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=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 37ACBC34047 for ; Wed, 19 Feb 2020 14:53:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0B83E206ED for ; Wed, 19 Feb 2020 14:53:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726784AbgBSOxV convert rfc822-to-8bit (ORCPT ); Wed, 19 Feb 2020 09:53:21 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:38431 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726582AbgBSOxU (ORCPT ); Wed, 19 Feb 2020 09:53:20 -0500 Received: from [5.158.153.52] (helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1j4Qiu-00063u-0H; Wed, 19 Feb 2020 15:53:12 +0100 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 9D842103A05; Wed, 19 Feb 2020 15:53:11 +0100 (CET) From: Thomas Gleixner To: =?utf-8?B?SsO8cmdlbiBHcm/Dnw==?= , LKML Cc: x86@kernel.org, Boris Ostrovsky , Stefano Stabellini , xen-devel@lists.xenproject.org Subject: Re: [PATCH] xen: Enable interrupts when calling _cond_resched() In-Reply-To: <8808612b-11c2-f7b8-f027-7ff92e992c50@suse.com> References: <87tv3mq1rm.fsf@nanos.tec.linutronix.de> <8808612b-11c2-f7b8-f027-7ff92e992c50@suse.com> Date: Wed, 19 Feb 2020 15:53:11 +0100 Message-ID: <87h7zmpr1k.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jürgen Groß writes: > On 19.02.20 12:01, Thomas Gleixner wrote: >> xen_maybe_preempt_hcall() is called from the exception entry point >> xen_do_hypervisor_callback with interrupts disabled. >> >> _cond_resched() evades the might_sleep() check in cond_resched() which >> would have caught that and schedule_debug() unfortunately lacks a check >> for irqs_disabled(). >> >> Enable interrupts around the call and use cond_resched() to catch future >> issues. >> >> Fixes: fdfd811ddde3 ("x86/xen: allow privcmd hypercalls to be preempted") >> Signed-off-by: Thomas Gleixner >> --- >> drivers/xen/preempt.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> --- a/drivers/xen/preempt.c >> +++ b/drivers/xen/preempt.c >> @@ -33,8 +33,10 @@ asmlinkage __visible void xen_maybe_pree >> * cpu. >> */ >> __this_cpu_write(xen_in_preemptible_hcall, false); >> - _cond_resched(); >> + local_irq_enable(); >> + cond_resched(); >> __this_cpu_write(xen_in_preemptible_hcall, true); >> + local_irq_disable(); > > Could you please put the call of local_irq_disable() directly after the > cond_resched() call to make the result symmetric regarding writing of > xen_in_preemptible_hcall and irq enable/disable? Darn. Of course does this need to be there. Stupid me, let me resend.