The commit below attempts to fix up pid controller charging:
commit afcf6c8b75444382e0f9996157207ebae34a8848
Author: Tejun Heo <tj@xxxxxxxxxx>
Date: Thu Oct 15 16:41:53 2015 -0400
cgroup: add cgroup_subsys->free() method and use it to fix pids controller
Since this change we are seeing system hangs in early boot on multiple
architecures. We have a console log on ppc64el [1] which fingers
pids_cancel(). Manual debugging on amd64 VMs seems to indicate that we
are now tripping the WARN_ON_ONCE() below:
static void pids_cancel(struct pids_cgroup *pids, int num)
{
/*
* A negative count (or overflow for that matter) is invalid,
* and indicates a bug in the `pids` controller proper.
*/
WARN_ON_ONCE(atomic64_add_negative(-num, &pids->counter));
}
Converting this to a printk I was able to obtain confirmation that we are
indeed seeing this go negative in some cases.
Reverting the above commit seems to resolve the early boot issues in
my testing.
-apw
[1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1523586
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