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 BE28FC0032E for ; Wed, 25 Oct 2023 19:51:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234633AbjJYTv5 (ORCPT ); Wed, 25 Oct 2023 15:51:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33978 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233176AbjJYTvv (ORCPT ); Wed, 25 Oct 2023 15:51:51 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:242:246e::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B7B5E193 for ; Wed, 25 Oct 2023 12:51:49 -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=rBV0nSZdE0vCEbKk3Yf9TUFnrefWidkNWcmqpKnwJq8=; t=1698263509; x=1699473109; b=HCCUHbSltL3OT0rl8giUu60iZYafzHPm/DrNFIq0/qSEbhx XMtFmphDfC0ntsWqnK80KkBLt78AeegHV8y5ebsv/JpV+mJ6fLKI1ZZKPxO/vNSO8uDfJNGukn+iL z+yF8z5m1K6NB1FxlL03xW/gCzzwaGcJwsUd8dr3EhJXT4mnzM7OEo4ga12IwxhHEyqiU+LH2DpUy Jl/pRLD93KiqoOoP1iin5Ub+3GDU+vFq8wFzfk4htGn7/94PO0u9iffPOzZ4zzoZ3uOXyKEmliro8 FVoP/IwdZ3LvP2nbrSAEpse03x3fEXBnMjWPTnXzjjotw//ZLEKlvxrdF9U6gbOQ==; 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 1qvjus-00000002hQU-1l3m; Wed, 25 Oct 2023 21:51:46 +0200 Message-ID: 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 21:51:45 +0200 In-Reply-To: References: <20231020-uml-time-backwards-v1-1-90b776fc6dfd@axis.com> <4a75c40636be267163dc30b5a6a2442089628e57.camel@axis.com> <4dbed8896c94a347dcb58b3a83792c52fdc1c04a.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 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 reproducible > without that by using the attached config and the following program as > 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 > With the above commands I usually see the panic in a few seconds. This > is on an unmodified v6.6-rc7. >=20 Yes, I can reproduce it with your test, thanks. I'm on 6.4-rc still for $reasons (6.5 we skipped during vacations, and 6.6 EEVDF scheduler broke everything for hwsim tests in hostap), but this code didn't really change anyway. I'll poke at this. (And I'm still amazed that anyone other than me even uses this stuff :P) johannes