Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933800AbcJTJe2 (ORCPT ); Thu, 20 Oct 2016 05:34:28 -0400 Received: from foss.arm.com ([217.140.101.70]:42066 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758503AbcJTJeY (ORCPT ); Thu, 20 Oct 2016 05:34:24 -0400 Date: Thu, 20 Oct 2016 10:33:53 +0100 From: Mark Rutland To: Ingo Molnar Cc: Andy Lutomirski , "linux-kernel@vger.kernel.org" , linux-arch , Andrew Morton , Heiko Carstens , "H. Peter Anvin" , Kees Cook , Andrew Lutomirski , Ingo Molnar , Thomas Gleixner Subject: Re: [PATCH 1/3] sched/core,x86: make struct thread_info arch specific again Message-ID: <20161020093353.GB10234@leverpostej> References: <1476901693-8492-1-git-send-email-mark.rutland@arm.com> <1476901693-8492-2-git-send-email-mark.rutland@arm.com> <20161020064045.GA29032@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161020064045.GA29032@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2128 Lines: 46 On Thu, Oct 20, 2016 at 08:40:45AM +0200, Ingo Molnar wrote: > > * Andy Lutomirski wrote: > > > On Wed, Oct 19, 2016 at 11:28 AM, Mark Rutland wrote: > > > From: Heiko Carstens > > > > > > commit c65eacbe290b ("sched/core: Allow putting thread_info into > > > task_struct") made struct thread_info a generic struct with only a > > > single flags member if THREAD_INFO_IN_TASK_STRUCT is selected. > > > > > > This change however seems to be quite x86 centric, since at least the > > > generic preemption code (asm-generic/preempt.h) assumes that struct > > > thread_info also has a preempt_count member, which apparently was not > > > true for x86. > > > > > > We could add a bit more ifdefs to solve this problem too, but it seems > > > to be much simpler to make struct thread_info arch specific > > > again. This also makes the conversion to THREAD_INFO_IN_TASK_STRUCT a > > > bit easier for architectures that have a couple of arch specific stuff > > > in their thread_info definition. > > > > > > The arch specific stuff _could_ be moved to thread_struct. However > > > keeping them in thread_info makes it easier: accessing thread_info > > > members is simple, since it is at the beginning of the task_struct, > > > while the thread_struct is at the end. At least on s390 the offsets > > > needed to access members of the thread_struct (with task_struct as > > > base) are too large for various asm instructions. This is not a > > > problem when keeping these members within thread_info. > > > > Acked-by: Andy Lutomirski > > > > Ingo, there's a (somewhat weak) argument for sending this via > > tip/urgent: it doesn't change generated code at all, and I think it > > will avoid a silly depedency or possible conflict for the next merge > > window, since both arm64 and s390 are going to need it. > > Can certainly do it if this is the final version of the patch. Mark? Yes; this is the final version of this patch. I can rebase the other two core patches atop, assuming this goes in for a v4.9-rc* tag soon. Thanks, Mark.