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authorTejun Heo <tj@kernel.org>2019-05-31 20:38:58 +0300
committerTejun Heo <tj@kernel.org>2019-05-31 20:38:58 +0300
commitc03cd7738a83b13739f00546166969342c8ff014 (patch)
tree6ac8b0e1001dbfc3c7eb8df089bc500aeeab9a24 /kernel
parentb636fd38dc40113f853337a7d2a6885ad23b8811 (diff)
downloadlinux-c03cd7738a83b13739f00546166969342c8ff014.tar.xz
cgroup: Include dying leaders with live threads in PROCS iterations
CSS_TASK_ITER_PROCS currently iterates live group leaders; however, this means that a process with dying leader and live threads will be skipped. IOW, cgroup.procs might be empty while cgroup.threads isn't, which is confusing to say the least. Fix it by making cset track dying tasks and include dying leaders with live threads in PROCS iteration. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-tested-by: Topi Miettinen <toiwoton@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup/cgroup.c44
1 files changed, 37 insertions, 7 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 035aee466bbf..a7df319c2e9a 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -739,6 +739,7 @@ struct css_set init_css_set = {
.dom_cset = &init_css_set,
.tasks = LIST_HEAD_INIT(init_css_set.tasks),
.mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
+ .dying_tasks = LIST_HEAD_INIT(init_css_set.dying_tasks),
.task_iters = LIST_HEAD_INIT(init_css_set.task_iters),
.threaded_csets = LIST_HEAD_INIT(init_css_set.threaded_csets),
.cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
@@ -1213,6 +1214,7 @@ static struct css_set *find_css_set(struct css_set *old_cset,
cset->dom_cset = cset;
INIT_LIST_HEAD(&cset->tasks);
INIT_LIST_HEAD(&cset->mg_tasks);
+ INIT_LIST_HEAD(&cset->dying_tasks);
INIT_LIST_HEAD(&cset->task_iters);
INIT_LIST_HEAD(&cset->threaded_csets);
INIT_HLIST_NODE(&cset->hlist);
@@ -4399,15 +4401,18 @@ static void css_task_iter_advance_css_set(struct css_task_iter *it)
it->task_pos = NULL;
return;
}
- } while (!css_set_populated(cset));
+ } while (!css_set_populated(cset) && !list_empty(&cset->dying_tasks));
if (!list_empty(&cset->tasks))
it->task_pos = cset->tasks.next;
- else
+ else if (!list_empty(&cset->mg_tasks))
it->task_pos = cset->mg_tasks.next;
+ else
+ it->task_pos = cset->dying_tasks.next;
it->tasks_head = &cset->tasks;
it->mg_tasks_head = &cset->mg_tasks;
+ it->dying_tasks_head = &cset->dying_tasks;
/*
* We don't keep css_sets locked across iteration steps and thus
@@ -4446,6 +4451,8 @@ static void css_task_iter_skip(struct css_task_iter *it,
static void css_task_iter_advance(struct css_task_iter *it)
{
+ struct task_struct *task;
+
lockdep_assert_held(&css_set_lock);
repeat:
if (it->task_pos) {
@@ -4462,17 +4469,32 @@ repeat:
if (it->task_pos == it->tasks_head)
it->task_pos = it->mg_tasks_head->next;
if (it->task_pos == it->mg_tasks_head)
+ it->task_pos = it->dying_tasks_head->next;
+ if (it->task_pos == it->dying_tasks_head)
css_task_iter_advance_css_set(it);
} else {
/* called from start, proceed to the first cset */
css_task_iter_advance_css_set(it);
}
- /* if PROCS, skip over tasks which aren't group leaders */
- if ((it->flags & CSS_TASK_ITER_PROCS) && it->task_pos &&
- !thread_group_leader(list_entry(it->task_pos, struct task_struct,
- cg_list)))
- goto repeat;
+ if (!it->task_pos)
+ return;
+
+ task = list_entry(it->task_pos, struct task_struct, cg_list);
+
+ if (it->flags & CSS_TASK_ITER_PROCS) {
+ /* if PROCS, skip over tasks which aren't group leaders */
+ if (!thread_group_leader(task))
+ goto repeat;
+
+ /* and dying leaders w/o live member threads */
+ if (!atomic_read(&task->signal->live))
+ goto repeat;
+ } else {
+ /* skip all dying ones */
+ if (task->flags & PF_EXITING)
+ goto repeat;
+ }
}
/**
@@ -6009,6 +6031,7 @@ void cgroup_exit(struct task_struct *tsk)
if (!list_empty(&tsk->cg_list)) {
spin_lock_irq(&css_set_lock);
css_set_move_task(tsk, cset, NULL, false);
+ list_add_tail(&tsk->cg_list, &cset->dying_tasks);
cset->nr_tasks--;
WARN_ON_ONCE(cgroup_task_frozen(tsk));
@@ -6034,6 +6057,13 @@ void cgroup_release(struct task_struct *task)
do_each_subsys_mask(ss, ssid, have_release_callback) {
ss->release(task);
} while_each_subsys_mask();
+
+ if (use_task_css_set_links) {
+ spin_lock_irq(&css_set_lock);
+ css_set_skip_task_iters(task_css_set(task), task);
+ list_del_init(&task->cg_list);
+ spin_unlock_irq(&css_set_lock);
+ }
}
void cgroup_free(struct task_struct *task)