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    SubjectRe: [RFC, PATCH] handle the multi-threaded init's exit() properly
    On Tue, 7 Aug 2007 00:33:26 +0400 Oleg Nesterov <oleg@tv-sign.ru> wrote:

    > On 08/06, Andrew Morton wrote:
    > >
    > > On Fri, 3 Aug 2007 01:20:09 +0400 Oleg Nesterov <oleg@tv-sign.ru> wrote:
    > >
    > > > 2. We are playing games with ->nsproxy->pid_ns. This code is bogus today, and
    > > > it has to be changed anyway when we really support pid namespaces, just
    > > > remove it.
    > >
    > > This patch broke
    > >
    > > pid-namespaces-define-and-use-task_active_pid_ns-wrapper.patch. This hunk:
    > >
    > > ***************
    > > *** 908,915 ****
    > > if (unlikely(!tsk->pid))
    > > panic("Attempted to kill the idle task!");
    > > if (unlikely(tsk == child_reaper(tsk))) {
    > > - if (tsk->nsproxy->pid_ns != &init_pid_ns)
    > > - tsk->nsproxy->pid_ns->child_reaper = init_pid_ns.child_reaper;
    > > else
    > > panic("Attempted to kill init!");
    > > }
    > > --- 908,916 ----
    > > if (unlikely(!tsk->pid))
    > > panic("Attempted to kill the idle task!");
    > > if (unlikely(tsk == child_reaper(tsk))) {
    > > + if (task_active_pid_ns(tsk) != &init_pid_ns)
    > > + task_active_pid_ns(tsk)->child_reaper =
    > > + init_pid_ns.child_reaper;
    > > else
    > > panic("Attempted to kill init!");
    > > }
    > >
    > > has no place to live any more, so I just removed it.
    >
    > Ah, thanks. I should have done this patch against -mm tree.
    >
    > I hope it is OK to drop this chunk of
    > pid-namespaces-define-and-use-task_active_pid_ns-wrapper.patch
    >
    > Because it can't work right now anyway, and Sukadev+Pavel already have
    > new patches on top this one which make namespace switch actually work.
    >

    OK, well I had to make a bit of on-the-fly adjustment to
    pid-namespaces-rename-child_reaper-function.patch as well.

    The diff-of-the-diff is:

    @@ -48,7 +48,7 @@
    diff -puN kernel/exit.c~pid-namespaces-rename-child_reaper-function kernel/exit.c
    --- a/kernel/exit.c~pid-namespaces-rename-child_reaper-function
    +++ a/kernel/exit.c
    -@@ -694,7 +694,7 @@ forget_original_parent(struct task_struc
    +@@ -683,7 +683,7 @@ forget_original_parent(struct task_struc
    do {
    reaper = next_thread(reaper);
    if (reaper == father) {
    @@ -57,19 +57,10 @@
    break;
    }
    } while (reaper->exit_state);
    -@@ -907,7 +907,7 @@ fastcall NORET_TYPE void do_exit(long co
    - panic("Aiee, killing interrupt handler!");
    - if (unlikely(!tsk->pid))
    - panic("Attempted to kill the idle task!");
    -- if (unlikely(tsk == child_reaper(tsk))) {
    -+ if (unlikely(tsk == task_child_reaper(tsk))) {
    - if (task_active_pid_ns(tsk) != &init_pid_ns)
    - task_active_pid_ns(tsk)->child_reaper =
    - init_pid_ns.child_reaper;
    diff -puN kernel/signal.c~pid-namespaces-rename-child_reaper-function kernel/signal.c
    Hopefully people can re-review and retest what's there in next -mm.

    Or if that's too much work or too risky, option b) is to drop
    handle-the-multi-threaded-inits-exit-properly.patch, go back to the
    2.6.23-rc1-mm2 versions of
    pid-namespaces-define-and-use-task_active_pid_ns-wrapper.patch and
    pid-namespaces-rename-child_reaper-function.patch and to ask Oleg to cook a 2.6.23-rc1-mm2 version of handle-the-multi-threaded-inits-exit-properly.patch.

    The downside of this approach is that
    handle-the-multi-threaded-inits-exit-properly.patch looks more 2.6.24-ready
    than all the container stuff (based just on overall impact and
    speculativeness)

    -
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