Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754637Ab3ESMeN (ORCPT ); Sun, 19 May 2013 08:34:13 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:22274 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751499Ab3ESMeJ (ORCPT ); Sun, 19 May 2013 08:34:09 -0400 X-Authority-Analysis: v=2.0 cv=UY7TuduN 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=Yl-b3-1lNjR0Stw38eQA:9 a=QEXdDO2ut3YA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-ID: <1368966844.6828.111.camel@gandalf.local.home> Subject: Re: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep From: Steven Rostedt To: "Michael S. Tsirkin" Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , David Howells , Hirokazu Takata , Michal Simek , Koichi Yasutake , Benjamin Herrenschmidt , Paul Mackerras , Chris Metcalf , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Arnd Bergmann , 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 08:34:04 -0400 In-Reply-To: <20130519093526.GD19883@redhat.com> References: <1f85dc8e6a0149677563a2dfb4cef9a9c7eaa391.1368702323.git.mst@redhat.com> <20130516184041.GP19669@dyad.programming.kicks-ass.net> <20130519093526.GD19883@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: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 982 Lines: 30 On Sun, 2013-05-19 at 12:35 +0300, Michael S. Tsirkin wrote: > No, I was not assuming that. What I'm trying to say is that a caller > that does something like this under a spinlock: > preempt_disable > pagefault_disable > error = copy_to_user > pagefault_enable > preempt_enable_no_resched > > is not doing anything wrong and should not get a warning, > as long as error is handled correctly later. > Right? > What I see wrong with the above is the preempt_enable_no_resched(). The only place that should be ever used is right before a schedule(), as you don't want to schedule twice (once for the preempt_enable() and then again for the schedule itself). Remember, in -rt, a spin lock does not disable preemption. -- 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/