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 BAC3DC4321E for ; Tue, 1 Mar 2022 20:27:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238587AbiCAU2R (ORCPT ); Tue, 1 Mar 2022 15:28:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239256AbiCAUYh (ORCPT ); Tue, 1 Mar 2022 15:24:37 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 222344249C; Tue, 1 Mar 2022 12:22:42 -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 ams.source.kernel.org (Postfix) with ESMTPS id CFC9FB81D4E; Tue, 1 Mar 2022 20:22:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4FE04C340EE; Tue, 1 Mar 2022 20:22:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646166159; bh=BDnBhaYylqMWjGosUmpheFv+jQ3QbOsW+wySpY/V6y0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XzYtY5Gh6ZeDqaKALEB5zcd8MGDxP32CuXLR8sPN5J1XFfh20Pm4+7pmvf+54Lqeq 5MSF3yjtF1p2dK0DhWNt19SgNjSX7aSyB9b3EUwBY54jzQ83g2vKIYDRxB8znyVEc+ V9XH2BR613o3lSy4A9IBi/yqi49tFlnhT5AyfjeiaFmusxXGcdf+4IOhZ52i40A8TV K1dANVk6mdLdm5I2DDHu9Qsc6cxWZ2RO9XB5ksAl/+TZYiheVh4nSN41QIz+PT5Xd4 9A44WUulMzErQ7hz0LeYSryc6ziigbAFjafUfRBw9b78azfKhBdDu6bp4GbTm/huR0 pV94LINrvFjaA== 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 4.9 5/6] tracing: Ensure trace buffer is at least 4096 bytes large Date: Tue, 1 Mar 2022 15:22:09 -0500 Message-Id: <20220301202212.19419-5-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220301202212.19419-1-sashal@kernel.org> References: <20220301202212.19419-1-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 12bee7043be6f..90e0fd5621da9 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1077,10 +1077,12 @@ 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