From patchwork Thu Jun 30 17:20:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 587047 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 AF6A3C43334 for ; Thu, 30 Jun 2022 17:21:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236123AbiF3RVY (ORCPT ); Thu, 30 Jun 2022 13:21:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235638AbiF3RVX (ORCPT ); Thu, 30 Jun 2022 13:21:23 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 711621C13C for ; Thu, 30 Jun 2022 10:21:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1656609681; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=A5OgPBniuWt/Ivj7mlDLsvU3Ai/7R90RcZ3oxlYDH8I=; b=WwGs+UJ0uvD5noz/o3gl87YyEWay7DUltMdvI6kygGU1sei7vNRXCfzzoJSNXnpLft5F3m n+au0x9MHLi5NCrhvf45Wyt6adMUesfvrgjp8mBHa2lXFZzlPqn2Osg5IvXNWm/NBK6y8A qGzgGO9W83UjK1cggzcQl8icULT60zc= 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-647-pf0sS1ZOOiSK8jEHaUGHLQ-1; Thu, 30 Jun 2022 13:21:14 -0400 X-MC-Unique: pf0sS1ZOOiSK8jEHaUGHLQ-1 Received: by mail-wm1-f69.google.com with SMTP id k16-20020a7bc310000000b0038e6cf00439so1802383wmj.0 for ; Thu, 30 Jun 2022 10:21:14 -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:date:message-id:mime-version :content-transfer-encoding; bh=A5OgPBniuWt/Ivj7mlDLsvU3Ai/7R90RcZ3oxlYDH8I=; b=gVL33/v9Fnr4v86B5u48E64QBTH74v1ouqurbn/U++XYdzv6MojfaF9K+0vgULFS2h qanfTHO1Qy/n+23kVNW5rvcSPfbzUJH8DkU7Rxcd+423BqxkLoaul65d581JPuEVbGnM Fg1+lhTD5cpTGSMxj02SQyHBiMJF1JNcrUmEVl1aonoBZVJDYHy2x9TY31LpIlW8hXZQ Xj6Fk8ahuVCN3nxNS5APBuNeFmKeW6GAOpwmO472fajXiErUD7sYyRheuV6xvrPA0EIt 1IG71lVdKrWWmvFqKDjkLFOuIZcFGwUk9mRdeK9Ro+ieUXVVCRbjCksEZV02tsUn5/Hj PsWA== X-Gm-Message-State: AJIora+aRgBZAm7gkEGecVFGYqY5Y67OH/L3zY6mPtiq1m0EoXAonJ8y J3QenpxQqxITfRHB0/axMQLuWmRYycdB6a/VbggbAWgOL0X/SCnc/yrid7TRbrPkiCJeaDe54in VQnT2xUwIQc9HnyW+T/ITNR9Rpoc= X-Received: by 2002:a5d:448e:0:b0:21b:887f:23f with SMTP id j14-20020a5d448e000000b0021b887f023fmr9598762wrq.240.1656609673084; Thu, 30 Jun 2022 10:21:13 -0700 (PDT) X-Google-Smtp-Source: AGRyM1tLSw0n9SwkwRiHg02raa2UNgWCjcHEkLR9YfRZg33No2Yv3dNxwDSETN5lNlfJhNYkN9rmTg== X-Received: by 2002:a5d:448e:0:b0:21b:887f:23f with SMTP id j14-20020a5d448e000000b0021b887f023fmr9598740wrq.240.1656609672838; Thu, 30 Jun 2022 10:21:12 -0700 (PDT) Received: from vschneid.remote.csb ([185.11.37.247]) by smtp.gmail.com with ESMTPSA id f20-20020a05600c155400b0039c41686421sm4065122wmg.17.2022.06.30.10.21.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jun 2022 10:21:11 -0700 (PDT) From: Valentin Schneider To: kexec@lists.infradead.org, linux-rt-users@vger.kernel.org Cc: Eric Biederman , Arnd Bergmann , Petr Mladek , Miaohe Lin , Thomas Gleixner , Sebastian Andrzej Siewior , Juri Lelli , "Luis Claudio R. Goncalves" Subject: [PATCH v3 0/2] kexec, panic: Making crash_kexec() NMI safe Date: Thu, 30 Jun 2022 18:20:39 +0100 Message-Id: <20220630172041.4100123-1-vschneid@redhat.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org Hi folks, Here's v3 where we now completely get rid of kexec_mutex. o Patch 1 makes sure all kexec_mutex acquisitions are trylocks. This prevents having to add any while(atomic_cmpxchg()) loops which I'd really hate to see here. If that can't be done then I think we're better off with the combined mutex+atomic var approach. o Patch 2 does the mutex -> atomic var switch. Revisions ========= v2 -> v3 ++++++++ o Dropped kexec_mutex entirely and made the atomic variable the one true lock for kexec (Eric) v1 -> v2 ++++++++ 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 Cheers, Valentin Valentin Schneider (2): kexec: Turn all kexec_mutex acquisitions into trylocks panic, kexec: Make __crash_kexec() NMI safe include/linux/kexec.h | 2 +- kernel/kexec.c | 11 ++++------- kernel/kexec_core.c | 28 ++++++++++++++++------------ kernel/kexec_file.c | 4 ++-- kernel/kexec_internal.h | 15 ++++++++++++++- kernel/ksysfs.c | 7 ++++++- 6 files changed, 43 insertions(+), 24 deletions(-) --- 2.31.1