linux-kernel - [PATCH 0/3] CGroups: Hierarchy locking/refcount changes

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Message-Id: <20081216113055.713856000@menage.corp.google.com>
Date:	Tue, 16 Dec 2008 03:30:55 -0800
From:	menage@...gle.com
To:	akpm@...ux-foundation.org, kamezawa.hiroyu@...fujitsu.com,
	lizf@...fujitsu.com
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 0/3] CGroups: Hierarchy locking/refcount changes

These patches introduce new locking/refcount support for cgroups to
reduce the need for subsystems to call cgroup_lock(). This will
ultimately allow the atomicity of cgroup_rmdir() (which was removed
recently) to be restored.

These three patches give:

1/3 - introduce a per-subsystem hierarchy_mutex which a subsystem can
     use to prevent changes to its own cgroup tree

2/3 - use hierarchy_mutex in place of calling cgroup_lock() in the
     memory controller

3/3 - introduce a css_tryget() function similar to the one recently
      proposed by Kamezawa, but avoiding spurious refcount failures in
      the event of a race between a css_tryget() and an unsuccessful
      cgroup_rmdir()

Future patches will likely involve:

- using hierarchy mutex in place of cgroup_lock() in more subsystems
 where appropriate

- restoring the atomicity of cgroup_rmdir() with respect to cgroup_create()

Signed-off-by: Paul Menage <menage@...gle.com>

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