RE: Bad Reference Semantics in PIDs Controller.

From	Aleksa Sarai <cyphar@cyphar.com>
Newsgroups	linux.kernel
Subject	RE: Bad Reference Semantics in PIDs Controller.
Date	2015-08-23 14:30 +0200
Message-ID	<q0Czn-HK-5@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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It turns out that, actually, the can_attach(), cancel_attach() and
attach() code is broken -- we're incrementing a ref on the old_css of
a task in can_attach(). Then we decrement the ref on a *different* css
(because the task has been migrated). This is clearly a bad thing.
Should we make cgroup_migrate() deal with the accounting for us (by
getting it to grab a ref before can_attach() and dropping it after the
attach succeeds or fails?).

-- 
Aleksa Sarai (cyphar)
www.cyphar.com
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RE: Bad Reference Semantics in PIDs Controller. Aleksa Sarai <cyphar@cyphar.com> - 2015-08-23 14:30 +0200
  Re: [PATCH 0/2] cgroup: pids: fix invalid reference semantics Aleksa Sarai <cyphar@cyphar.com> - 2015-08-23 15:20 +0200
  [PATCH 1/2] cgroup: get a ref to source csses when migrating Aleksa Sarai <cyphar@cyphar.com> - 2015-08-23 15:20 +0200
    Re: [PATCH 1/2] cgroup: get a ref to source csses when migrating Tejun Heo <tj@kernel.org> - 2015-08-24 20:50 +0200
      Re: [PATCH 1/2] cgroup: get a ref to source csses when migrating Aleksa Sarai <cyphar@cyphar.com> - 2015-08-25 04:10 +0200
        Re: [PATCH 1/2] cgroup: get a ref to source csses when migrating Tejun Heo <tj@kernel.org> - 2015-08-25 20:20 +0200
  [PATCH 0/2] cgroup: pids: fix invalid reference semantics Aleksa Sarai <cyphar@cyphar.com> - 2015-08-23 15:20 +0200
    [PATCH 2/2] cgroup: pids: fix invalid get/put usage Aleksa Sarai <cyphar@cyphar.com> - 2015-08-23 15:20 +0200
      Re: [PATCH 2/2] cgroup: pids: fix invalid get/put usage Tejun Heo <tj@kernel.org> - 2015-08-24 21:10 +0200

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