From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752639AbaHXMLT (ORCPT ); Sun, 24 Aug 2014 08:11:19 -0400 Received: from a.ns.miles-group.at ([95.130.255.143]:65275 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752392AbaHXMLQ (ORCPT ); Sun, 24 Aug 2014 08:11:16 -0400 Message-ID: <53F9D661.8080100@nod.at> Date: Sun, 24 Aug 2014 14:11:13 +0200 From: Richard Weinberger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Thorsten Knabe CC: linux-kernel@vger.kernel.org, Thomas Meyer , Valdis.Kletnieks@vt.edu Subject: Re: [PATCH] UML: UBD: Fix for processes stuck in D state forever in UserModeLinux References: <53F89B7A.1040406@thorsten-knabe.de> <53F8B48D.8060209@nod.at> <53F8D2A7.70204@thorsten-knabe.de> In-Reply-To: <53F8D2A7.70204@thorsten-knabe.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 23.08.2014 19:43, schrieb Thorsten Knabe: > Hi Richard. > > On 08/23/2014 05:34 PM, Richard Weinberger wrote: >> Hi! >> >> Am 23.08.2014 15:47, schrieb Thorsten Knabe: >>> From: Thorsten Knabe >>> >>> UML: UBD: Fix for processes stuck in D state forever in UserModeLinux. >>> >>> Starting with Linux 3.12 processes get stuck in D state forever in >>> UserModeLinux under sync heavy workloads. This bug was introduced by >>> commit 805f11a0d5 (um: ubd: Add REQ_FLUSH suppport). >>> Fix bug by adding a check if FLUSH request was successfully submitted to >>> the I/O thread and keeping the FLUSH request on the request queue on >>> submission failures. >>> >>> Fixes: 805f11a0d5 (um: ubd: Add REQ_FLUSH suppport) >>> Signed-off-by: Thorsten Knabe >> >> Thanks a lot for hunting this issue down. >> >>> --- >>> Patch applies to 3.16.1. >>> >>> diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c >>> index 3716e69..b7d2840 100644 >>> --- a/arch/um/drivers/ubd_kern.c >>> +++ b/arch/um/drivers/ubd_kern.c >>> @@ -1277,7 +1277,7 @@ static void do_ubd_request(struct request_queue *q) >>> >>> while(1){ >>> struct ubd *dev = q->queuedata; >>> - if(dev->end_sg == 0){ >>> + if(dev->request == NULL){ >> >> Why do we need this specific change? > > This change is required, because for FLUSH requests dev->end_sg is > initialized to 0 by blk_rq_map_sg() a few lines above, as FLUSH requests > have no data blocks attached to themselves. You meant "below"? Looks like I really miss something here. At the bottom of the while(1) loop we have dev->end_sg = 0; dev->request = NULL; Thanks, //richard