On Wed 17-08-11 21:49:27, Johannes Weiner wrote:

Commit d1a05b6 'memcg: do not try to drain per-cpu caches without
pages' added a drain_local_stock() call to a preemptible section.

The draining task looks up the cpu-local stock twice to set the
draining-flag, then to drain the stock and clear the flag again.  If
the task is migrated to a different CPU in between, noone will clear
the flag on the first stock and it will be forever undrainable.  Its
charge can not be recovered and the cgroup can not be deleted anymore.

Properly pin the task to the executing CPU while draining stocks.

Signed-off-by: Johannes Weiner <redacted>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com
Cc: Michal Hocko <redacted>

My fault, I didn't realize that drain_local_stock needs preemption
disabled. Sorry about that and good work, Johannes. 

Acked-by: Michal Hocko <redacted>
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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