Messages in this thread | | | Date | Wed, 17 Aug 2022 06:20:08 +1000 | Subject | Re: [PATCH cgroup/for-6.0-fixes] cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock | From | Imran Khan <> |
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Hello Tejun,
On 16/8/22 9:27 am, Tejun Heo wrote: > Bringing up a CPU may involve creating new 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> > --- > Hello, sorry about the delay. > > So, the previous patch + the revert isn't quite correct because we sometimes > elide both cpus_read_lock() and threadgroup_rwsem together and > cpuset_attach() woudl end up running without CPU hotplug enabled. Can you > please test whether this patch fixes the problem? >
This fixes the issue seen in my setup. As my setup is 5.4 based I used cgroup_attach_lock/unlock(true) in the backport version of your patch.
Feel free to add my
Reviewed-and-tested-by: Imran Khan <imran.f.khan@oracle.com>
Thanks, -- Imran
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