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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BCB7DC0032E for ; Wed, 25 Oct 2023 20:41:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229975AbjJYUlp (ORCPT ); Wed, 25 Oct 2023 16:41:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45192 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229576AbjJYUlo (ORCPT ); Wed, 25 Oct 2023 16:41:44 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:242:246e::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B536123 for ; Wed, 25 Oct 2023 13:41:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sipsolutions.net; s=mail; h=MIME-Version:Content-Transfer-Encoding: Content-Type:References:In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-To: Resent-Cc:Resent-Message-ID; bh=DsYdjSLqGrd7t0Y6Nn+QoZo/dHfV0hHOlcoK0gUrZCY=; t=1698266502; x=1699476102; b=VbXcNBxExPBtHf41XOudPWdtvXioFtTbThO3Nc6+gwCmbjg UbW/3yb6LZgWl6IEXuqM5nwjYaNIToem4HfsAuJHCPoYL0ws7eRYEtYSWbE0DvpjagRHpwWpBB14m SPfOnqmVXyp3Wz/ph1XG94/ykrQjmsJxNq4JQasdBMAAfOZB92sQS18c+V18ghU+zURa9NyG3SVED CSBr0u8paG0c23/kS53aUDB7KJIQm1mTh+BUcHRGIY3ThR+k5pQibeYhED2hbrP7eZWPY3H/ifhPY NLJXHnwgVm3waiPdv29jaCeM4A7bz8oVWiexehS1cwO5uOptdMVeO37K11IiUZuw==; Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.97-RC1) (envelope-from ) id 1qvkh9-00000002iVb-0Mrm; Wed, 25 Oct 2023 22:41:39 +0200 Message-ID: <1f38d92435cc4f3a5e8d17dff3da9e34be2e6f24.camel@sipsolutions.net> Subject: Re: [PATCH] um: time-travel: fix time going backwards From: Johannes Berg To: Vincent Whitchurch , "anton.ivanov@cambridgegreys.com" , "richard@nod.at" Cc: "linux-um@lists.infradead.org" , "linux-kernel@vger.kernel.org" , kernel Date: Wed, 25 Oct 2023 22:41:38 +0200 In-Reply-To: <68b18065d8be905c25522bd3f5a9b46dbe3a976d.camel@sipsolutions.net> References: <20231020-uml-time-backwards-v1-1-90b776fc6dfd@axis.com> <4a75c40636be267163dc30b5a6a2442089628e57.camel@axis.com> <4dbed8896c94a347dcb58b3a83792c52fdc1c04a.camel@sipsolutions.net> <68b18065d8be905c25522bd3f5a9b46dbe3a976d.camel@sipsolutions.net> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.48.4 (3.48.4-1.fc38) MIME-Version: 1.0 X-malware-bazaar: not-scanned Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2023-10-25 at 22:02 +0200, Johannes Berg wrote: > On Wed, 2023-10-25 at 21:51 +0200, Johannes Berg wrote: > > On Wed, 2023-10-25 at 11:55 +0000, Vincent Whitchurch wrote: > > > On Mon, 2023-10-23 at 09:33 +0200, Johannes Berg wrote: > > > > Do you have a specific workload that tends to reproduce this? > > >=20 > > > I've been seeing it when running roadtest, but it's easily reproducib= le > > > without that by using the attached config and the following program a= s > > > init. > > >=20 > > > cp repro.config .config > > > make ARCH=3Dum olddefconfig all > > > gcc -Wall -static -o repro repro.c > > > ./linux time-travel init=3D$PWD/repro rootfstype=3Dhostfs >=20 > Ohhh. >=20 > Pure "time-travel" is actually something I hardly think about these > days, we mostly use time-travel=3Dinf-cpu (or =3Dext). >=20 > That makes sense, here you actually *can* get interrupted. I'll need to > dig into what happens though. I just sent a patch, please take a look. It does seem to fix it - at least I got bored of waiting after running your test program for a few minutes :) johannes