From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e06smtp17.uk.ibm.com (e06smtp17.uk.ibm.com [195.75.94.113]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 5613F1A0994 for ; Fri, 28 Nov 2014 02:19:16 +1100 (AEDT) Received: from /spool/local by e06smtp17.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 27 Nov 2014 15:19:12 -0000 Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by d06dlp03.portsmouth.uk.ibm.com (Postfix) with ESMTP id C160A1B08061 for ; Thu, 27 Nov 2014 15:19:23 +0000 (GMT) Received: from d06av11.portsmouth.uk.ibm.com (d06av11.portsmouth.uk.ibm.com [9.149.37.252]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id sARFJ8wT14549058 for ; Thu, 27 Nov 2014 15:19:08 GMT Received: from d06av11.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av11.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id sARFJ79u024184 for ; Thu, 27 Nov 2014 08:19:08 -0700 Date: Thu, 27 Nov 2014 16:19:05 +0100 From: David Hildenbrand To: Thomas Gleixner Subject: Re: [RFC 0/2] Reenable might_sleep() checks for might_fault() when atomic Message-ID: <20141127161905.7c6220ee@thinkpad-w530> In-Reply-To: References: <20141126151729.GB9612@redhat.com> <20141126152334.GA9648@redhat.com> <20141126163207.63810fcb@thinkpad-w530> <20141126154717.GB10568@redhat.com> <5475FAB1.1000802@de.ibm.com> <20141126163216.GB10850@redhat.com> <547604FC.4030300@de.ibm.com> <20141126170447.GC11202@redhat.com> <20141127070919.GA4390@osiris> <20141127090301.3ddc3077@thinkpad-w530> <20141127120441.GB4390@osiris> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: linux-arch@vger.kernel.org, "Michael S. Tsirkin" , Heiko Carstens , linux-kernel@vger.kernel.org, Christian Borntraeger , paulus@samba.org, schwidefsky@de.ibm.com, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, mingo@kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , > OTOH, there is no reason why we need to disable preemption over that > page_fault_disabled() region. There are code pathes which really do > not require to disable preemption for that. > > We have that seperated in preempt-rt for obvious reasons and IIRC > Peter Zijlstra tried to distangle it in mainline some time ago. I > forgot why that never got merged. > Of course, we can completely separate that in our page fault code by doing pagefault_disabled() checks instead of in_atomic() checks (even in add on patches later). > We tie way too much stuff on the preemption count already, which is a > mightmare because we have no clear distinction of protection > scopes. Although it might not be optimal, but keeping a separate counter for pagefault_disable() as part of the preemption counter seems to be the only doable thing right now. I am not sure if a completely separated counter is even possible, increasing the size of thread_info. I am working on a prototype right now. Thanks! > > Thanks, > > tglx >