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Re: [PATCH 14/15] Destroy pid namespace on init's death [message #15417 is a reply to message #15377]

Mon, 30 July 2007 11:56

Pavel Emelianov
Messages: 1149
Registered: September 2006

Senior Member

Oleg Nesterov wrote:
> On 07/26, Pavel Emelyanov wrote:
>> @@ -895,6 +915,7 @@ fastcall NORET_TYPE void do_exit(long co
>> {
>> struct task_struct *tsk = current;
>> int group_dead;
>> + struct pid_namespace *pid_ns = tsk->nsproxy->pid_ns;
>>
>> profile_task_exit(tsk);
>>
>> @@ -905,9 +926,10 @@ fastcall NORET_TYPE void do_exit(long co
>> if (unlikely(!tsk->pid))
>> panic("Attempted to kill the idle task!");
>> 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;
>> + if (pid_ns != &init_pid_ns) {
>> + zap_pid_ns_processes(pid_ns);
>> + pid_ns->child_reaper = init_pid_ns.child_reaper;
>> + }
>> else
>> panic("Attempted to kill init!");
>
> No, no, this is wrong. Yes, the current code is buggy too, I'll send
> the fix.
>
> I think this code should be moved below under the "if (group_dead)",
> and we should use tsk->group_leader.
>
>> +void zap_pid_ns_processes(struct pid_namespace *pid_ns)
>> +{
>> + int i;
>> + int nr;
>> + int nfree;
>> + int options = WNOHANG|WEXITED|__WALL;
>> +
>> +repeat:
>> + /*
>> + * We know pid == 1 is terminating. Find remaining pid_ts
>> + * in the namespace, signal them and then wait for them
>> + * exit.
>> + */
>> + nr = next_pidmap(pid_ns, 1);
>> + while (nr > 0) {
>> + kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr);
>> + nr = next_pidmap(pid_ns, nr);
>> + }
>> +
>> + nr = next_pidmap(pid_ns, 1);
>> + while (nr > 0) {
>> + do_wait(nr, options, NULL, NULL, NULL);
>
> When the first child of init exits, it sends SIGCHLD. After that,
> do_wait() will never sleep, so we are doing a busy-wait loop.
> Not good, especially when we have a niced child, can livelock.
>
>> + nr = next_pidmap(pid_ns, nr);
>> + }
>> +
>> + nfree = 0;
>> + for (i = 0; i < PIDMAP_ENTRIES; i++)
>> + nfree += atomic_read(&pid_ns->pidmap[i].nr_free);
>> +
>> + /*
>> + * If pidmap has entries for processes other than 0 and 1, retry.
>> + */
>> + if (nfree < (BITS_PER_PAGE * PIDMAP_ENTRIES - 2))
>> + goto repeat;
>
> This doesn't look right.
>
> Suppose that some "struct pid" was pinned from the parent namespace.
> In that case zap_pid_ns_processes() will burn CPU until put_pid(), bad.

Nope. struct pid can be pinned, but the pidmap "fingerprint" cannot.
So as soon as the release_task() is called the pidmap becomes free and
we can proceed.

However I agree with the "burn CPU" issue - wait must sleep if needed.

> I think we can rely on forget_original_child() and do something like
> this:
>
> zap_active_ns_processes(void)
> {
> // kill all tasks in our ns and below
> kill(-1, SIGKILL);

That would be too slow to walk through all the tasks in a node searching
for a couple of them we need. fing_ge_pid() looks better to me.

> do {
> clear_thread_flag(TIF_SIGPENDING);
> } while (wait(NULL) != -ECHLD);
> }
>
> Oleg.
>
>

Thanks,
Pavel

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[Message index]

		[RFC][PATCH 0/15] Pid namespaces By: Pavel Emelianov on Thu, 26 July 2007 14:45
		[PATCH 1/15] Move exit_task_namespaces() By: Pavel Emelianov on Thu, 26 July 2007 14:46
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Oleg Nesterov on Thu, 26 July 2007 16:47
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Oleg Nesterov on Fri, 27 July 2007 08:07
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Pavel Emelianov on Fri, 27 July 2007 08:24
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Oleg Nesterov on Fri, 27 July 2007 08:35
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Pavel Emelianov on Fri, 27 July 2007 08:37
		Re: [PATCH 1/15] Move exit_task_namespaces() By: dev on Thu, 26 July 2007 16:59
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Dave Hansen on Thu, 26 July 2007 16:10
		Re: [PATCH 1/15] Move exit_task_namespaces() By: xemul on Fri, 27 July 2007 06:38
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Oleg Nesterov on Thu, 02 August 2007 16:18
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Pavel Emelianov on Mon, 06 August 2007 08:00
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Oleg Nesterov on Mon, 06 August 2007 09:54
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Pavel Emelianov on Mon, 06 August 2007 09:58
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Oleg Nesterov on Mon, 06 August 2007 10:38
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Pavel Emelianov on Mon, 06 August 2007 11:21
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Oleg Nesterov on Mon, 06 August 2007 12:52
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Pavel Emelianov on Mon, 06 August 2007 13:38
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Pavel Emelianov on Mon, 06 August 2007 11:29
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Oleg Nesterov on Mon, 06 August 2007 12:48
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Pavel Emelianov on Mon, 06 August 2007 13:36
		Re: [PATCH 1/15] Move exit_task_namespaces() By: Oleg Nesterov on Mon, 06 August 2007 13:55
		[PATCH 2/15] Introduce MS_KERNMOUNT flag By: Pavel Emelianov on Thu, 26 July 2007 14:47
		[PATCH 3/15] kern_siginfo helper By: Pavel Emelianov on Thu, 26 July 2007 14:48
		Re: [PATCH 3/15] kern_siginfo helper By: Oleg Nesterov on Sun, 29 July 2007 11:40
		Re: [PATCH 3/15] kern_siginfo helper By: Pavel Emelianov on Mon, 30 July 2007 06:07
		Re: [PATCH 3/15] kern_siginfo helper By: Sukadev Bhattiprolu on Tue, 31 July 2007 00:21
		[PATCH 4/15] Make proc_flust_task() flush entries from multiple proc trees By: Pavel Emelianov on Thu, 26 July 2007 14:48
		[PATCH 5/15] Introduce struct upid By: Pavel Emelianov on Thu, 26 July 2007 14:49
		Re: [PATCH 5/15] Introduce struct upid By: Oleg Nesterov on Sun, 29 July 2007 09:50
		Re: [PATCH 5/15] Introduce struct upid By: Pavel Emelianov on Mon, 30 July 2007 05:58
		[PATCH 6/15] Make alloc_pid(), free_pid() and put_pid() work with struct upid By: Pavel Emelianov on Thu, 26 July 2007 14:50
		Re: [PATCH 6/15] Make alloc_pid(), free_pid() and put_pid() work with struct upid By: Oleg Nesterov on Sun, 29 July 2007 10:14
		Re: [PATCH 6/15] Make alloc_pid(), free_pid() and put_pid() work with struct upid By: Pavel Emelianov on Mon, 30 July 2007 06:03
		[PATCH 7/15] Helpers to obtain pid numbers By: Pavel Emelianov on Thu, 26 July 2007 14:51
		Re: [PATCH 7/15] Helpers to obtain pid numbers By: Dave Hansen on Thu, 26 July 2007 19:03
		Re: [PATCH 7/15] Helpers to obtain pid numbers By: Pavel Emelianov on Fri, 27 July 2007 06:40
		Re: [PATCH 7/15] Helpers to obtain pid numbers By: Oleg Nesterov on Sun, 29 July 2007 12:08
		Re: [PATCH 7/15] Helpers to obtain pid numbers By: Pavel Emelianov on Mon, 30 July 2007 06:11
		[PATCH 8/15] Helpers to find the task by its numerical ids By: Pavel Emelianov on Thu, 26 July 2007 14:51
		Re: [PATCH 8/15] Helpers to find the task by its numerical ids By: Dave Hansen on Thu, 26 July 2007 19:05
		Re: [PATCH 8/15] Helpers to find the task by its numerical ids By: Pavel Emelianov on Fri, 27 July 2007 06:43
		Re: [PATCH 8/15] Helpers to find the task by its numerical ids By: Oleg Nesterov on Sun, 29 July 2007 12:39
		Re: [PATCH 8/15] Helpers to find the task by its numerical ids By: Pavel Emelianov on Mon, 30 July 2007 06:15
		[PATCH 9/15] Move alloc_pid() after the namespace is cloned By: Pavel Emelianov on Thu, 26 July 2007 14:52
		Re: [PATCH 9/15] Move alloc_pid() after the namespace is cloned By: Oleg Nesterov on Fri, 27 July 2007 15:10
		Re: [PATCH 9/15] Move alloc_pid() after the namespace is cloned By: Pavel Emelianov on Mon, 30 July 2007 06:17
		Re: [PATCH 9/15] Move alloc_pid() after the namespace is cloned By: Sukadev Bhattiprolu on Mon, 30 July 2007 23:43
		Re: [PATCH 9/15] Move alloc_pid() after the namespace is cloned By: Sukadev Bhattiprolu on Tue, 31 July 2007 05:49
		[PATCH 10/15] Make each namespace has its own proc tree By: Pavel Emelianov on Thu, 26 July 2007 14:54
		Re: [PATCH 10/15] Make each namespace has its own proc tree By: Oleg Nesterov on Sun, 29 July 2007 15:56
		Re: [PATCH 10/15] Make each namespace has its own proc tree By: Oleg Nesterov on Sun, 29 July 2007 17:02
		Re: [PATCH 10/15] Make each namespace has its own proc tree By: Pavel Emelianov on Mon, 30 July 2007 06:45
		Re: [PATCH 10/15] Make each namespace has its own proc tree By: Pavel Emelianov on Mon, 30 July 2007 06:43
		[PATCH 11/15] Signal semantics By: Pavel Emelianov on Thu, 26 July 2007 14:55
		Re: [PATCH 11/15] Signal semantics By: Oleg Nesterov on Fri, 27 July 2007 12:30
		Re: [PATCH 11/15] Signal semantics By: Pavel Emelianov on Fri, 27 July 2007 13:38
		Re: [PATCH 11/15] Signal semantics By: serue on Fri, 27 July 2007 19:59
		Re: [PATCH 11/15] Signal semantics By: Sukadev Bhattiprolu on Fri, 27 July 2007 20:23
		Re: [PATCH 11/15] Signal semantics By: Pavel Emelianov on Mon, 30 July 2007 09:34
		Re: [PATCH 11/15] Signal semantics By: Pavel Emelianov on Mon, 30 July 2007 09:31
		Re: [PATCH 11/15] Signal semantics By: serue on Wed, 01 August 2007 16:13
		Re: [PATCH 11/15] Signal semantics By: dev on Thu, 02 August 2007 08:35
		Re: [PATCH 11/15] Signal semantics By: serue on Thu, 02 August 2007 20:09
		Re: [PATCH 11/15] Signal semantics By: Oleg Nesterov on Sun, 29 July 2007 11:23
		[PATCH 12/15] Miscelaneous stuff for pid namespaces By: Pavel Emelianov on Thu, 26 July 2007 14:56
		Re: [PATCH 12/15] Miscelaneous stuff for pid namespaces By: Pavel Emelianov on Fri, 27 July 2007 06:53
		Re: [PATCH 12/15] Miscelaneous stuff for pid namespaces By: Sukadev Bhattiprolu on Fri, 27 July 2007 06:22
		[PATCH 13/15] Clone the pid namespace By: Pavel Emelianov on Thu, 26 July 2007 14:56
		[PATCH 14/15] Destroy pid namespace on init's death By: Pavel Emelianov on Thu, 26 July 2007 14:57
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Sun, 29 July 2007 10:39
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Pavel Emelianov on Mon, 30 July 2007 11:56
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Mon, 30 July 2007 15:44
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Tue, 31 July 2007 09:07
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Sukadev Bhattiprolu on Wed, 01 August 2007 06:16
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Dave Hansen on Wed, 01 August 2007 16:00
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Wed, 01 August 2007 19:51
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: dev on Thu, 02 August 2007 08:37
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Thu, 02 August 2007 16:08
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Thu, 02 August 2007 17:08
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Sukadev Bhattiprolu on Fri, 03 August 2007 06:22
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Fri, 03 August 2007 10:55
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Sukadev Bhattiprolu on Thu, 02 August 2007 07:37
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Wed, 01 August 2007 19:48
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Sukadev Bhattiprolu on Thu, 02 August 2007 07:29
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Thu, 02 August 2007 15:39
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Sukadev Bhattiprolu on Thu, 02 August 2007 17:20
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Thu, 02 August 2007 17:29
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Sukadev Bhattiprolu on Thu, 02 August 2007 18:36
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Oleg Nesterov on Thu, 02 August 2007 18:49
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: serue on Thu, 02 August 2007 19:13
		Re: [PATCH 14/15] Destroy pid namespace on init's death By: Sukadev Bhattiprolu on Fri, 03 August 2007 21:36
		[PATCH 15/15] Hooks over the code to show correct values to user By: Pavel Emelianov on Thu, 26 July 2007 14:58
		Re: [PATCH 15/15] Hooks over the code to show correct values to user By: Sukadev Bhattiprolu on Fri, 27 July 2007 05:57
		Re: [PATCH 15/15] Hooks over the code to show correct values to user By: Pavel Emelianov on Fri, 27 July 2007 06:44
		Re: [PATCH 15/15] Hooks over the code to show correct values to user By: Oleg Nesterov on Sun, 29 July 2007 14:29
		Re: [PATCH 15/15] Hooks over the code to show correct values to user By: Pavel Emelianov on Mon, 30 July 2007 06:49
		Re: [PATCH 15/15] Hooks over the code to show correct values to user By: Oleg Nesterov on Tue, 31 July 2007 10:04
		Re: [RFC][PATCH 0/15] Pid namespaces By: Sukadev Bhattiprolu on Fri, 27 July 2007 04:22
		Re: [RFC][PATCH 0/15] Pid namespaces By: Sukadev Bhattiprolu on Fri, 27 July 2007 06:08
		Re: [RFC][PATCH 0/15] Pid namespaces By: Pavel Emelianov on Fri, 27 July 2007 06:47

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