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    Subject[PATCH v4 0/2] cgroups: implement moving a threadgroup's threads atomically with cgroup.procs
    This patch series is a revision of http://lkml.org/lkml/2010/6/25/11 .

    This patch series implements a write function for the 'cgroup.procs'
    per-cgroup file, which enables atomic movement of multithreaded
    applications between cgroups. Writing the thread-ID of any thread in a
    threadgroup to a cgroup's procs file causes all threads in the group to
    be moved to that cgroup safely with respect to threads forking/exiting.
    (Possible usage scenario: If running a multithreaded build system that
    sucks up system resources, this lets you restrict it all at once into a
    new cgroup to keep it under control.)

    Example: Suppose pid 31337 clones new threads 31338 and 31339.

    # cat /dev/cgroup/tasks
    ...
    31337
    31338
    31339
    # mkdir /dev/cgroup/foo
    # echo 31337 > /dev/cgroup/foo/cgroup.procs
    # cat /dev/cgroup/foo/tasks
    31337
    31338
    31339

    A new lock, called threadgroup_fork_lock and living in signal_struct, is
    introduced to ensure atomicity when moving threads between cgroups. It's
    taken for writing during the operation, and taking for reading in fork()
    around the calls to cgroup_fork() and cgroup_post_fork(). I put calls to
    down_read/up_read directly in copy_process(), since new inline functions
    seemed like overkill.

    -- Ben

    ---
    Documentation/cgroups/cgroups.txt | 13 -
    include/linux/init_task.h | 9
    include/linux/sched.h | 10
    kernel/cgroup.c | 426 +++++++++++++++++++++++++++++++++-----
    kernel/cgroup_freezer.c | 4
    kernel/cpuset.c | 4
    kernel/fork.c | 16 +
    kernel/ns_cgroup.c | 4
    kernel/sched.c | 4
    9 files changed, 440 insertions(+), 50 deletions(-)


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