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=-2.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_MUTT 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 BFA1DC43381 for ; Wed, 20 Feb 2019 00:03:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7969921738 for ; Wed, 20 Feb 2019 00:03:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="EOL+ZWfG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729406AbfBTADg (ORCPT ); Tue, 19 Feb 2019 19:03:36 -0500 Received: from aserp2130.oracle.com ([141.146.126.79]:40852 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726405AbfBTADg (ORCPT ); Tue, 19 Feb 2019 19:03:36 -0500 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x1JNx1GW082842; Wed, 20 Feb 2019 00:02:26 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2018-07-02; bh=gfATYa55n+jW6sujzmXKFVyH/9xKyPiskuX1RgL782I=; b=EOL+ZWfG14CC1fIBhsKRlmFe+3jozjdbeuDOJ9Jan5dsfWb7hAj0T98SlddYlbTVe0dl 0+LHU/wgEpD+5fZPfRSS9cUyoUcYKfbG1dbEPl2WzFYGAiZRkUC85YlACzAp9jjfF8Fg mzkQ0Xg5LYm9sPYisAKElC+Y/bHjfZTxYOIQdL8SunhvixnYiQ7aIziYZFdqceUD56cH VixZvCMWR8/wASCKcwkje8MDL+KbQW1FWviXdwnxqpG4RVrGtBQKAFagZIZgchah5bPn yjnVcJZDecr57VwrxqjN4/H/wF+0Uw8/jZjnA9oOc50d+DEoeHGNWDZ0tMq8MIbuSXxA 3Q== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by aserp2130.oracle.com with ESMTP id 2qp81e6ptp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 Feb 2019 00:02:26 +0000 Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x1K02JUv001440 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 Feb 2019 00:02:19 GMT Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x1K02HXF029677; Wed, 20 Feb 2019 00:02:17 GMT Received: from localhost.localdomain (/108.49.136.197) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 19 Feb 2019 16:02:16 -0800 Date: Tue, 19 Feb 2019 19:02:10 -0500 From: Boris Ostrovsky To: Julien Grall Cc: Juergen Gross , Stefano Stabellini , xen-devel , "linux-kernel@vger.kernel.org" , Dave P Martin Subject: Re: xen/evtchn and forced threaded irq Message-ID: <20190220000209.GA4091@localhost.localdomain> References: <5e256d9a-572c-e01e-7706-407f99245b00@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5e256d9a-572c-e01e-7706-407f99245b00@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9172 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=946 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902190162 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 19, 2019 at 05:31:10PM +0000, Julien Grall wrote: > Hi all, > > I have been looking at using Linux RT in Dom0. Once the guest is started, > the console is ending to have a lot of warning (see trace below). > > After some investigation, this is because the irq handler will now be threaded. > I can reproduce the same error with the vanilla Linux when passing the option > 'threadirqs' on the command line (the trace below is from 5.0.0-rc7 that has > not RT support). > > FWIW, the interrupt for port 6 is used to for the guest to communicate with > xenstore. > > From my understanding, this is happening because the interrupt handler is now > run in a thread. So we can have the following happening. > > Interrupt context | Interrupt thread > | > receive interrupt port 6 | > clear the evtchn port | > set IRQF_RUNTHREAD | > kick interrupt thread | > | clear IRQF_RUNTHREAD > | call evtchn_interrupt > receive interrupt port 6 | > clear the evtchn port | > set IRQF_RUNTHREAD | > kick interrupt thread | > | disable interrupt port 6 > | evtchn->enabled = false > | [....] > | > | *** Handling the second interrupt *** > | clear IRQF_RUNTHREAD > | call evtchn_interrupt > | WARN(...) > > I am not entirely sure how to fix this. I have two solutions in mind: > > 1) Prevent the interrupt handler to be threaded. We would also need to > switch from spin_lock to raw_spin_lock as the former may sleep on RT-Linux. > > 2) Remove the warning I think access to evtchn->enabled is racy so (with or without the warning) we can't use it reliably. Another alternative could be to queue the irq if !evtchn->enabled and handle it in evtchn_write() (which is where irq is supposed to be re-enabled). -boris > > None of them are ideals. Do you have an opionion/better suggestion? > > [ 127.192087] Interrupt for port 6, but apparently not enabled; per-user 0000000078d39c7f > [ 127.200333] WARNING: CPU: 0 PID: 2553 at drivers/xen/evtchn.c:167 evtchn_interrupt+0xfc/0x120 > [ 127.208799] Modules linked in: > [ 127.211939] CPU: 0 PID: 2553 Comm: irq/52-evtchn:x Tainted: G W > 5.0.0-rc7-00023-g2a3d41623699 #1257 > [ 127.222374] Hardware name: ARM Juno development board (r2) (DT) > [ 127.228381] pstate: 40000005 (nZcv daif -PAN -UAO) > [ 127.233256] pc : evtchn_interrupt+0xfc/0x120 > [ 127.237607] lr : evtchn_interrupt+0xfc/0x120 > [ 127.241952] sp : ffff000012d2bd60 > [ 127.245347] x29: ffff000012d2bd60 x28: ffff00001015d608 > [ 127.250741] x27: ffff8008b39de400 x26: ffff00001015d330 > [ 127.256137] x25: ffff00001015d2d4 x24: 0000000000000001 > [ 127.261532] x23: ffff00001015d570 x22: 0000000000000034 > [ 127.266926] x21: 0000000000000000 x20: ffff8008b7f02400 > [ 127.272322] x19: ffff8008b3aba000 x18: 0000000000000037 > [ 127.277717] x17: 0000000000000000 x16: 0000000000000000 > [ 127.283112] x15: 00000000fffffff0 x14: 0000000000000000 > [ 127.288507] x13: 3030303030207265 x12: 000000000000000c > [ 127.293902] x11: ffff000010ea0a88 x10: 0000000000000000 > [ 127.299297] x9 : 00000000fffb9fff x8 : 0000000000000000 > [ 127.304701] x7 : 0000000000000001 x6 : ffff8008bac5c240 > [ 127.310087] x5 : ffff8008bac5c240 x4 : 0000000000000000 > [ 127.315483] x3 : ffff8008bac64708 x2 : ffff8008b39de400 > [ 127.320877] x1 : 893ac9b38837b800 x0 : 0000000000000000 > [ 127.326272] Call trace: > [ 127.328802] evtchn_interrupt+0xfc/0x120 > [ 127.332804] irq_forced_thread_fn+0x38/0x98 > [ 127.337066] irq_thread+0x190/0x238 > [ 127.340636] kthread+0x134/0x138 > [ 127.343942] ret_from_fork+0x10/0x1c > [ 127.347593] ---[ end trace 1d3fa385877cc18b ]--- > > > Cheers, > > -- > Julien Grall