diff options
| -rw-r--r-- | kernel/cgroup.c | 62 |
1 files changed, 27 insertions, 35 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index b409df3b2e9d..d71e012e81be 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1762,7 +1762,7 @@ EXPORT_SYMBOL_GPL(cgroup_path); * * 'guarantee' is set if the caller promises that a new css_set for the task * will already exist. If not set, this function might sleep, and can fail with - * -ENOMEM. Otherwise, it can only fail with -ESRCH. + * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked. */ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp, struct task_struct *tsk, bool guarantee) @@ -1800,13 +1800,9 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp, } put_css_set(oldcg); - /* if PF_EXITING is set, the tsk->cgroups pointer is no longer safe. */ + /* @tsk can't exit as its threadgroup is locked */ task_lock(tsk); - if (tsk->flags & PF_EXITING) { - task_unlock(tsk); - put_css_set(newcg); - return -ESRCH; - } + WARN_ON_ONCE(tsk->flags & PF_EXITING); rcu_assign_pointer(tsk->cgroups, newcg); task_unlock(tsk); @@ -1832,8 +1828,8 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp, * @cgrp: the cgroup the task is attaching to * @tsk: the task to be attached * - * Call holding cgroup_mutex. May take task_lock of - * the task 'tsk' during call. + * Call with cgroup_mutex and threadgroup locked. May take task_lock of + * @tsk during call. */ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) { @@ -1842,6 +1838,10 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) struct cgroup *oldcgrp; struct cgroupfs_root *root = cgrp->root; + /* @tsk either already exited or can't exit until the end */ + if (tsk->flags & PF_EXITING) + return -ESRCH; + /* Nothing to do if the task is already in that cgroup */ oldcgrp = task_cgroup_from_root(tsk, root); if (cgrp == oldcgrp) @@ -2062,6 +2062,10 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) tsk = leader; i = 0; do { + /* @tsk either already exited or can't exit until the end */ + if (tsk->flags & PF_EXITING) + continue; + /* as per above, nr_threads may decrease, but not increase. */ BUG_ON(i >= group_size); get_task_struct(tsk); @@ -2116,11 +2120,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) continue; /* get old css_set pointer */ task_lock(tsk); - if (tsk->flags & PF_EXITING) { - /* ignore this task if it's going away */ - task_unlock(tsk); - continue; - } oldcg = tsk->cgroups; get_css_set(oldcg); task_unlock(tsk); @@ -2153,16 +2152,12 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) oldcgrp = task_cgroup_from_root(tsk, root); if (cgrp == oldcgrp) continue; - /* if the thread is PF_EXITING, it can just get skipped. */ retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, true); - if (retval == 0) { - /* attach each task to each subsystem */ - for_each_subsys(root, ss) { - if (ss->attach_task) - ss->attach_task(cgrp, tsk); - } - } else { - BUG_ON(retval != -ESRCH); + BUG_ON(retval); + /* attach each task to each subsystem */ + for_each_subsys(root, ss) { + if (ss->attach_task) + ss->attach_task(cgrp, tsk); } } /* nothing is sensitive to fork() after this point. */ @@ -2215,8 +2210,8 @@ out_free_group_list: /* * Find the task_struct of the task to attach by vpid and pass it along to the - * function to attach either it or all tasks in its threadgroup. Will take - * cgroup_mutex; may take task_lock of task. + * function to attach either it or all tasks in its threadgroup. Will lock + * cgroup_mutex and threadgroup; may take task_lock of task. */ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) { @@ -2243,11 +2238,6 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) * detect it later. */ tsk = tsk->group_leader; - } else if (tsk->flags & PF_EXITING) { - /* optimization for the single-task-only case */ - rcu_read_unlock(); - cgroup_unlock(); - return -ESRCH; } /* * even if we're attaching all tasks in the thread group, we @@ -2271,13 +2261,15 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) get_task_struct(tsk); } - if (threadgroup) { - threadgroup_lock(tsk); + threadgroup_lock(tsk); + + if (threadgroup) ret = cgroup_attach_proc(cgrp, tsk); - threadgroup_unlock(tsk); - } else { + else ret = cgroup_attach_task(cgrp, tsk); - } + + threadgroup_unlock(tsk); + put_task_struct(tsk); cgroup_unlock(); return ret; |