From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
To: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
Cc: Containers
<containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
Subject: Re: [PATCH][usercr]: Ghost tasks must be detached
Date: Wed, 9 Feb 2011 18:44:30 -0800 [thread overview]
Message-ID: <20110210024430.GA23167@us.ibm.com> (raw)
In-Reply-To: <4D520B78.9020300-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
Oren Laadan [orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org] wrote:
|
|
| > But if that is true, I need to investigate why Louis Rilling was getting
| > the crash in Jun 2010 - which he tried to fix here:
| >
| > http://lkml.org/lkml/2010/6/16/295
|
| I see. So basically there is a kerenl bug that can be potentially
| exposed by the c/r code. Therefore, we need to fix the kernel bug...
| (and until such a fix makes it to mainline, we'll add it as part of
| the linux-cr patchset).
Yes, but there is more than one problem (at least in our C/R kernel).
There is the bug that Louis Rilling reported and Eric has a fix for.
Even if we apply Eric's fix to the C/R kernel, we still will have
another problem if do_ghost_task() sets ->exit_signal to -1.
Consider this in 2.6.37:
Container-init: Ghost child of container-init
do_ghost_task()
zap_pid_ns..()
Send SIGKILL
do_wait()
- adds self to ->wait_chldexit queue
- goes through do_wait_thread() - finds that
it has at least one child (on tsk->children),
but it has not yet exited
- so waits for the child to exit
wakes up for SIGKILL
->exit_signal = -1
do_exit()
Note that exit_notify() does not notify parent when the ghost process
exits, because ->exit_signal is -1.
So you may ask how did the container-init have a ghost child. That was
due to a bug in usercr :-).
But my point is such a userspace bug can leave the above container init
unkillable.
Note that this does not happen with normal threads which set ->exit_signal
to -1 . That is because of the following two pieces of code in copy_process():
/* ok, now we should be set up.. */
p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
and
/* CLONE_PARENT re-uses the old parent */
if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
p->real_parent = current->real_parent;
p->parent_exec_id = current->parent_exec_id;
With this our container-init above will not have any children to wait
for in do_wait_thread().
Sukadev
next prev parent reply other threads:[~2011-02-10 2:44 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-11 3:35 [PATCH][usercr]: Ghost tasks must be detached Sukadev Bhattiprolu
[not found] ` <20101211033548.GA12584-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-01-11 1:51 ` Oren Laadan
[not found] ` <4D2BB78A.9090701-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2011-02-05 18:55 ` Oren Laadan
[not found] ` <4D4D9D1B.3000209-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2011-02-05 21:40 ` Sukadev Bhattiprolu
[not found] ` <20110205214032.GA12944-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-02-05 22:02 ` Oren Laadan
[not found] ` <4D4DC90B.3010103-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2011-02-05 22:33 ` Oren Laadan
2011-02-09 2:09 ` Sukadev Bhattiprolu
[not found] ` <20110209020942.GA5339-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-02-09 3:35 ` Oren Laadan
[not found] ` <4D520B78.9020300-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2011-02-10 2:44 ` Sukadev Bhattiprolu [this message]
[not found] ` <20110210024430.GA23167-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-02-10 3:53 ` Oren Laadan
[not found] ` <4D536154.8000900-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2011-02-10 6:17 ` Sukadev Bhattiprolu
[not found] ` <20110210061730.GA25432-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-02-10 14:56 ` Oren Laadan
[not found] ` <4D53FC9C.1050405-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2011-02-10 17:42 ` Sukadev Bhattiprolu
2011-02-16 20:10 ` Sukadev Bhattiprolu
[not found] ` <20110216201019.GA27698-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-02-17 15:21 ` Louis Rilling
[not found] ` <20110217152116.GM518-Hu8+6S1rdjywhHL9vcZdMVaTQe2KTcn/@public.gmane.org>
2011-02-21 20:40 ` Sukadev Bhattiprolu
[not found] ` <20110221204058.GC14377-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-02-22 10:28 ` Louis Rilling
2011-02-09 12:01 ` Louis Rilling
[not found] ` <20110209120100.GD13323-Hu8+6S1rdjywhHL9vcZdMVaTQe2KTcn/@public.gmane.org>
2011-02-09 12:18 ` Oren Laadan
[not found] ` <4D528629.7030905-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2011-02-09 12:35 ` Louis Rilling
[not found] ` <20110209123550.GG13323-Hu8+6S1rdjywhHL9vcZdMVaTQe2KTcn/@public.gmane.org>
2011-02-09 12:37 ` Louis Rilling
2011-02-09 19:02 ` Sukadev Bhattiprolu
[not found] ` <20110209190216.GA17051-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-02-10 10:23 ` Louis Rilling
[not found] ` <20110210102312.GC6360-Hu8+6S1rdjywhHL9vcZdMVaTQe2KTcn/@public.gmane.org>
2011-02-10 17:54 ` Sukadev Bhattiprolu
[not found] ` <20110210175409.GB1025-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-02-10 18:04 ` Louis Rilling
[not found] ` <20110210180433.GI6360-Hu8+6S1rdjywhHL9vcZdMVaTQe2KTcn/@public.gmane.org>
2011-02-10 22:31 ` Sukadev Bhattiprolu
2011-02-25 7:58 ` Sukadev Bhattiprolu
[not found] ` <20110225075808.GC24361-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2011-02-25 15:46 ` Oren Laadan
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