From: Oleg Nesterov <oleg@redhat.com>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
Pengfei Xu <pengfei.xu@intel.com>,
Boqun Feng <boqun.feng@gmail.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
rcu@vger.kernel.org
Subject: Re: [PATCH 3/3] rcu-tasks: Fix synchronize_rcu_tasks() VS zap_pid_ns_processes()
Date: Wed, 7 Dec 2022 21:39:00 +0100 [thread overview]
Message-ID: <20221207203859.GD5421@redhat.com> (raw)
In-Reply-To: <20221207200155.GA1840475@lothringen>
Frederic,
before anything else, your patches look good to me, it is not that
I tried to argue!
On 12/07, Frederic Weisbecker wrote:
>
> On Tue, Dec 06, 2022 at 05:49:28PM +0100, Oleg Nesterov wrote:
> >
> > At least I think it should not wait for the tasks injected into this ns.
> >
> > Because this looks like a kernel bug even if we forget about this deadlock.
> >
> I think this was made that way on purpose,
Well maybe. But to me we have this behaviour only because we (me at least)
do not know how to avoid the "hang" in this case.
> see the comment in zap_pid_ns_processes():
Heh ;) I wrote this comment in a53b83154914 ("exit: pidns: fix/update the
comments in zap_pid_ns_processes()") exactly because I didn't like this
behaviour, but I thought it must be documented.
> I can't say I like the fact that a parent not belonging to a new namespace
> can create more than one child within that namespace
not sure I understand but this looks fine and useful to me,
> but anyway this all look like an ABI that can't be reverted now.
perhaps... But you know, I wrote my previous email because 2 weeks ago
I had to investigate a bug report which blamed the kernel, while the
problem (unkillable process sleeping in zap_pid_ns_processes) was caused
by the dangling zombie injected into that process's namespace. And I am
still trying to convince the customer they need to fix userspace.
Thanks,
Oleg.
next prev parent reply other threads:[~2022-12-07 20:40 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-25 13:54 [PATCH 0/3] rcu-tasks: Fix race against exiting pid_ns Frederic Weisbecker
2022-11-25 13:54 ` [PATCH 1/3] rcu-tasks: Improve comments explaining tasks_rcu_exit_srcu purpose Frederic Weisbecker
2022-11-25 13:54 ` [PATCH 2/3] rcu-tasks: Remove preemption disablement around srcu_read_[un]lock() calls Frederic Weisbecker
2022-11-25 13:55 ` [PATCH 3/3] rcu-tasks: Fix synchronize_rcu_tasks() VS zap_pid_ns_processes() Frederic Weisbecker
2022-11-30 18:37 ` Eric W. Biederman
2022-12-02 19:51 ` Paul E. McKenney
2022-12-02 22:54 ` Frederic Weisbecker
2022-12-02 23:28 ` Eric W. Biederman
2022-12-04 0:03 ` Frederic Weisbecker
2022-12-06 16:49 ` Oleg Nesterov
2022-12-07 14:34 ` Paul E. McKenney
2022-12-07 20:01 ` Frederic Weisbecker
2022-12-07 20:39 ` Oleg Nesterov [this message]
2022-12-09 20:26 ` Frederic Weisbecker
2022-11-29 0:22 ` [PATCH 0/3] rcu-tasks: Fix race against exiting pid_ns Paul E. McKenney
2022-11-29 9:55 ` Frederic Weisbecker
2022-11-29 14:48 ` Paul E. McKenney
2022-12-02 22:55 ` Frederic Weisbecker
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