[Devel] Re: [RFC][PATCH 2/3] CGroups: Use hierarchy_mutex in memory controller

[Paul Menage]

On Wed, Dec 10, 2008 at 4:49 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu at jp.fujitsu.com> wrote:
>
>        an operation like rmdir() in somewhere.
>                hierarchy_lock for A (acquired)
>                hierarchy_lock for B (waiting)
>
>        in subsys A.
>                mmap_sem (acquired)
>                hierarchy_lock for A (waiting)
>        in subsys B.
>                hierarchy_lock for B (aquired)
>                mmap_sem             (waiting)
>

That's a valid deadlock - you'd need to require the mmap_sem nests
either inside all hierarchy_mutexes or else outside all of them.

Paul
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