From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B82E2C43387 for ; Wed, 9 Jan 2019 00:39:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7FA8E20661 for ; Wed, 9 Jan 2019 00:39:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729021AbfAIAjS (ORCPT ); Tue, 8 Jan 2019 19:39:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58328 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727829AbfAIAjS (ORCPT ); Tue, 8 Jan 2019 19:39:18 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0D3F05AF9E; Wed, 9 Jan 2019 00:39:18 +0000 (UTC) Received: from ovpn-120-48.rdu2.redhat.com (ovpn-120-48.rdu2.redhat.com [10.10.120.48]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4364A5D76A; Wed, 9 Jan 2019 00:39:15 +0000 (UTC) Message-ID: <1546994355.3632.15.camel@redhat.com> Subject: Re: [PATCH RT] x86/mm/pat: disable preemption __split_large_page() after spin_lock() From: Scott Wood To: Sebastian Andrzej Siewior , linux-rt-users@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Steven Rostedt , stable-rt@vger.kernel.org Date: Tue, 08 Jan 2019 18:39:15 -0600 In-Reply-To: <20181213164430.mggilzfjgr5retz6@linutronix.de> References: <20181213164430.mggilzfjgr5retz6@linutronix.de> Organization: Red Hat Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 09 Jan 2019 00:39:18 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2018-12-13 at 17:44 +0100, Sebastian Andrzej Siewior wrote: > Commit "x86/mm/pat: Disable preemption around __flush_tlb_all()" added a > warning if __flush_tlb_all() is invoked in preemptible context. On !RT > the warning does not trigger because a spin lock is acquired which > disables preemption. On RT the spin lock does not disable preemption and > so the warning is seen. > > Disable preemption to avoid the warning in __flush_tlb_all(). > > Signed-off-by: Sebastian Andrzej Siewior FWIW, that __flush_tlb_all() can probably just be removed. It was added as a partial workaround for an erratum, but since it didn't completely solve the problem, hugepages were disabled on the affected chips in commit 7a0fc404ae66377 ("x86: Disable large pages on CPUs with Atom erratum AAE44"). I was going to send a (non-RT) patch removing the flush but in 4.20 commit c0a759abf5a68 ("x86/mm/cpa: Move flush_tlb_all()") reworked the code to make it moot. -Scott