It's not allowed to clear masks of a cpuset if there're tasks in it,
but it's broken:
# mkdir /cgroup/sub
# echo 0 > /cgroup/sub/cpuset.cpus
# echo 0 > /cgroup/sub/cpuset.mems
# echo $$ > /cgroup/sub/tasks
# echo > /cgroup/sub/cpuset.cpus
(should fail)
This bug was introduced by commit 88fa523bff295f1d60244a54833480b02f775152
("cpuset: allow to move tasks to empty cpusets").
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
---
kernel/cpuset.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 0b5b9a3..70ab3fd 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -425,6 +425,8 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial)
struct cgroup_subsys_state *css;
struct cpuset *c, *par;
int ret;
+ bool make_cpus_empty;
+ bool make_mems_empty;
rcu_read_lock();
@@ -464,12 +466,15 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial)
/*
* Cpusets with tasks - existing or newly being attached - can't
- * have empty cpus_allowed or mems_allowed.
+ * be changed to have empty cpus_allowed or mems_allowed.
*/
ret = -ENOSPC;
+ make_cpus_empty = !cpumask_empty(cur->cpus_allowed) &&
+ cpumask_empty(trial->cpus_allowed);
+ make_mems_empty = !nodes_empty(cur->mems_allowed) &&
+ nodes_empty(trial->mems_allowed);
if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress) &&
- (cpumask_empty(trial->cpus_allowed) &&
- nodes_empty(trial->mems_allowed)))
+ (make_cpus_empty || make_mems_empty))
goto out;
ret = 0;
--
1.8.0.2
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