Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1754750Ab3ESUXh (ORCPT <rfc822;w@1wt.eu>);
	Sun, 19 May 2013 16:23:37 -0400
Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:8350 "EHLO
	hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754486Ab3ESUX2 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Sun, 19 May 2013 16:23:28 -0400
X-Authority-Analysis: v=2.0 cv=DKcNElxb c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=VaqywNGxpRkA:10 a=5SG0PmZfjMsA:10 a=IkcTkHD0fZMA:10 a=meVymXHHAAAA:8 a=l0Yg3AS2bs0A:10 a=i7dmgaDrw6K13tw0tm0A:9 a=QEXdDO2ut3YA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117
X-Cloudmark-Score: 0
X-Authenticated-User: 
X-Originating-IP: 74.67.115.198
Message-ID: <1368995002.6828.117.camel@gandalf.local.home>
Subject: Re: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep
From: Steven Rostedt <rostedt@goodmis.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>, David Howells <dhowells@redhat.com>,
        Hirokazu Takata <takata@linux-m32r.org>,
        Michal Simek <monstr@monstr.eu>,
        Koichi Yasutake <yasutake.koichi@jp.panasonic.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>, Chris Metcalf <cmetcalf@tilera.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Arnd Bergmann <arnd@arndb.de>, linux-arm-kernel@lists.infradead.org,
        linux-m32r@ml.linux-m32r.org, linux-m32r-ja@ml.linux-m32r.org,
        microblaze-uclinux@itee.uq.edu.au, linux-am33-list@redhat.com,
        linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org,
        linux-mm@kvack.org, kvm@vger.kernel.org
Date: Sun, 19 May 2013 16:23:22 -0400
In-Reply-To: <20130519164009.GA2434@redhat.com>
References: <cover.1368702323.git.mst@redhat.com>
	 <1f85dc8e6a0149677563a2dfb4cef9a9c7eaa391.1368702323.git.mst@redhat.com>
	 <20130516184041.GP19669@dyad.programming.kicks-ass.net>
	 <20130519093526.GD19883@redhat.com>
	 <1368966844.6828.111.camel@gandalf.local.home>
	 <20130519133418.GA24381@redhat.com>
	 <1368979579.6828.114.camel@gandalf.local.home>
	 <20130519164009.GA2434@redhat.com>
Content-Type: text/plain; charset="UTF-8"
X-Mailer: Evolution 3.4.4-3 
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 985
Lines: 28

On Sun, 2013-05-19 at 19:40 +0300, Michael S. Tsirkin wrote:

> OK I get it. So let me correct myself. The simple code
> that does something like this under a spinlock:
> >       preempt_disable
> >       pagefault_disable
> >       error = copy_to_user
> >       pagefault_enable
> >       preempt_enable
> >
> is not doing anything wrong and should not get a warning,
> as long as error is handled correctly later.
> Right?

I came in mid thread and I don't know the context. Anyway, the above
looks to me as you just don't want to sleep. If you try to copy data to
user space that happens not to be currently mapped for any reason, you
will get an error. Even if the address space is completely valid. Is
that what you want?

-- Steve


--
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/