From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752701Ab3ESNfs (ORCPT ); Sun, 19 May 2013 09:35:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10092 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751381Ab3ESNfq (ORCPT ); Sun, 19 May 2013 09:35:46 -0400 Date: Sun, 19 May 2013 16:34:18 +0300 From: "Michael S. Tsirkin" To: Steven Rostedt 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 Subject: Re: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep Message-ID: <20130519133418.GA24381@redhat.com> References: <1f85dc8e6a0149677563a2dfb4cef9a9c7eaa391.1368702323.git.mst@redhat.com> <20130516184041.GP19669@dyad.programming.kicks-ass.net> <20130519093526.GD19883@redhat.com> <1368966844.6828.111.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1368966844.6828.111.camel@gandalf.local.home> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 19, 2013 at 08:34:04AM -0400, Steven Rostedt wrote: > 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 Right but we need to keep it working on upstream as well. If I do preempt_enable under a spinlock upstream won't it try to sleep under spinlock? -- MST From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep Date: Sun, 19 May 2013 16:34:18 +0300 Message-ID: <20130519133418.GA24381@redhat.com> References: <1f85dc8e6a0149677563a2dfb4cef9a9c7eaa391.1368702323.git.mst@redhat.com> <20130516184041.GP19669@dyad.programming.kicks-ass.net> <20130519093526.GD19883@redhat.com> <1368966844.6828.111.camel@gandalf.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1368966844.6828.111.camel@gandalf.local.home> Sender: owner-linux-mm@kvack.org To: Steven Rostedt 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@vg List-Id: linux-arch.vger.kernel.org On Sun, May 19, 2013 at 08:34:04AM -0400, Steven Rostedt wrote: > 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 Right but we need to keep it working on upstream as well. If I do preempt_enable under a spinlock upstream won't it try to sleep under spinlock? -- MST -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx137.postini.com [74.125.245.137]) by kanga.kvack.org (Postfix) with SMTP id 857236B0002 for ; Sun, 19 May 2013 09:34:54 -0400 (EDT) Date: Sun, 19 May 2013 16:34:18 +0300 From: "Michael S. Tsirkin" Subject: Re: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep Message-ID: <20130519133418.GA24381@redhat.com> References: <1f85dc8e6a0149677563a2dfb4cef9a9c7eaa391.1368702323.git.mst@redhat.com> <20130516184041.GP19669@dyad.programming.kicks-ass.net> <20130519093526.GD19883@redhat.com> <1368966844.6828.111.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1368966844.6828.111.camel@gandalf.local.home> Sender: owner-linux-mm@kvack.org List-ID: To: Steven Rostedt 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 On Sun, May 19, 2013 at 08:34:04AM -0400, Steven Rostedt wrote: > 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 Right but we need to keep it working on upstream as well. If I do preempt_enable under a spinlock upstream won't it try to sleep under spinlock? -- MST -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by ozlabs.org (Postfix) with ESMTP id 9C5DE2C008D for ; Sun, 19 May 2013 23:35:32 +1000 (EST) Date: Sun, 19 May 2013 16:34:18 +0300 From: "Michael S. Tsirkin" To: Steven Rostedt Subject: Re: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep Message-ID: <20130519133418.GA24381@redhat.com> References: <1f85dc8e6a0149677563a2dfb4cef9a9c7eaa391.1368702323.git.mst@redhat.com> <20130516184041.GP19669@dyad.programming.kicks-ass.net> <20130519093526.GD19883@redhat.com> <1368966844.6828.111.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1368966844.6828.111.camel@gandalf.local.home> Cc: linux-m32r-ja@ml.linux-m32r.org, kvm@vger.kernel.org, Peter Zijlstra , Catalin Marinas , Will Deacon , David Howells , linux-mm@kvack.org, Paul Mackerras , "H. Peter Anvin" , linux-arch@vger.kernel.org, linux-am33-list@redhat.com, Hirokazu Takata , x86@kernel.org, Ingo Molnar , Arnd Bergmann , microblaze-uclinux@itee.uq.edu.au, Chris Metcalf , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Michal Simek , linux-m32r@ml.linux-m32r.org, linux-kernel@vger.kernel.org, Koichi Yasutake , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sun, May 19, 2013 at 08:34:04AM -0400, Steven Rostedt wrote: > 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 Right but we need to keep it working on upstream as well. If I do preempt_enable under a spinlock upstream won't it try to sleep under spinlock? -- MST From mboxrd@z Thu Jan 1 00:00:00 1970 From: mst@redhat.com (Michael S. Tsirkin) Date: Sun, 19 May 2013 16:34:18 +0300 Subject: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep In-Reply-To: <1368966844.6828.111.camel@gandalf.local.home> References: <1f85dc8e6a0149677563a2dfb4cef9a9c7eaa391.1368702323.git.mst@redhat.com> <20130516184041.GP19669@dyad.programming.kicks-ass.net> <20130519093526.GD19883@redhat.com> <1368966844.6828.111.camel@gandalf.local.home> Message-ID: <20130519133418.GA24381@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sun, May 19, 2013 at 08:34:04AM -0400, Steven Rostedt wrote: > 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 Right but we need to keep it working on upstream as well. If I do preempt_enable under a spinlock upstream won't it try to sleep under spinlock? -- MST