> On Wed, Aug 11, 2010 at 01:46:04AM -0400, Ben Blum wrote:
> > On Fri, Jul 30, 2010 at 07:56:49PM -0400, Ben Blum wrote:
> > > 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(-)
> >
> > Here's an updated patchset. I've added an extra patch to implement the
> > callback scheme Paul suggested (note how there are twice as many deleted
> > lines of code as before :) ), and also moved the up_read/down_read calls
> > to static inline functions in sched.h near the other threadgroup-related
> > calls.
>
> One more go at this. I've refreshed the patches for some conflicts in
> cgroup_freezer.c, by adding an extra argument to the per_thread() call,
> "need_rcu", which makes the function take rcu_read_lock even around the
> single-task case (like freezer now requires). So no semantics have been
> changed.
>
> I also poked around at some attach() calls which also iterate over the
> threadgroup (blkiocg_attach, cpuset_attach, cpu_cgroup_attach). I was
> borderline about making another function, cgroup_attach_per_thread(),
> but decided against.
>
> There is a big issue in cpuset_attach, as explained in this email:
>
http://www.spinics.net/lists/linux-containers/msg22223.html
> but the actual code/diffs for this patchset are independent of that
> getting fixed, so I'm putting this up for consideration now.
>
> -- Ben
