linux-kernel - [PATCH 4.19 0/3] Backport patches to fix threadgroup_rwsem <-> cpus_read

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Date:   Fri, 3 Mar 2023 04:50:47 +0000
From:   Cai Xinchen <caixinchen1@...wei.com>
To:     <longman@...hat.com>, <lizefan.x@...edance.com>, <tj@...nel.org>,
        <hannes@...xchg.org>, <gregkh@...uxfoundation.org>,
        <sashal@...nel.org>
CC:     <mkoutny@...e.com>, <zhangqiao22@...wei.com>,
        <juri.lelli@...hat.com>, <penguin-kernel@...ove.SAKURA.ne.jp>,
        <stable@...r.kernel.org>, <cgroups@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 4.19 0/3] Backport patches to fix threadgroup_rwsem <-> cpus_read_lock() deadlock

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(-)

-- 
2.17.1