From: Oleg Nesterov <oleg@redhat.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Don Zickus <dzickus@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@elte.hu>,
Jerome Marchand <jmarchan@redhat.com>,
Mandeep Singh Baines <msb@google.com>,
Roland McGrath <roland@redhat.com>,
linux-kernel@vger.kernel.org, stable@kernel.org,
"Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: while_each_thread() under rcu_read_lock() is broken?
Date: Fri, 25 Jun 2010 11:55:48 +0200 [thread overview]
Message-ID: <20100625095548.GA6292@redhat.com> (raw)
In-Reply-To: <20100625034105.GD2391@linux.vnet.ibm.com>
On 06/24, Paul E. McKenney wrote:
>
> On Thu, Jun 24, 2010 at 11:57:02PM +0200, Oleg Nesterov wrote:
> > On 06/24, Paul E. McKenney wrote:
> > >
> > > 4. Some other thread might do pthread_exit(), removing itself
> > > from the thread group, and again might do so while the hapless
> > > reader is referencing that thread. In this case, we want
> > > the hapless reader to continue scanning the remainder of the
> > > thread group.
> >
> > Yes.
> >
> > But, if that thread was used as a starting point g, then
> >
> > before the patch: loop forever
> > after the patch: break
>
> So it is OK to skip some of the other threads in this case, even
> though they were present throughout the whole procedure?
I think, yes. We can miss them in any case, they can go away before
while_each_thread(g, t) starts the scan.
If g == group_leader (old or new), then we should notice this thread
at least.
Otherwise we can miss them all, with or without next_thread_careful().
Oleg.
next prev parent reply other threads:[~2010-06-25 9:57 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-18 19:02 [PATCH] fix the racy check_hung_uninterruptible_tasks()->rcu_lock_break() logic Oleg Nesterov
2010-06-18 19:34 ` while_each_thread() under rcu_read_lock() is broken? Oleg Nesterov
2010-06-18 21:08 ` Roland McGrath
2010-06-18 22:37 ` Oleg Nesterov
2010-06-18 22:33 ` Paul E. McKenney
2010-06-21 17:09 ` Oleg Nesterov
2010-06-21 17:44 ` Oleg Nesterov
2010-06-21 18:00 ` Oleg Nesterov
2010-06-21 19:02 ` Roland McGrath
2010-06-21 20:06 ` Oleg Nesterov
2010-06-21 21:19 ` Eric W. Biederman
2010-06-22 14:34 ` Oleg Nesterov
2010-07-08 23:59 ` Roland McGrath
2010-07-09 0:41 ` Paul E. McKenney
2010-07-09 1:01 ` Roland McGrath
2010-07-09 16:18 ` Paul E. McKenney
2010-06-21 20:51 ` Paul E. McKenney
2010-06-21 21:22 ` Eric W. Biederman
2010-06-21 21:38 ` Paul E. McKenney
2010-06-22 21:23 ` Oleg Nesterov
2010-06-22 22:12 ` Paul E. McKenney
2010-06-23 15:24 ` Oleg Nesterov
2010-06-24 18:07 ` Paul E. McKenney
2010-06-24 18:50 ` Chris Friesen
2010-06-24 22:00 ` Oleg Nesterov
2010-06-25 0:08 ` Eric W. Biederman
2010-06-25 3:42 ` Paul E. McKenney
2010-06-25 10:08 ` Oleg Nesterov
2010-07-09 0:52 ` Roland McGrath
2010-06-24 21:14 ` Roland McGrath
2010-06-25 3:37 ` Paul E. McKenney
2010-07-09 0:41 ` Roland McGrath
2010-06-24 21:57 ` Oleg Nesterov
2010-06-25 3:41 ` Paul E. McKenney
2010-06-25 9:55 ` Oleg Nesterov [this message]
2010-06-28 23:43 ` Paul E. McKenney
2010-06-29 13:05 ` Oleg Nesterov
2010-06-29 15:34 ` Paul E. McKenney
2010-06-29 17:54 ` Oleg Nesterov
2010-06-19 5:00 ` Mandeep Baines
2010-06-19 5:35 ` Frederic Weisbecker
2010-06-19 15:44 ` Mandeep Baines
2010-06-19 19:19 ` Oleg Nesterov
2010-06-18 20:11 ` [PATCH] fix the racy check_hung_uninterruptible_tasks()->rcu_lock_break() logic Frederic Weisbecker
2010-06-18 20:38 ` Mandeep Singh Baines
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