From patchwork Mon Mar 14 11:34:13 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 551421 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 1AB63C433EF for ; Mon, 14 Mar 2022 11:35:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239054AbiCNLgF (ORCPT ); Mon, 14 Mar 2022 07:36:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239070AbiCNLgE (ORCPT ); Mon, 14 Mar 2022 07:36:04 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8F6E041F89; Mon, 14 Mar 2022 04:34:54 -0700 (PDT) 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 3160061073; Mon, 14 Mar 2022 11:34:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A3DEC340E9; Mon, 14 Mar 2022 11:34:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1647257693; bh=+PzydsWgRvTQyto62/lDWNeq3+GlRRXHAruNmIsF+50=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QnKUX6q7rM8+0Ld6EmeNZqLskHcHDA/minyLAJU5HxySFxW+l0EtmScNLNWxM37wj EEzWo/szajpuAcxcduKTMS6+Xjt9l9Vd7NBoyAteyPpCZHUJ0S4Aq4BQek3LP/uaKv ZlEIkb30LDSASZn1ED8Md6Vow3H2hMNtOOdRZvhU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sven Schnelle , "Steven Rostedt (Google)" , Sasha Levin Subject: [PATCH 4.9 12/20] tracing: Ensure trace buffer is at least 4096 bytes large Date: Mon, 14 Mar 2022 12:34:13 +0100 Message-Id: <20220314112730.862533003@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220314112730.388955049@linuxfoundation.org> References: <20220314112730.388955049@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 12bee7043be6..90e0fd5621da 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);