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=-12.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, UNWANTED_LANGUAGE_BODY,URIBL_BLOCKED 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 9FA41C433E0 for ; Thu, 25 Feb 2021 20:25:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C03864F2A for ; Thu, 25 Feb 2021 20:25:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233578AbhBYUZ2 (ORCPT ); Thu, 25 Feb 2021 15:25:28 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:38148 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229993AbhBYUZW (ORCPT ); Thu, 25 Feb 2021 15:25:22 -0500 From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1614284680; 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: in-reply-to:in-reply-to:references:references; bh=FvEugpmlewV9gebD1OmyfIYiNAiGiwjtgRLamPmBKRk=; b=rbvwFdFLGTQWpwqv3SpQcfJSrcNDWVIEeMjAoPk7uEWMiCvlAscCCO96sM/tPm9vpTBtN+ oOeXz/znuzp7Cn+BN/ziace690e9SfEwZ33Y6LZxXn0SFyNoNf1DptRuJ71a31J257+5I5 1QaV95+dluYFn6Fekcfy4tGfUVpvcj/niKYmMGLXom3irekHBLQj3Bm7Ft7FRQNrBv83kW iBajhDO8IvYUP9o55opRHJPcs051ZdXsCTOnfoR5H8A3SZxy9xi+d+8aUzVhYyX3P73spK CVVCyYH/FJWKHF9pRHRSsG5TF9Joq06NgGnUZsNRELc22s9ot/HdNFpHwHwfjw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1614284680; 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: in-reply-to:in-reply-to:references:references; bh=FvEugpmlewV9gebD1OmyfIYiNAiGiwjtgRLamPmBKRk=; b=tnyXn4ktKUVli67LkOUpVYzz6LC1Ugo4+7U7Pj2RsxmMKeFfEHdPiAnqVsTVCJwXfuRNWK +1NA+Og0m9aYDvDg== To: Petr Mladek Cc: Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Jeff Dike , Richard Weinberger , Anton Ivanov , Thomas Meyer , Andy Shevchenko , linux-um@lists.infradead.org Subject: [PATCH next v3 01/15] um: synchronize kmsg_dumper Date: Thu, 25 Feb 2021 21:24:24 +0100 Message-Id: <20210225202438.28985-2-john.ogness@linutronix.de> In-Reply-To: <20210225202438.28985-1-john.ogness@linutronix.de> References: <20210225202438.28985-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The kmsg_dumper can be called from any context and CPU, possibly from multiple CPUs simultaneously. Since a static buffer is used to retrieve the kernel logs, this buffer must be protected against simultaneous dumping. Skip dumping if another context is already dumping. Signed-off-by: John Ogness Reviewed-by: Petr Mladek --- arch/um/kernel/kmsg_dump.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c index 6516ef1f8274..4869e2cc787c 100644 --- a/arch/um/kernel/kmsg_dump.c +++ b/arch/um/kernel/kmsg_dump.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include +#include #include #include #include @@ -9,6 +10,7 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason) { + static DEFINE_SPINLOCK(lock); static char line[1024]; struct console *con; size_t len = 0; @@ -29,11 +31,16 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, if (con) return; + if (!spin_trylock(&lock)) + return; + printf("kmsg_dump:\n"); while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) { line[len] = '\0'; printf("%s", line); } + + spin_unlock(&lock); } static struct kmsg_dumper kmsg_dumper = { -- 2.20.1