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 X-Spam-Level: X-Spam-Status: No, score=-9.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00154C433DF for ; Fri, 22 May 2020 10:03:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C29FF20738 for ; Fri, 22 May 2020 10:03:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="AozOV1Jv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728416AbgEVKDS (ORCPT ); Fri, 22 May 2020 06:03:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40550 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726578AbgEVKDR (ORCPT ); Fri, 22 May 2020 06:03:17 -0400 Received: from mail-pf1-x444.google.com (mail-pf1-x444.google.com [IPv6:2607:f8b0:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 64FBAC061A0E for ; Fri, 22 May 2020 03:03:17 -0700 (PDT) Received: by mail-pf1-x444.google.com with SMTP id 145so4982786pfw.13 for ; Fri, 22 May 2020 03:03:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id; bh=/Ly0FZ1XMvk/0WTHXshwlxj04l0m432nKVvBo4F3A6Q=; b=AozOV1JvUkbhSli/GuwvCZa+TcZ2IVZW1h1ssIA+PsgfpglluQQOZyPjlOzzguMWyt qKjOTrvJSjIwuwc53yi0bU83bMhGeDPTu7OPi5IUa/mZcOZDWLRi72u0U7Why35oq8Of gznlIWX0Poi4kVv1LZCO1+hbV+fGb+u6aDIpxk4ZwpBHFo3mBigaw8CtlHIInY5eXCzt +H2DhMWFVifQoptuWS4EPdDZS6kGG494BoEqxi+G9uFr5gH+FbAnCE1f5Id0SGmuArl4 gAKuPyvy4IJr526ZgQmSGvo+Ywa25xEooqiPJFdQWwF0xmds3OYo5MU2Hhot5/t6FJ4C anxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=/Ly0FZ1XMvk/0WTHXshwlxj04l0m432nKVvBo4F3A6Q=; b=cDebtD0XVNn+WrE4sIGzrguQO8BO4om2nNkV1KKnDCXI3zL4FddB4cMf8NAShyw3m7 EgoY5PQt35/TDIn+yhTAmpGFkNMoXKIwgfQF58gk1oQd7CMSNzEiwpNt8CRjSrI4Z1Q8 bPjX+yhzA0Ruw0hsfWahLDq/cQcLmz7QcRgFLKoPpUw4wfIkySgm1K4hDHmpeLWLo8EA p/uYhRRSKwzDrcLcAbJ1p8DIfXYEB1guvhlIf4f7MHgnNdhp2wKjW1IsS38KlbJ8FKbM YCHiQf+wbftoF6Y9F4me0bnkHnCCWRVC7hVrXeDb3qIzes0odrFXmIxzglIf6orqdqeY Oyog== X-Gm-Message-State: AOAM533qd+D0On6OH00EMpamGqSAQsfv6trnT5dSMepSaIkSZDCUceak MJJSWvXSi+bTXF6+YqqE9hsuuA== X-Google-Smtp-Source: ABdhPJwWr2TfnrurtMH4xVDrw2CfDB32Bc5E8x2mOS8SX+3DgkeMHiuUcbAQx3t3cBf4wEFfwnvuug== X-Received: by 2002:aa7:9297:: with SMTP id j23mr3099183pfa.15.1590141796773; Fri, 22 May 2020 03:03:16 -0700 (PDT) Received: from localhost.localdomain ([117.252.68.136]) by smtp.gmail.com with ESMTPSA id c24sm6477633pfp.186.2020.05.22.03.03.11 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 May 2020 03:03:15 -0700 (PDT) From: Sumit Garg To: kgdb-bugreport@lists.sourceforge.net Cc: jason.wessel@windriver.com, daniel.thompson@linaro.org, dianders@chromium.org, pmladek@suse.com, sergey.senozhatsky@gmail.com, linux-kernel@vger.kernel.org, Sumit Garg Subject: [PATCH] kdb: Make kdb_printf robust to run in NMI context Date: Fri, 22 May 2020 15:32:26 +0530 Message-Id: <1590141746-23559-1-git-send-email-sumit.garg@linaro.org> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While rounding up CPUs via NMIs, its possible that a rounded up CPU maybe holding a console port lock leading to kgdb master CPU stuck in a deadlock during invocation of console write operations. So in order to avoid such a deadlock, invoke bust_spinlocks() prior to invocation of console handlers. Also, add a check for console port to be enabled prior to invocation of corresponding handler. Suggested-by: Petr Mladek Suggested-by: Sergey Senozhatsky Signed-off-by: Sumit Garg --- kernel/debug/kdb/kdb_io.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 924bc92..e32ece6 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -699,7 +699,11 @@ int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap) } } for_each_console(c) { + if (!(c->flags & CON_ENABLED)) + continue; + bust_spinlocks(1); c->write(c, cp, retlen - (cp - kdb_buffer)); + bust_spinlocks(0); touch_nmi_watchdog(); } } @@ -761,7 +765,11 @@ int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap) } } for_each_console(c) { + if (!(c->flags & CON_ENABLED)) + continue; + bust_spinlocks(1); c->write(c, moreprompt, strlen(moreprompt)); + bust_spinlocks(0); touch_nmi_watchdog(); } -- 2.7.4