Messages in this thread |  | | Date | Tue, 8 Dec 2015 14:58:51 +0000 | | From | Andy Whitcroft <> | | Subject | cgroup pids controller -- WARN_ON_ONCE triggering |
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The commit below attempts to fix up pid controller charging:
commit afcf6c8b75444382e0f9996157207ebae34a8848 Author: Tejun Heo <tj@kernel.org> 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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