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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6086C433EF for ; Thu, 4 Nov 2021 15:54:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 864E060FE3 for ; Thu, 4 Nov 2021 15:54:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231593AbhKDP5a (ORCPT ); Thu, 4 Nov 2021 11:57:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231463AbhKDP52 (ORCPT ); Thu, 4 Nov 2021 11:57:28 -0400 Received: from mail-pl1-x633.google.com (mail-pl1-x633.google.com [IPv6:2607:f8b0:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D7EFC061714 for ; Thu, 4 Nov 2021 08:54:50 -0700 (PDT) Received: by mail-pl1-x633.google.com with SMTP id r5so7970621pls.1 for ; Thu, 04 Nov 2021 08:54:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:subject:to:cc:mime-version:message-id :content-transfer-encoding; bh=2mq5ANordmcrEkX0PoTEuQw2qzkrF/htgz2kP66qiS0=; b=RU4JohCg4W11vjiEq4qR3Jb4+dQbG5X+HdrecLh0R1CNnnTkezNEBvsSWCFur95WBx 1YYR+29GCrgC8TBzvttlbCwmqJ8qrlohG700ZddwWKVq+zB1u6YUixoUAU9nQ3crg7ad smqLLiSloMAwrGBNOfQ/ABSbBLTZqyvP6sDOme8Ja4RmVSN4v7afaHnzP6J7rU7RbdQl AwL3xZlnuh20UMi+0UYEYzvKAygty708LbTa1LZSOKTHuwBuJXzjZ8xaCChPeFkBSue8 lbs78+oaqDcnnetz3cUTaPhAqZIlqJOHpHbeWwdk7LG+YIVocK+f1X9GX67khS9GJe4b 44hg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:subject:to:cc:mime-version:message-id :content-transfer-encoding; bh=2mq5ANordmcrEkX0PoTEuQw2qzkrF/htgz2kP66qiS0=; b=GU7RVLTspbZWWV/aesEfm7PO65Oj/HR+GwESWFYUSY7FFQJFMv63lSEC+tqcDoB07R wSJOnEzEH5vYXp+zqOVWrBhetwnbhgUT+SAttWj6N7Pm41UJj7phxQhFEEt0hc/gMvBF u468KnQ5A1ozUXqqej/apYxGZZulE4Eq7ZTSu2JupwWrhSdvMuQRPPOuxD/A5Y6LmKdk C6gPYbgxcpcZCNH2zMfJyXeNsu/NHm7r9qYAiXr7ldEuOsY2a1p2yJBw9uMW7q3Hoes6 NFah9pYLIwsvxYMYGBmARU/Opj0S4iz3lDj2shYNsQ5+B/GxuGKktXFcO1x6FRnRAYvm Vl8Q== X-Gm-Message-State: AOAM532/DhsPp0nY3sR5FLhb7RvLOvnP+XHNEnmlzP5qlzDTAYjRutvE czgGnthpwEIp3hTFxzG8JPxHL7KojYo= X-Google-Smtp-Source: ABdhPJwzFDHHQAe6yHdh3UOvFCxsuJieeW7iaNzbH7/KXrFw5K4v+HOPz5CiXgRUVyXjnKpAZ7S8xg== X-Received: by 2002:a17:90b:1e44:: with SMTP id pi4mr2852548pjb.245.1636041289778; Thu, 04 Nov 2021 08:54:49 -0700 (PDT) Received: from localhost (60-241-46-56.tpgi.com.au. [60.241.46.56]) by smtp.gmail.com with ESMTPSA id c21sm5377284pfv.119.2021.11.04.08.54.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Nov 2021 08:54:49 -0700 (PDT) Date: Fri, 05 Nov 2021 01:54:44 +1000 From: Nicholas Piggin Subject: Removal of printk safe buffers delays NMI context printk To: John Ogness Cc: Petr Mladek , linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-Id: <1636039236.y415994wfa.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi John, It seems printk from NMI context is now delayed indefinitely and there is no printk_safe_flush equivalent (or I can't see one) to allow a NMI buffer to be flushed by a different CPU. This causes hard lockup watchdog messages to not get shown on the console. I can call printk from a different CPU and that seems to flush the stuck CPU's NMI buffer immediately. What's the best way to expose this? Can we have something like tihs? void printk_flush(void) { preempt_disable(); if (console_trylock_spinning()) console_unlock(); preempt_enable(); wake_up_klogd(); } Thanks, Nick