On Fri, Mar 03, 2023 at 04:50:47AM +0000, Cai Xinchen wrote:
> We have a deadlock problem which can be solved by commit 4f7e7236435ca
> ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock").
> However, it makes lock order of cpus_read_lock and cpuset_mutex
> wrong in v4.19. The call sequence is as follows:
> cgroup_procs_write()
> cgroup_procs_write_start()
> get_online_cpus(); // cpus_read_lock()
> percpu_down_write(&cgroup_threadgroup_rwsem)
> cgroup_attach_task
> cgroup_migrate
> cgroup_migrate_execute
> ss->attach (cpust_attach)
> mutex_lock(&cpuset_mutex)
>
> it seems hard to make cpus_read_lock is locked before
> cgroup_threadgroup_rwsem and cpuset_mutex is locked before
> cpus_read_lock unless backport the commit d74b27d63a8beb
> ("cgroup/cpuset: Change cpuset_rwsem and hotplug lock order")
>
> Juri Lelli (1):
> cgroup/cpuset: Change cpuset_rwsem and hotplug lock order
>
> Tejun Heo (1):
> cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock
>
> Tetsuo Handa (1):
> cgroup: Add missing cpus_read_lock() to cgroup_attach_task_all()
>
> include/linux/cpuset.h | 8 +++----
> kernel/cgroup/cgroup-v1.c | 3 +++
> kernel/cgroup/cgroup.c | 49 +++++++++++++++++++++++++++++++++++----
> kernel/cgroup/cpuset.c | 25 ++++++++++++--------
> 4 files changed, 66 insertions(+), 19 deletions(-)
This series breaks the build on many architectures, so I will now have
to go drop them from the 4.19.y queue. Please fix up and resubmit if
you wish to have them applied in the future.
thanks,
greg k-h