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@xxxxxxxxxx> > --- > 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@xxxxxxxxxx> Thanks, -- Imran
