[PATCH][cr]: Ghost tasks must not be detached in kernel
orenl at cs.columbia.edu
Mon Jan 10 17:51:20 PST 2011
Merged into v23-rc1.
On 12/10/2010 10:33 PM, Sukadev Bhattiprolu wrote:
> As discussed (a while ago)
> here is a patch. I will send a follow-on user-cr patch to mark
> the task detached in user-space.
> From: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
> Date: Fri, 10 Dec 2010 18:37:17 -0800
> Subject: [PATCH 1/1] Ghost tasks must not be detached in kernel
> Ghost tasks are "temporary" tasks created during sys_restart() to
> restore "orphaned" sessions/process groups (i.e. those in which the
> original session/pgrp leader had exited before checkpoint but other
> processes exist in that session/pgrp).
> We only create the ghost task so we have a valid session/pgrp that
> the other processes in the session/pgrp can use. Once those other
> processes are created, the ghost tasks must silently vanish (without
> sending another SIGCHLD).
> do_ghost_task() was setting the exit_signal to -1 so the ghosts don't
> send a signal. But rather than set the ->exit_signal here, the caller
> (i.e user-space) can create the ghost task by explicitly setting the
> CSIGNAL mask to 0xFF. i.e it is not something the we need to do in the
> The downside of marking the task detached in do_ghost_task() is that
> with current/older kernels container-init does not wait for detached
> tasks. See:
> This can lead to a kernel crash if the container-init pre-deceases a
> ghost task.
> Signed-off-by: Sukadev Bhattiprolu (sukadev at us.ibm.com)
> kernel/checkpoint/restart.c | 1 -
> 1 files changed, 0 insertions(+), 1 deletions(-)
> diff --git a/kernel/checkpoint/restart.c b/kernel/checkpoint/restart.c
> index 17270b8..2bb7197 100644
> --- a/kernel/checkpoint/restart.c
> +++ b/kernel/checkpoint/restart.c
> @@ -972,7 +972,6 @@ static int do_ghost_task(void)
> if (ret < 0)
> ckpt_err(ctx, ret, "ghost restart failed\n");
> - current->exit_signal = -1;
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