From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id 9CDFD6B006E for ; Thu, 7 May 2015 07:51:46 -0400 (EDT) Received: by pacwv17 with SMTP id wv17so38326917pac.0 for ; Thu, 07 May 2015 04:51:46 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org. [2001:1868:205::9]) by mx.google.com with ESMTPS id j9si2511845pdl.24.2015.05.07.04.51.45 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 07 May 2015 04:51:45 -0700 (PDT) Date: Thu, 7 May 2015 13:51:18 +0200 From: Peter Zijlstra Subject: Re: [PATCH RFC 01/15] uaccess: count pagefault_disable() levels in pagefault_disabled Message-ID: <20150507115118.GT21418@twins.programming.kicks-ass.net> References: <1430934639-2131-1-git-send-email-dahi@linux.vnet.ibm.com> <1430934639-2131-2-git-send-email-dahi@linux.vnet.ibm.com> <20150507102254.GE23123@twins.programming.kicks-ass.net> <20150507125053.5d2e8f0a@thinkpad-w530> <20150507111231.GF23123@twins.programming.kicks-ass.net> <20150507134030.137deeb2@thinkpad-w530> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150507134030.137deeb2@thinkpad-w530> Sender: owner-linux-mm@kvack.org List-ID: To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, yang.shi@windriver.com, bigeasy@linutronix.de, benh@kernel.crashing.org, paulus@samba.org, akpm@linux-foundation.org, heiko.carstens@de.ibm.com, schwidefsky@de.ibm.com, borntraeger@de.ibm.com, mst@redhat.com, tglx@linutronix.de, David.Laight@ACULAB.COM, hughd@google.com, hocko@suse.cz, ralf@linux-mips.org, herbert@gondor.apana.org.au, linux@arm.linux.org.uk, airlied@linux.ie, daniel.vetter@intel.com, linux-mm@kvack.org, linux-arch@vger.kernel.org On Thu, May 07, 2015 at 01:40:30PM +0200, David Hildenbrand wrote: > But anyhow, opinions seem to differ how to best handle that whole stuff. > > I think a separate counter just makes sense, as we are dealing with two > different concepts and we don't want to lose the preempt_disable =^ NOP > for !CONFIG_PREEMPT. > > I also think that > > pagefault_disable() > rt = copy_from_user() > pagefault_enable() > > is a valid use case. > > So any suggestions how to continue? static inline bool __pagefault_disabled(void) { return current->pagefault_disabled; } static inline bool pagefault_disabled(void) { return in_atomic() || __pagefault_disabled(); } And leave the preempt_disable() + pagefault_disable() for now. You're right in that that is clearest. If we ever get to the point where that really is an issue, I'll try and be clever then :-) -- 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