Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1758301Ab2JYHGj (ORCPT <rfc822;w@1wt.eu>);
	Thu, 25 Oct 2012 03:06:39 -0400
Received: from mail-vc0-f174.google.com ([209.85.220.174]:46485 "EHLO
	mail-vc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1756593Ab2JYHGg (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 25 Oct 2012 03:06:36 -0400
MIME-Version: 1.0
In-Reply-To: <20121025055056.GA2661@swordfish>
References: <20121017034918.GA13295@redhat.com>
	<20121024164235.GA2467@swordfish>
	<20121024180608.GA22840@redhat.com>
	<20121024182111.GA2340@swordfish>
	<CAFTL4hxmh7yV8ePUhY_7hOuG=JrbZZcNvV88bWcUmwG9X0W04A@mail.gmail.com>
	<20121025055056.GA2661@swordfish>
Date: Thu, 25 Oct 2012 09:06:36 +0200
Message-ID: <CAFTL4hxM8KqL3=GLkJDU-9pKVHrb1nSoDgFx8UVB7F7tryw6HA@mail.gmail.com>
Subject: Re: lots of suspicious RCU traces
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>, Dave Jones <davej@redhat.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        linux-kernel@vger.kernel.org
Content-Type: text/plain; charset=ISO-8859-1
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1518
Lines: 38

2012/10/25 Sergey Senozhatsky <sergey.senozhatsky@gmail.com>:
> On (10/25/12 00:32), Frederic Weisbecker wrote:
>> First of all, thanks a lot for your report.
>>
>> 2012/10/24 Sergey Senozhatsky <sergey.senozhatsky@gmail.com>:
>> > On (10/24/12 20:06), Oleg Nesterov wrote:
>> >> On 10/24, Sergey Senozhatsky wrote:
>> >> >
>> >> > small question,
>> >> >
>> >> > ptrace_notify() and forward calls are able to both indirectly and directly call schedule(),
>> >> > /* direct call from ptrace_stop()*/,
>> >> > should, in this case, rcu_user_enter() be called before tracehook_report_syscall_exit(regs, step)
>> >> > and ptrace chain?
>> >>
>> >> Well, I don't really understand this magic... but why?
>> >>
>> >
>> > My understanding is (I may be wrong) that we can schedule() from ptrace chain to
>> > some arbitrary task, which will continue its execution from the point where RCU assumes
>> > CPU as not idle, while CPU in fact still in idle state -- no one said rcu_idle_exit()
>> > (or similar) prior to schedule() call.
>>
>> Yeah but when we are in syscall_trace_leave(), the CPU shouldn't be in
>> RCU idle mode. That's where the bug is. How do you manage to trigger
>> this bug?
>>
>
> strace -f <anything>

I can't reproduce. Can you send me your config?

Thanks.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/