From: ebiederm@xmission.com (Eric W. Biederman)
To: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux Containers <containers@lists.osdl.org>,
linux-kernel@vger.kernel.org, Pavel Emelyanov <xemul@openvz.org>,
Oleg Nesterov <oleg@redhat.com>,
"Serge E. Hallyn" <serge@hallyn.com>
Subject: Re: [PATCH] pidns: Fix wait for zombies to be reaped in zap_pid_ns_processes
Date: Wed, 14 Jul 2010 14:35:52 -0700 [thread overview]
Message-ID: <m14og1oifb.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <20100714205324.GA13956@us.ibm.com> (Sukadev Bhattiprolu's message of "Wed\, 14 Jul 2010 13\:53\:24 -0700")
Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> writes:
> Eric W. Biederman [ebiederm@xmission.com] wrote:
> |
> | Changing zap_pid_ns_processes to fix the problem instead of
> | changing the code elsewhere is one of the few solutions I have
> | seen that does not increase the cost of the lat_proc test from
> | lmbench.
>
> I think its a good fix for the problem. but I have a nit and a minor
> comment below.
>
> Thanks,
>
> Sukadev
>
> |
> | Reported-by: Louis Rilling <Louis.Rilling@kerlabs.com>
>
> Reviewed-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
>
> | Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> | ---
> | kernel/pid_namespace.c | 50 ++++++++++++++++++++++++++++++++++++-----------
> | 1 files changed, 38 insertions(+), 12 deletions(-)
> |
> | diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
> | index a5aff94..aaf2ab0 100644
> | --- a/kernel/pid_namespace.c
> | +++ b/kernel/pid_namespace.c
> | @@ -139,16 +139,20 @@ void free_pid_ns(struct kref *kref)
> |
> | void zap_pid_ns_processes(struct pid_namespace *pid_ns)
> | {
> | + struct task_struct *me = current;
> | int nr;
> | int rc;
> | struct task_struct *task;
> |
> | /*
> | - * The last thread in the cgroup-init thread group is terminating.
> | - * Find remaining pid_ts in the namespace, signal and wait for them
> | - * to exit.
> | + * The last task in the pid namespace-init threa group is terminating.
>
> nit: thread
Agreed.
> | + * Find remaining pids in the namespace, signal and wait for them
> | + * to to be reaped.
> | *
> | - * Note: This signals each threads in the namespace - even those that
> | + * By waiting for all of the tasks to be reaped before init is reaped
> | + * we provide the invariant that no task can escape the pid namespace.
> | + *
> | + * Note: This signals each task in the namespace - even those that
> | * belong to the same thread group, To avoid this, we would have
> | * to walk the entire tasklist looking a processes in this
> | * namespace, but that could be unnecessarily expensive if the
> | @@ -157,28 +161,50 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
> | *
> | */
> | read_lock(&tasklist_lock);
> | - nr = next_pidmap(pid_ns, 1);
> | - while (nr > 0) {
> | - rcu_read_lock();
> | + for (nr = next_pidmap(pid_ns, 0); nr > 0; nr = next_pidmap(pid_ns, nr)) {
>
> Is it necessary to start the search at nr == 0 ? We will find nr == 1
> first and then immediately skip over it - bc same_thread_group() will
> be TRUE.
Which means we exercise that code path, and ensure we have same_thread_group
test working properly. Given how rare threaded inits are every little bit
of extra test coverage that doesn't really cost us anything seems important.
> | /*
> | * Any nested-container's init processes won't ignore the
> | * SEND_SIG_NOINFO signal, see send_signal()->si_fromuser().
> | */
> | - task = pid_task(find_vpid(nr), PIDTYPE_PID);
> | - if (task)
> | + rcu_read_lock();
> | + task = pid_task(find_pid_ns(nr, pid_ns), PIDTYPE_PID);
> | + if (task && !same_thread_group(task, me))
> | send_sig_info(SIGKILL, SEND_SIG_NOINFO, task);
>
> Also, if we start the search at 1, we could skip the only the other possible
> thread in the group with
>
> (nr != my_pid_nr)
>
> but its not really an optimization.
It is possible that other threads of a multi-threaded init are in the PF_EXITING
state and still visible for sending signals to. I really don't want to send
SIG_KILL to another thread of init. There is a chance of messing up the return
code if I do that, and do not want to need to think about that case.
Eric
next prev parent reply other threads:[~2010-07-14 21:36 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-16 16:34 [PATCH] procfs: Do not release pid_ns->proc_mnt too early Louis Rilling
2010-06-17 9:53 ` Pavel Emelyanov
2010-06-17 13:41 ` Eric W. Biederman
2010-06-17 14:20 ` Louis Rilling
2010-06-17 21:36 ` Oleg Nesterov
2010-06-18 8:27 ` Louis Rilling
2010-06-18 16:27 ` Oleg Nesterov
2010-06-21 11:11 ` Louis Rilling
2010-06-21 12:58 ` Eric W. Biederman
2010-06-21 14:15 ` Louis Rilling
2010-06-21 14:26 ` Eric W. Biederman
2010-06-17 21:20 ` Oleg Nesterov
2010-06-18 8:20 ` Louis Rilling
2010-06-18 11:15 ` Oleg Nesterov
2010-06-18 16:08 ` Oleg Nesterov
2010-06-18 17:33 ` Louis Rilling
2010-06-18 17:55 ` Oleg Nesterov
2010-06-18 21:23 ` Oleg Nesterov
2010-06-19 19:08 ` [PATCH 0/4] pid_ns_prepare_proc/unshare cleanups Oleg Nesterov
2010-06-19 19:09 ` [PATCH 1/4] procfs: proc_get_sb: consolidate/cleanup root_inode->pid logic Oleg Nesterov
2010-06-19 19:10 ` [PATCH 2/4] procfs: kill the global proc_mnt variable Oleg Nesterov
2010-06-19 19:10 ` [PATCH 3/4] procfs: move pid_ns_prepare_proc() from copy_process() to create_pid_namespace() Oleg Nesterov
2010-06-19 19:11 ` [PATCH RESEND 4/4] sys_unshare: simplify the not-really-implemented CLONE_THREAD/SIGHAND/VM code Oleg Nesterov
2010-06-20 8:42 ` [PATCH 0/6] Unshare support for the pid namespace Eric W. Biederman
2010-06-20 8:44 ` [PATCH 1/6] pid: Remove the child_reaper special case in init/main.c Eric W. Biederman
2010-06-20 18:29 ` Oleg Nesterov
2010-06-20 20:27 ` Oleg Nesterov
2010-06-20 8:45 ` [PATCH 2/6] pidns: Call pid_ns_prepare_proc from create_pid_namespace Eric W. Biederman
2010-06-20 18:19 ` Oleg Nesterov
2010-06-20 8:45 ` [PATCH 3/6] procfs: kill the global proc_mnt variable Eric W. Biederman
2010-06-20 8:47 ` [PATCH 4/6] pidns: Don't allow new pids after the namespace is dead Eric W. Biederman
2010-06-20 18:44 ` Oleg Nesterov
2010-06-20 8:48 ` [PATCH 5/6] pidns: Use task_active_pid_ns where appropriate Eric W. Biederman
2010-06-20 8:49 ` [PATCH 6/6] pidns: Support unsharing the pid namespace Eric W. Biederman
2010-06-20 20:14 ` Oleg Nesterov
2010-06-20 20:42 ` Oleg Nesterov
2010-06-21 1:53 ` Eric W. Biederman
2010-06-20 18:03 ` [PATCH 0/6] Unshare support for " Oleg Nesterov
2010-06-20 18:05 ` [PATCH 0/2] pid_ns_release_proc() fixes Oleg Nesterov
2010-06-20 18:06 ` [PATCH 1/2] pid_ns: move destroy_pid_namespace() into workqueue context Oleg Nesterov
2010-06-20 18:06 ` [PATCH 2/2] pid_ns: refactor the buggy pid_ns_release_proc() logic Oleg Nesterov
2010-06-20 21:00 ` [PATCH 0/6] Unshare support for the pid namespace Eric W. Biederman
2010-06-20 21:48 ` Oleg Nesterov
2010-06-20 21:56 ` Oleg Nesterov
2011-01-26 15:57 ` Daniel Lezcano
2010-06-23 20:36 ` [PATCH 0/1] pid_ns: move pid_ns_release_proc() from proc_flush_task() to zap_pid_ns_processes() Oleg Nesterov
2010-06-23 20:37 ` [PATCH 1/1] " Oleg Nesterov
2010-06-24 6:36 ` Sukadev Bhattiprolu
2010-06-24 12:59 ` Oleg Nesterov
2010-06-24 7:06 ` Eric W. Biederman
2010-06-24 13:01 ` Oleg Nesterov
2010-06-24 8:37 ` [PATCH] pid_ns: Fix proc_flush_task() accessing freed proc_mnt Louis Rilling
2010-06-24 17:08 ` [RESEND PATCH] " Louis Rilling
2010-06-24 19:18 ` Oleg Nesterov
2010-06-25 10:23 ` Louis Rilling
2010-06-25 12:21 ` Oleg Nesterov
2010-06-25 18:37 ` Sukadev Bhattiprolu
2010-06-25 19:29 ` Oleg Nesterov
2010-06-25 21:26 ` Sukadev Bhattiprolu
2010-06-25 21:27 ` Oleg Nesterov
2010-06-25 22:07 ` Sukadev Bhattiprolu
2010-07-09 4:36 ` [RFC][PATCH 1/2] pidns: Add a flag to indicate a pid namespace is dead Eric W. Biederman
2010-07-09 4:39 ` [RFC][PATCH 2/2] pidns: Remove proc flush races when a pid namespaces are exiting Eric W. Biederman
2010-07-09 12:14 ` Louis Rilling
2010-07-09 13:05 ` Eric W. Biederman
2010-07-09 14:13 ` Louis Rilling
2010-07-09 15:58 ` [PATCH 01/24] pidns: Remove races by stopping the caching of proc_mnt Eric W. Biederman
2010-07-09 22:13 ` Serge E. Hallyn
2010-07-11 14:14 ` Louis Rilling
2010-07-11 14:25 ` Eric W. Biederman
2010-07-12 18:09 ` [PATCH] pidns: Fix wait for zombies to be reaped in zap_pid_ns_processes Eric W. Biederman
2010-07-13 21:42 ` Louis Rilling
2010-07-13 22:34 ` Serge E. Hallyn
2010-07-14 1:47 ` Eric W. Biederman
2010-10-30 7:07 ` Sukadev Bhattiprolu
2010-07-14 20:53 ` Sukadev Bhattiprolu
2010-07-14 21:35 ` Eric W. Biederman [this message]
2010-06-21 11:09 ` [PATCH] procfs: Do not release pid_ns->proc_mnt too early Louis Rilling
2010-06-21 11:15 ` Louis Rilling
2010-06-21 14:38 ` Oleg Nesterov
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