cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock

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Bringing up a CPU may involve creating and destroying tasks which requires
read-locking threadgroup_rwsem, so threadgroup_rwsem nests inside
cpus_read_lock(). However, cpuset's ->attach(), which may be called with
thredagroup_rwsem write-locked, also wants to disable CPU hotplug and
acquires cpus_read_lock(), leading to a deadlock.

Fix it by guaranteeing that ->attach() is always called with CPU hotplug
disabled and removing cpus_read_lock() call from cpuset_attach().

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-and-tested-by: Imran Khan <imran.f.khan@oracle.com>
Reported-and-tested-by: Xuewen Yan <xuewen.yan@unisoc.com>
Fixes: 05c7b7a92c ("cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug")
Cc: stable@vger.kernel.org # v5.17+

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This commit is contained in:

Tejun Heo 2022-08-15 13:27:38 -10:00

parent d7ae5818c3

commit 4f7e723643

2 changed files with 55 additions and 25 deletions

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77

kernel/cgroup/cgroup.c

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3

kernel/cgroup/cpuset.c

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