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SubjectRe: [PATCHSET cgroup] extend threadgroup locking
Tejun Heo wrote:
> Hello,
>
> cgroup currently only blocks new threads from joining the target
> threadgroup during migration, and on-going migration could race
> against exec and exit leading to interesting problems - the symmetry
> between various attach methods, task exiting during method execution,
> ->exit() racing against attach methods, migrating task switching basic
> properties during exec and so on.
>
> This patchset extends threadgroup locking such that it covers all
> operations which can alter the threadgroup - fork, exit and exec, and
> update cgroup to take advantage of it. rwsem read ops are added to
> exit path but exec is excluded by grabbing the existing
> cred_guard_mutex from threadgroup locking helper.
>
> This makes threadgroup locking complete and resolves cgroup issues
> stemming from the target taskset being unstable.
>
> This patchset is on top of the current pm-freezer + "freezer: fixes &
> simplifications" patchset and contains the following four patches.
> Patch list and diffstat follow.
>
> Thanks.
>
> [PATCH 1/4] cgroup: change locking order in attach_task_by_pid()
> [PATCH 2/4] threadgroup: rename signal->threadgroup_fork_lock to
> [PATCH 3/4] threadgroup: extend threadgroup_lock() to cover exit and
> [PATCH 4/4] cgroup: always lock threadgroup during migration
>

I've read through the whole patchset, and it looks good to me.

Acked-by: Li Zefan <lizf@cn.fujitsu.com>

> include/linux/init_task.h | 9 ++----
> include/linux/sched.h | 58 ++++++++++++++++++++++++++++---------------
> kernel/cgroup.c | 62 +++++++++++++++++++++-------------------------
> kernel/exit.c | 16 ++++++++---
> kernel/fork.c | 8 ++---
> 5 files changed, 88 insertions(+), 65 deletions(-)
>
> --
> tejun
>
> [1] http://thread.gmane.org/gmane.linux.kernel/1187553
>


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