From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cai Xinchen Subject: [PATCH v2 4.19 0/3] Backport patches to fix threadgroup_rwsem <-> cpus_read_lock() deadlock Date: Mon, 20 Mar 2023 01:15:04 +0000 Message-ID: <20230320011507.129441-1-caixinchen1@huawei.com> Mime-Version: 1.0 Return-path: List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: longman@redhat.com, lizefan.x@bytedance.com, tj@kernel.org, hannes@cmpxchg.org, gregkh@linuxfoundation.org, sashal@kernel.org Cc: mkoutny@suse.com, zhangqiao22@huawei.com, juri.lelli@redhat.com, penguin-kernel@I-love.SAKURA.ne.jp, stable@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org I am very sorry. My gcc version is 7.5 and it does not report error. 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") Changes in v2: * Add #include in kernel/cgroup/cgroup.c to avoid some compile error. * Exchange get_online_cpus() location in cpuset_attach to keep cpu_hotplug_lock->cpuset_mutex order, although it will be remove by ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock") 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 | 50 +++++++++++++++++++++++++++++++++++---- kernel/cgroup/cpuset.c | 25 ++++++++++++-------- 4 files changed, 67 insertions(+), 19 deletions(-) -- 2.17.1