Messages in this thread | | | Date | Wed, 18 Apr 2012 02:29:56 +0000 | From | "Serge E. Hallyn" <> | Subject | Re: [PATCH] pidns: reboot_pid_ns: use SEND_SIG_FORCED instead of force_sig() |
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Quoting Oleg Nesterov (oleg@redhat.com): > On 04/16, Oleg Nesterov wrote: > > > > I'll investigate and report tomorrow. > > Thanks again Serge, everything is clear.
Phew :)
> Afaics this needs another > (almost off-topic) patch. > > Please forget about sys_reboot() for the moment. There is a minor > and known problem with SIGKILL && SIGNAL_UNKILLABLE. If you send > SIGKILL from the parent namespace to cinit, this doesn't make it > SIGNAL_GROUP_EXIT immediately. Only after cinit actually dequeues > SIGKILL it does do_group_exit() and set this flag. This should be > fixed anyway, but not now. > > And this explain the problem. Note that your test-case does > sys_reboot() from the init process, and reboot_pid_ns() does > > kill(pid_ns->child_reaper, SIGKILL); > > do_exit(0); > > so it sends SIGKILL to itself and exit. This means that cinit > (current) obviously can't dequeue SIGKILL, and without > SIGNAL_GROUP_EXIT wait_task_zombie() ignores > signal->group_exit_code. > > That is why the patch makes a difference. > > But why reboot_pid_ns() does do_exit? Yes, it was copied from > sys_reboot() and I didn't notice. It should use do_group_exit(), > and sys_reboot() too. This is the patch I am going to send, but > I'll try to think a bit more. > > Thanks! > > Oleg.
Great, glad it makes sense! :)
I'll test when you have a patch ready. Thanks, Oleg.
-serge
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