From: "Paul E. McKenney" <paulmck@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Frederic Weisbecker <frederic@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 06:34:45 -0800 [thread overview]
Message-ID: <20221207143445.GA4001@paulmck-ThinkPad-P17-Gen-1> (raw)
In-Reply-To: <20221206164927.GD3866@redhat.com>
On Tue, Dec 06, 2022 at 05:49:28PM +0100, Oleg Nesterov wrote:
> On 11/30, Eric W. Biederman wrote:
> >
> > 2) I keep thinking zap_pid_ns_processes() should be changed so that
> > after it sends SIGKILL to all of the relevant processes to not wait,
>
> 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.
>
> Say we create a task P using clone(CLONE_NEWPID), then inject a task T into
> P's pid-namespace via setns/fork. This make the process P "unkillable", it
> will hang in zap_pid_ns_processes() "forever" until T->parent reaps a zombie
> task T killed by P.
Given that this is not the first time that Tasks Trace RCU has been
involved in a deadlock involving this exit path, I could certainly get
behind this approach. ;-)
Thanx, Paul
next prev parent reply other threads:[~2022-12-07 14:34 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 [this message]
2022-12-07 20:01 ` Frederic Weisbecker
2022-12-07 20:39 ` Oleg Nesterov
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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