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=-9.8 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 78394C433DF for ; Wed, 27 May 2020 06:26:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5074120787 for ; Wed, 27 May 2020 06:26:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="G85xHZqL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728533AbgE0G0v (ORCPT ); Wed, 27 May 2020 02:26:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728003AbgE0G0u (ORCPT ); Wed, 27 May 2020 02:26:50 -0400 Received: from mail-pj1-x1042.google.com (mail-pj1-x1042.google.com [IPv6:2607:f8b0:4864:20::1042]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 93F2CC061A0F for ; Tue, 26 May 2020 23:26:50 -0700 (PDT) Received: by mail-pj1-x1042.google.com with SMTP id nu7so1115157pjb.0 for ; Tue, 26 May 2020 23:26:50 -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:in-reply-to:references; bh=tSNP35QYp6xethZiWpN7Amg3X+LW4hgKA/e4KGUMccc=; b=G85xHZqLsrWZHmuuol1ub48HKxIZv5mdMUnm3b8yhDQMn6qJH4go9eNLKJHEduMHCw 5oWiGqTR6R3Lvvs162rEhlcPapcPlp9s1LdpwgUxegA0hZkPCEEbHUlFw2/3jL0Cal8c Ald7vkGE8pEFiTwJftEVdcJnU4Bos8caP5Pi18190rIeTGVdbLLnGPZUA3+MpI6z86xe Axtl7GI6AkUDP+XLxRcgRSMd5a4tL7OlEiOnSwRh0YujnzdzkRNCN47W+u75SD8ENOcY 4VahJAFqcN3JceEn3SOat3kt7OqkIjCpofGgPZ+LlmUX2Fp+nhYGTkuIqsGUvUMoeVco y81w== 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:in-reply-to :references; bh=tSNP35QYp6xethZiWpN7Amg3X+LW4hgKA/e4KGUMccc=; b=C/zc4N8+7sC3LDndOV1Tr9CJRQjCWv3B5FvdQIOni30vhPBXPXPp4LWfHEFOtxb+Sm egejEyQyI9DV8wOKTNyiDtwvRZHo+1mQMHum+rtkhr7bN4edp0eMK8enCLhSWsQnHAeR P5x7QWOCW6MfxhMNDSuOH145oi43YnWeC3C0ES4szla0+DImjmh0T7IYkrOPX9/RLnZj PAy1tYXbBTAqXgpKpwG8w3HXC03flHzsrAlBu/xsGDS0UEuiWT2V5Q6aRrK1wKLyY2mW 3Ro0NQhEzt87piD0xyF2ujzVIeNbS2KhzH09EmtDr3tvELMIivmBI74cKNmcJIx8fYwv BJUQ== X-Gm-Message-State: AOAM532xbtZJxQVOVfBJ/1m3+2kkRqMNyplHwb8bH5O+idA8scGb6/P9 TgKaosdyayWfOXRkKjuDLB5Xig== X-Google-Smtp-Source: ABdhPJzEHo4EV0Nw7baAgnSJBBSDsFWrG9xwKApSsxlEfzYi9UM/tqokhAtut1Lf1zGSTCSpFgSJjA== X-Received: by 2002:a17:902:b904:: with SMTP id bf4mr4500929plb.89.1590560810119; Tue, 26 May 2020 23:26:50 -0700 (PDT) Received: from localhost.localdomain ([117.252.68.136]) by smtp.gmail.com with ESMTPSA id m12sm1239121pjs.41.2020.05.26.23.26.45 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 May 2020 23:26:49 -0700 (PDT) From: Sumit Garg To: daniel.thompson@linaro.org Cc: kgdb-bugreport@lists.sourceforge.net, jason.wessel@windriver.com, dianders@chromium.org, pmladek@suse.com, sergey.senozhatsky@gmail.com, linux-kernel@vger.kernel.org, Sumit Garg Subject: [PATCH v3 3/4] kdb: Make kdb_printf robust to run in NMI context Date: Wed, 27 May 2020 11:55:58 +0530 Message-Id: <1590560759-21453-4-git-send-email-sumit.garg@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1590560759-21453-1-git-send-email-sumit.garg@linaro.org> References: <1590560759-21453-1-git-send-email-sumit.garg@linaro.org> 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, enable oops_in_progress prior to invocation of console handlers. Suggested-by: Petr Mladek Signed-off-by: Sumit Garg --- kernel/debug/kdb/kdb_io.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 349dfcc..f848482 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -566,7 +566,17 @@ static void kdb_msg_write(char *msg, int msg_len) for_each_console(c) { if (!(c->flags & CON_ENABLED)) continue; + /* + * 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, enable oops_in_progress + * prior to invocation of console handlers. + */ + ++oops_in_progress; c->write(c, msg, msg_len); + --oops_in_progress; touch_nmi_watchdog(); } } -- 2.7.4