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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1DB53C433F5 for ; Tue, 1 Mar 2022 20:25:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238365AbiCAU0S (ORCPT ); Tue, 1 Mar 2022 15:26:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238827AbiCAUXz (ORCPT ); Tue, 1 Mar 2022 15:23:55 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1A2241607; Tue, 1 Mar 2022 12:21:21 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 665B760AE2; Tue, 1 Mar 2022 20:21:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4A65C340EE; Tue, 1 Mar 2022 20:21:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646166079; bh=HyUK9pZg1FGxaTxvcSjI4+U0M90v9UG/SsfsqFETqCY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fnlBQEDm+IH25qqwrufIrklI3irwOtxlNw+ePItMI38yWewISaBNOHhQYNHzy7dnH BCpHBWpY5HbfUVlSXXWWlL3lJdpCIu0s9YMmD4DdnAjgxn6XkeUXY0bVZcZ4fPe1er smGfJwaBbctdWL1Bi/6FsgDquYXxeK8B511xl61h66TjOZwabCo5DGRK9nlmLQPdoN /S2WiM9QRUjyHYzELTvZ7SgqmgQ3wS3Q9+5atefry6h09aFeEreVtc8aiWlF7CPHVM xNcn1S6HOTiGNb9rKvpwLyRLq3xDSIIb5wHyXyyYxyST3OXS8a29QhF5oUGLT0ij5p E/HGYXUcJPHTA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sven Schnelle , Steven Rostedt , Sasha Levin , mingo@redhat.com Subject: [PATCH AUTOSEL 4.19 6/7] tracing: Ensure trace buffer is at least 4096 bytes large Date: Tue, 1 Mar 2022 15:20:44 -0500 Message-Id: <20220301202046.19220-6-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220301202046.19220-1-sashal@kernel.org> References: <20220301202046.19220-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sven Schnelle [ Upstream commit 7acf3a127bb7c65ff39099afd78960e77b2ca5de ] Booting the kernel with 'trace_buf_size=1' give a warning at boot during the ftrace selftests: [ 0.892809] Running postponed tracer tests: [ 0.892893] Testing tracer function: [ 0.901899] Callback from call_rcu_tasks_trace() invoked. [ 0.983829] Callback from call_rcu_tasks_rude() invoked. [ 1.072003] .. bad ring buffer .. corrupted trace buffer .. [ 1.091944] Callback from call_rcu_tasks() invoked. [ 1.097695] PASSED [ 1.097701] Testing dynamic ftrace: .. filter failed count=0 ..FAILED! [ 1.353474] ------------[ cut here ]------------ [ 1.353478] WARNING: CPU: 0 PID: 1 at kernel/trace/trace.c:1951 run_tracer_selftest+0x13c/0x1b0 Therefore enforce a minimum of 4096 bytes to make the selftest pass. Link: https://lkml.kernel.org/r/20220214134456.1751749-1-svens@linux.ibm.com Signed-off-by: Sven Schnelle Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin --- kernel/trace/trace.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 19a6b088f1e72..063b434c89d26 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1118,10 +1118,12 @@ static int __init set_buf_size(char *str) if (!str) return 0; buf_size = memparse(str, &str); - /* nr_entries can not be zero */ - if (buf_size == 0) - return 0; - trace_buf_size = buf_size; + /* + * nr_entries can not be zero and the startup + * tests require some buffer space. Therefore + * ensure we have at least 4096 bytes of buffer. + */ + trace_buf_size = max(4096UL, buf_size); return 1; } __setup("trace_buf_size=", set_buf_size); -- 2.34.1