diff options
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index dae50d0d8e4b..4936d8886b4f 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1850,14 +1850,14 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp, struct css_set *newcg; /* - * get old css_set. we need to take task_lock and refcount it, because - * an exiting task can change its css_set to init_css_set and drop its - * old one without taking cgroup_mutex. + * get old css_set. 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. */ - task_lock(tsk); + WARN_ON_ONCE(tsk->flags & PF_EXITING); oldcg = tsk->cgroups; get_css_set(oldcg); - task_unlock(tsk); /* locate or allocate a new css_set for this task. */ if (guarantee) { @@ -1879,9 +1879,7 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp, } put_css_set(oldcg); - /* @tsk can't exit as its threadgroup is locked */ task_lock(tsk); - WARN_ON_ONCE(tsk->flags & PF_EXITING); rcu_assign_pointer(tsk->cgroups, newcg); task_unlock(tsk); @@ -2182,11 +2180,13 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) /* nothing to do if this task is already in the cgroup */ if (tc->cgrp == cgrp) continue; - /* get old css_set pointer */ - task_lock(tc->task); + /* + * get old css_set pointer. threadgroup is locked so this is + * safe against concurrent cgroup_exit() changing this to + * init_css_set. + */ oldcg = tc->task->cgroups; get_css_set(oldcg); - task_unlock(tc->task); /* see if the new one for us is already in the list? */ if (css_set_check_fetched(cgrp, tc->task, oldcg, &newcg_list)) { /* was already there, nothing to do. */ |