From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx157.postini.com [74.125.245.157]) by kanga.kvack.org (Postfix) with SMTP id E9BFB6B0002 for ; Sun, 19 May 2013 12:06:23 -0400 (EDT) Message-ID: <1368979579.6828.114.camel@gandalf.local.home> Subject: Re: [PATCH v2 10/10] kernel: might_fault does not imply might_sleep From: Steven Rostedt Date: Sun, 19 May 2013 12:06:19 -0400 In-Reply-To: <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> <20130519133418.GA24381@redhat.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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 On Sun, 2013-05-19 at 16:34 +0300, Michael S. Tsirkin wrote: > 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? No it wont. A spinlock calls preempt_disable implicitly, and a preempt_enable() will not schedule unless preempt_count is zero, which it wont be under a spinlock. If it did, there would be lots of bugs all over the place because this is done throughout the kernel (a preempt_enable() under a spinlock). In other words, don't ever use preempt_enable_no_resched(). -- Steve -- 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