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,URIBL_BLOCKED,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 BEDE3C433E0 for ; Fri, 22 May 2020 14:34:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 846402333C for ; Fri, 22 May 2020 14:34:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="IA4Vzz42" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730003AbgEVOeQ (ORCPT ); Fri, 22 May 2020 10:34:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54500 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729851AbgEVOeQ (ORCPT ); Fri, 22 May 2020 10:34:16 -0400 Received: from mail-pl1-x644.google.com (mail-pl1-x644.google.com [IPv6:2607:f8b0:4864:20::644]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DED9EC061A0E for ; Fri, 22 May 2020 07:34:15 -0700 (PDT) Received: by mail-pl1-x644.google.com with SMTP id x18so3355534pll.6 for ; Fri, 22 May 2020 07:34:15 -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=jt95gM7bDaZUZl096LfhQlytpSjYv3RkW970ThzaFFA=; b=IA4Vzz42923hj72QNNcuVRP/Txsfsry0y7VVQ453xTFlJkzgmIqq5tWR1wl7ywD7jE ff9YJ72Pa1DMNZfT/neHIll7EA8oHhxHsYA811SYOTMpoVoaVlqCpQAuMzIuMh5pSWjS Webi0gLSSquYMpAoUA139QPmQDlz6IT/fR2bLQ9udlwxdRp2pyvi4VAI+ivSmXEkfF7a 0TK+s81lg1eOw1GX5Txyhs11DZkjcC64QtTbqq7KgQUKCoZR3idaEbR+Awh1wrzagGE1 OzOh/mM0H6DqIjcmX6zmrWyGiLpZldAxi/u8hm/NO439ICLl+RJyLDjfVVPovBaKLb13 vzYw== 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=jt95gM7bDaZUZl096LfhQlytpSjYv3RkW970ThzaFFA=; b=CyvoT2wFNIfigiu421pVb6713E3HxCs23h1zw7ISwJ5nQA3VlUmj+qGNBoRo+KDcVF vohNpLcnCmRJWLDBdR1yFr/p4XI8C7RJ6f54YP/NjGMata8jjc71HHk/s3vJqAUcoslO LY15G7kxRvW1s+AivYcOstvAC67tY1F5OZEINQQm0tFSN9S0Au7ThVUy499CWZ/9y3aB dx9Zc/Tp4BiPE5dShyYVRxl+z9qSm1TwAetmxUgx3ejJD71VFNIUAOdko9KP1T6tn+iH 6aIlVruUAUsxyeiQen9edgEDmlv9a+6Bb80h0G2+VyDAMVD+2jkq3CImOKB1fxpCpTgP ZMbw== X-Gm-Message-State: AOAM5325fhN/1Sz5CY3pg+Ta+77ybMxDhWBbagXdAelxsYVzuodZw/75 o24P/9iwX9Es+x+GkSIL0LGyLQ== X-Google-Smtp-Source: ABdhPJwL0Aom7OL3QO7sP6rWI4bhVxcyO1dbOlAn6mkTgxiIBT3D8I7zFT6+ruJ9GGI9iCbEmyr17A== X-Received: by 2002:a17:90a:f0d8:: with SMTP id fa24mr4722575pjb.93.1590158055272; Fri, 22 May 2020 07:34:15 -0700 (PDT) Received: from localhost.localdomain ([117.252.68.136]) by smtp.gmail.com with ESMTPSA id r2sm7247889pfq.194.2020.05.22.07.34.10 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 May 2020 07:34:14 -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 v2] kdb: Make kdb_printf robust to run in NMI context Date: Fri, 22 May 2020 20:03:47 +0530 Message-Id: <1590158027-15254-1-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 --- Changes in v2: - Use oops_in_progress directly instead of bust_spinlocks(). 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..3a5a068 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; + ++oops_in_progress; c->write(c, cp, retlen - (cp - kdb_buffer)); + --oops_in_progress; 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; + ++oops_in_progress; c->write(c, moreprompt, strlen(moreprompt)); + --oops_in_progress; touch_nmi_watchdog(); } -- 2.7.4