From: Oleg Nesterov <oleg@redhat.com>
To: Kirill Tkhai <tkhai@yandex.ru>
Cc: Kirill Tkhai <ktkhai@parallels.com>,
linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Vladimir Davydov <vdavydov@parallels.com>
Subject: Re: [PATCH RFC] sched: Revert delayed_put_task_struct() and fix use after free
Date: Fri, 17 Oct 2014 23:34:40 +0200 [thread overview]
Message-ID: <20141017213440.GA32576@redhat.com> (raw)
In-Reply-To: <543EEB1F.3040900@yandex.ru>
On 10/16, Kirill Tkhai wrote:
>
> Cool! Elegant fix. We set PF_EXITING in exit_signals(), which is earlier
> than release_task() is called.
OK, thanks, I am sending the patch...
> Shouldn't we use smp_rmb/smp_wmb here?
No, we do not. call_rcu(delayed_put_pid) itself implies the barrier on
all CPUs. IOW, by the time RCU actually calls delayed_put_pid() every
CPU must see all memory changes which were done before call_rcu() was
called. And otoh, all rcu-read-lock critical sections which could miss
PF_EXITING should be already finished.
Oleg.
next prev parent reply other threads:[~2014-10-17 21:38 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-15 12:31 [PATCH RFC] sched: Revert delayed_put_task_struct() and fix use after free Kirill Tkhai
2014-10-15 15:06 ` Oleg Nesterov
2014-10-15 19:40 ` Oleg Nesterov
2014-10-15 21:46 ` Kirill Tkhai
2014-10-15 22:02 ` Kirill Tkhai
2014-10-16 7:59 ` Peter Zijlstra
2014-10-16 8:16 ` Kirill Tkhai
2014-10-16 9:43 ` Peter Zijlstra
2014-10-16 9:50 ` Kirill Tkhai
2014-10-16 9:51 ` Kirill Tkhai
2014-10-16 10:04 ` Kirill Tkhai
2014-10-17 21:34 ` Oleg Nesterov [this message]
2014-10-16 7:56 ` Peter Zijlstra
2014-10-16 8:01 ` Peter Zijlstra
2014-10-16 22:05 ` Oleg Nesterov
2014-10-17 21:36 ` [PATCH] sched/numa: fix unsafe get_task_struct() in task_numa_assign() Oleg Nesterov
2014-10-18 8:15 ` Kirill Tkhai
2014-10-18 8:33 ` Kirill Tkhai
2014-10-18 19:36 ` Peter Zijlstra
2014-10-18 21:18 ` Oleg Nesterov
2014-10-19 8:20 ` Kirill Tkhai
2014-10-18 20:56 ` Oleg Nesterov
2014-10-18 23:13 ` Kirill Tkhai
2014-10-19 19:24 ` Oleg Nesterov
2014-10-19 19:37 ` Oleg Nesterov
2014-10-19 19:43 ` Oleg Nesterov
2014-10-20 9:03 ` Kirill Tkhai
2014-10-20 9:13 ` Peter Zijlstra
2014-10-20 10:36 ` Kirill Tkhai
2014-10-20 9:00 ` Kirill Tkhai
2014-10-19 21:38 ` Peter Zijlstra
2014-10-20 8:56 ` Kirill Tkhai
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