From: Zhang Qiao zhangqiao22@huawei.com
The backport commit 4eec5fe1c680a ("cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug") looks suspicious since it comes before commit d74b27d63a8b ("cgroup/cpuset: Change cpuset_rwsem and hotplug lock order") v5.4-rc1~176^2~30 when the locking order was: cpuset lock, cpus lock.
Fix it with the correct locking order and reduce the cpus locking range because only set_cpus_allowed_ptr() needs the protection of cpus lock.
Fixes: 4eec5fe1c680a ("cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug") Reported-by: Michal Koutný mkoutny@suse.com Signed-off-by: Zhang Qiao zhangqiao22@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/cgroup/cpuset.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1528,9 +1528,13 @@ static void cpuset_attach(struct cgroup_ cgroup_taskset_first(tset, &css); cs = css_cs(css);
- cpus_read_lock(); mutex_lock(&cpuset_mutex);
+ /* + * It should hold cpus lock because a cpu offline event can + * cause set_cpus_allowed_ptr() failed. + */ + get_online_cpus(); /* prepare for attach */ if (cs == &top_cpuset) cpumask_copy(cpus_attach, cpu_possible_mask); @@ -1549,6 +1553,7 @@ static void cpuset_attach(struct cgroup_ cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to); cpuset_update_task_spread_flag(cs, task); } + put_online_cpus();
/* * Change mm for all threadgroup leaders. This is expensive and may @@ -1584,7 +1589,6 @@ static void cpuset_attach(struct cgroup_ wake_up(&cpuset_attach_wq);
mutex_unlock(&cpuset_mutex); - cpus_read_unlock(); }
/* The various types of files and directories in a cpuset file system */