From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f45.google.com (mail-wg0-f45.google.com [74.125.82.45]) by kanga.kvack.org (Postfix) with ESMTP id 4A36D6B0038 for ; Thu, 7 May 2015 06:23:20 -0400 (EDT) Received: by wgiu9 with SMTP id u9so38676676wgi.3 for ; Thu, 07 May 2015 03:23:19 -0700 (PDT) Received: from casper.infradead.org (casper.infradead.org. [2001:770:15f::2]) by mx.google.com with ESMTPS id tb3si3074871wic.122.2015.05.07.03.23.18 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 07 May 2015 03:23:18 -0700 (PDT) Date: Thu, 7 May 2015 12:22:54 +0200 From: Peter Zijlstra Subject: Re: [PATCH RFC 01/15] uaccess: count pagefault_disable() levels in pagefault_disabled Message-ID: <20150507102254.GE23123@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1430934639-2131-2-git-send-email-dahi@linux.vnet.ibm.com> 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 Wed, May 06, 2015 at 07:50:25PM +0200, David Hildenbrand wrote: > +/* > + * Is the pagefault handler disabled? If so, user access methods will not sleep. > + */ > +#define pagefault_disabled() (current->pagefault_disabled != 0) So -RT has: static inline bool pagefault_disabled(void) { return current->pagefault_disabled || in_atomic(); } AFAICR we did this to avoid having to do both: preempt_disable(); pagefault_disable(); in a fair number of places -- just like this patch-set does, this is touching two cachelines where one would have been enough. Also, removing in_atomic() from fault handlers like you did significantly changes semantics for interrupts (soft, hard and NMI). So while I agree with most of these patches, I'm very hesitant on the above little detail. -- 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