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 A2055C43334 for ; Thu, 23 Jun 2022 11:40:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230447AbiFWLkH (ORCPT ); Thu, 23 Jun 2022 07:40:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230349AbiFWLkG (ORCPT ); Thu, 23 Jun 2022 07:40:06 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id F36594BFD6 for ; Thu, 23 Jun 2022 04:40:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1655984404; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pXX1Tci8u6uSkWlCeJ6TegtPSfgMP3wYaXXEz0pOrgM=; b=OaZVVip9LN/4AoDZryX9HsRC1xmCNjwx1AvQoBJZKv+ztF/kGJ9W703UZl9bMq3i0F1iiA ty1prNpcnCWCURujDjSvGbxxaFWlNcILTo9RIrUW6ATHn71i2kXPVcBGrq1iYSB2hpkwsZ sqzsqpMRmUkiircDI9dI51cZUwIzAqY= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-298-upTb53_9P9SB-ChKbmpmgA-1; Thu, 23 Jun 2022 07:40:00 -0400 X-MC-Unique: upTb53_9P9SB-ChKbmpmgA-1 Received: by mail-wm1-f69.google.com with SMTP id p6-20020a05600c358600b0039c873184b9so1302533wmq.4 for ; Thu, 23 Jun 2022 04:40:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version:content-transfer-encoding; bh=pXX1Tci8u6uSkWlCeJ6TegtPSfgMP3wYaXXEz0pOrgM=; b=DKS3p6qBOb5bzZ66kWfgJXQZXH8lmoxLhBBr1gUnIFmUv7ts3ApYDUdsYSl30o7M/b L8Gr4Z+1eYzHCoECr7bnJklNiu8GFsyg4yME8egsj2Ee7ogfHun9FWTKodUDoT+UhZBc S5vFlbzjIjGNh3rqafcMniYLxWloGaKLYPgciqYWxlJVVsztnhuyktMXU2R/HLq32uba J+LlfMEFQHy1jHkh5Fy2exxKZA3XXRIeaT82rF80HW+CzKgItQpfK/sxM/Y7xiqT8DIj 5CspbS5RnEb+3cwCIZAfxHEBZ9WaWQPR99z9psXk4MIfL35ounyU+Z8j3iv/lpeb3UL9 hyFw== X-Gm-Message-State: AJIora/UeTSEmADJEbPNT0Lw+jnYXOI7AuCJPs6e/1UTvTYrx/hiuWhG dIVwvzyvQ/ZGYn4YHs1UpCJ3/TXTdCUEqfSN21sd8lg/gMbkMwYtYg5VrKafvlynP7SgmFW2nLl 0wbOgjgSfoiDUZtHI55I3/joR X-Received: by 2002:adf:dece:0:b0:21b:a4b0:f7e3 with SMTP id i14-20020adfdece000000b0021ba4b0f7e3mr4817782wrn.197.1655984399533; Thu, 23 Jun 2022 04:39:59 -0700 (PDT) X-Google-Smtp-Source: AGRyM1sK/dnm6ZYIya+uSaMaOutOXp1zODWOwg9uNXRImx0f7YrOK+SdjBXJeYaIC5fXn2ZDefBv4A== X-Received: by 2002:adf:dece:0:b0:21b:a4b0:f7e3 with SMTP id i14-20020adfdece000000b0021ba4b0f7e3mr4817761wrn.197.1655984399335; Thu, 23 Jun 2022 04:39:59 -0700 (PDT) Received: from vschneid.remote.csb ([185.11.37.247]) by smtp.gmail.com with ESMTPSA id h30-20020adfaa9e000000b0020c7ec0fdf4sm27013707wrc.117.2022.06.23.04.39.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jun 2022 04:39:58 -0700 (PDT) From: Valentin Schneider To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-rt-users@vger.kernel.org, Eric Biederman , Arnd Bergmann , Petr Mladek , Thomas Gleixner , Juri Lelli , "Luis Claudio R. Goncalves" Subject: Re: [PATCH v2] panic, kexec: Make __crash_kexec() NMI safe In-Reply-To: References: <20220620111520.1039685-1-vschneid@redhat.com> Date: Thu, 23 Jun 2022 12:39:57 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/06/22 11:31, Sebastian Andrzej Siewior wrote: > On 2022-06-20 12:15:20 [+0100], Valentin Schneider wrote: >> Attempting to get a crash dump out of a debug PREEMPT_RT kernel via an N= MI >> panic() doesn't work. The cause of that lies in the PREEMPT_RT definition >> of mutex_trylock(): >>=20 > =E2=80=A6 > >> Fixes: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softi= rq context") >> Signed-off-by: Valentin Schneider > > Reviewed-by: Sebastian Andrzej Siewior > >> --- >> v1 -> v2 >> ++++++++ >>=20 >> o Changed from Peterson-like synchronization to simpler atomic_cmpxchg >> (Petr) >> o Slightly reworded changelog >> o Added Fixes: tag. Technically should be up to since kexec can happen >> in an NMI, but that isn't such a clear target > > RT-wise it would be needed for each release. So git tells me the Fixes: commit dates from v4.2; from [1] and [2] I get that both current longterm stable and stable-rt trees go as far back as v4.9, so I'm guessing if that gets picked up for the stable trees then it should make its way into the stable -rt trees? [1]: https://wiki.linuxfoundation.org/realtime/preempt_rt_versions [2]: https://www.kernel.org/category/releases.html > There is also a mutex_unlock() in case an image is missing. This can go > via the scheduler if there is a waiter which does not look good with the > NMI in the picture. > > Sebastian