - * target is a process. Threads may be created and destroyed but as long - * as cgroup_mutex is not dropped, no new css_set can be put into play and - * the preloaded css_sets are guaranteed to cover all migrations. + * This function may be called without holding cgroup_threadgroup_rwsem + * even if the target is a process. Threads may be created and destroyed + * but as long as cgroup_mutex is not dropped, no new css_set can be put + * into play and the preloaded css_sets are guaranteed to cover all + * migrations. */ static void cgroup_migrate_add_src(struct css_set *src_cset, struct cgroup *dst_cgrp, @@ -2260,7 +2222,7 @@ err: * @threadgroup: whether @leader points to the whole process or a single task * * Migrate a process or task denoted by @leader to @cgrp. If migrating a - * process, the caller must be holding threadgroup_lock of @leader. The + * process, the caller must be holding cgroup_threadgroup_rwsem. The * caller is also responsible for invoking cgroup_migrate_add_src() and * cgroup_migrate_prepare_dst() on the targets before invoking this * function and following up with cgroup_migrate_finish(). @@ -2388,7 +2350,7 @@ out_release_tset: * @leader: the task or the leader of the threadgroup to be attached * @threadgroup: attach the whole threadgroup? * - * Call holding cgroup_mutex and threadgroup_lock of @leader. + * Call holding cgroup_mutex and cgroup_threadgroup_rwsem. */ static int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader, bool threadgroup) @@ -2481,7 +2443,7 @@ retry_find_task: get_task_struct(tsk); rcu_read_unlock(); - threadgroup_lock(tsk); + percpu_down_write(&cgroup_threadgroup_rwsem); if (threadgroup) { if (!thread_group_leader(tsk)) { /* @@ -2491,7 +2453,7 @@ retry_find_task: * try again; this is * "double-double-toil-and-trouble-check locking". */ - threadgroup_unlock(tsk); + percpu_up_write(&cgroup_threadgroup_rwsem); put_task_struct(tsk); goto retry_find_task; } @@ -2499,7 +2461,7 @@ retry_find_task: ret = cgroup_attach_task(cgrp, tsk, threadgroup); - threadgroup_unlock(tsk); + percpu_up_write(&cgroup_threadgroup_rwsem); put_task_struct(tsk); out_unlock_cgroup: @@ -2704,17 +2666,17 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp) goto out_finish; last_task = task; - threadgroup_lock(task); + percpu_down_write(&cgroup_threadgroup_rwsem); /* raced against de_thread() from another thread? */ if (!thread_group_leader(task)) { - threadgroup_unlock(task); + percpu_up_write(&cgroup_threadgroup_rwsem); put_task_struct(task); continue; } ret = cgroup_migrate(src_cset->dfl_cgrp, task, true); - threadgroup_unlock(task); + percpu_up_write(&cgroup_threadgroup_rwsem); put_task_struct(task); if (WARN(ret, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret)) @@ -5032,6 +4994,7 @@ int __init cgroup_init(void) unsigned long key; int ssid, err; + BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem)); BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files)); BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files)); |