From 96b9c592def5d7203bdad1337d9c92a2183de5cb Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Fri, 26 Apr 2019 10:59:45 -0700 Subject: cgroup: get rid of cgroup_freezer_frozen_exit() A task should never enter the exit path with the task->frozen bit set. Any frozen task must enter the signal handling loop and the only way to escape is through cgroup_leave_frozen(true), which unconditionally drops the task->frozen bit. So it means that cgroyp_freezer_frozen_exit() has zero chances to be called and has to be removed. Let's put a WARN_ON_ONCE() instead of the cgroup_freezer_frozen_exit() call to catch any potential leak of the task's frozen bit. Suggested-by: Oleg Nesterov Signed-off-by: Roman Gushchin Signed-off-by: Tejun Heo --- kernel/cgroup/cgroup.c | 5 ++--- kernel/cgroup/freezer.c | 10 ---------- 2 files changed, 2 insertions(+), 13 deletions(-) (limited to 'kernel/cgroup') diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 4fe9f7f1a3fa..327f37c9fdfa 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5926,9 +5926,8 @@ void cgroup_exit(struct task_struct *tsk) css_set_move_task(tsk, cset, NULL, false); cset->nr_tasks--; - if (unlikely(cgroup_task_frozen(tsk))) - cgroup_freezer_frozen_exit(tsk); - else if (unlikely(cgroup_task_freeze(tsk))) + WARN_ON_ONCE(cgroup_task_frozen(tsk)); + if (unlikely(cgroup_task_freeze(tsk))) cgroup_update_frozen(task_dfl_cgroup(tsk)); spin_unlock_irq(&css_set_lock); diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c index c321e768f8d3..8cf010680678 100644 --- a/kernel/cgroup/freezer.c +++ b/kernel/cgroup/freezer.c @@ -248,16 +248,6 @@ void cgroup_freezer_migrate_task(struct task_struct *task, cgroup_freeze_task(task, test_bit(CGRP_FREEZE, &dst->flags)); } -void cgroup_freezer_frozen_exit(struct task_struct *task) -{ - struct cgroup *cgrp = task_dfl_cgroup(task); - - lockdep_assert_held(&css_set_lock); - - cgroup_dec_frozen_cnt(cgrp); - cgroup_update_frozen(cgrp); -} - void cgroup_freeze(struct cgroup *cgrp, bool freeze) { struct cgroup_subsys_state *css; -- cgit v1.2.3-55-g7522