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author | Michal Koutný <mkoutny@suse.com> | 2020-01-09 18:05:59 +0300 |
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committer | Tejun Heo <tj@kernel.org> | 2020-01-15 19:04:29 +0300 |
commit | 3bc0bb36fa30e95ca829e9cf480e1ef7f7638333 (patch) | |
tree | cad37dd3b577ac44ac22a5da458812c43ec2106d /tools/cgroup/iocost_monitor.py | |
parent | 75ea91cd3eab8214eb8cd7f61ac23f41884d29ec (diff) | |
download | linux-3bc0bb36fa30e95ca829e9cf480e1ef7f7638333.tar.xz |
cgroup: Prevent double killing of css when enabling threaded cgroup
The test_cgcore_no_internal_process_constraint_on_threads selftest when
running with subsystem controlling noise triggers two warnings:
> [ 597.443115] WARNING: CPU: 1 PID: 28167 at kernel/cgroup/cgroup.c:3131 cgroup_apply_control_enable+0xe0/0x3f0
> [ 597.443413] WARNING: CPU: 1 PID: 28167 at kernel/cgroup/cgroup.c:3177 cgroup_apply_control_disable+0xa6/0x160
Both stem from a call to cgroup_type_write. The first warning was also
triggered by syzkaller.
When we're switching cgroup to threaded mode shortly after a subsystem
was disabled on it, we can see the respective subsystem css dying there.
The warning in cgroup_apply_control_enable is harmless in this case
since we're not adding new subsys anyway.
The warning in cgroup_apply_control_disable indicates an attempt to kill
css of recently disabled subsystem repeatedly.
The commit prevents these situations by making cgroup_type_write wait
for all dying csses to go away before re-applying subtree controls.
When at it, the locations of WARN_ON_ONCE calls are moved so that
warning is triggered only when we are about to misuse the dying css.
Reported-by: syzbot+5493b2a54d31d6aea629@syzkaller.appspotmail.com
Reported-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'tools/cgroup/iocost_monitor.py')
0 files changed, 0 insertions, 0 deletions