From nobody Sun May 31 17:18:46 2026 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 CFE3BC433F5 for ; Mon, 14 Feb 2022 13:45:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354598AbiBNNqF (ORCPT ); Mon, 14 Feb 2022 08:46:05 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:57994 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354618AbiBNNpo (ORCPT ); Mon, 14 Feb 2022 08:45:44 -0500 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8C5D575F4 for ; Mon, 14 Feb 2022 05:45:33 -0800 (PST) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 21ECVusW014630; Mon, 14 Feb 2022 13:45:18 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding; s=pp1; bh=t/xh7h782UBN/jZbD91JVD9rwY0PYE6Ef7A2XaPovz0=; b=LDaIM6W45eWmucJPJxrvRoAEGE7zsy9TmhAUbW33wkwMCOBMB3FHWEpm8pQwb1eCjk07 o0MzcUO0R//2AbtKQLXTsFF+uZJqmWNWH5lTHU2hPzMsZL32N+5LP4nunFXMuADFM3Zw WV5Vu7u8/oUdF9P9K9Ble3hr1xejZUA4x2gfdWIibriBss6v9WgD/y1LePQvvNNq4FRF JIv0eA8gIsjbekgx9fu4dxtciSmJFR/1SQqntiTwGZfJABdsJUMjeU3EiKriNPMxjflv TzPxlbrUc2mfGjJnyZQPzt4/6qMslnFVk1VRl3uxRjIgpeLpW/yvHboAkaFIB4BeSOPJ Bg== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3e6rt1624p-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 14 Feb 2022 13:45:18 +0000 Received: from m0098410.ppops.net (m0098410.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 21EDQQEf032307; Mon, 14 Feb 2022 13:45:17 GMT Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 3e6rt1623q-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 14 Feb 2022 13:45:17 +0000 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 21EDhnGj019890; Mon, 14 Feb 2022 13:45:15 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma03ams.nl.ibm.com with ESMTP id 3e64h9nx3a-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 14 Feb 2022 13:45:15 +0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 21EDjCb336110832 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 14 Feb 2022 13:45:13 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DA19C42045; Mon, 14 Feb 2022 13:45:12 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C8F584204F; Mon, 14 Feb 2022 13:45:12 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 14 Feb 2022 13:45:12 +0000 (GMT) Received: by tuxmaker.boeblingen.de.ibm.com (Postfix, from userid 55390) id 7F15AE02E8; Mon, 14 Feb 2022 14:45:12 +0100 (CET) From: Sven Schnelle To: Steven Rostedt , Ingo Molnar Cc: linux-kernel@vger.kernel.org, Sven Schnelle Subject: [PATCH] ftrace: ensure trace buffer is at least 4096 bytes large Date: Mon, 14 Feb 2022 14:44:56 +0100 Message-Id: <20220214134456.1751749-1-svens@linux.ibm.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: -0CZ3F6oPakx4SvErDd_hRaL7qjAqMzj X-Proofpoint-ORIG-GUID: RzYc1BmW-MYduAmjfnhD0JJV_T175gh4 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-02-14_06,2022-02-14_03,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 impostorscore=0 suspectscore=0 priorityscore=1501 phishscore=0 clxscore=1015 mlxscore=0 lowpriorityscore=0 adultscore=0 spamscore=0 bulkscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2202140082 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Booting the kernel with 'trace_buf_size=3D1' 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=3D0 ..FAILED! [ 1.353474] ------------[ cut here ]------------ [ 1.353478] WARNING: CPU: 0 PID: 1 at kernel/trace/trace.c:1951 run_trac= er_selftest+0x13c/0x1b0 Therefore enforce a minimum of 4096 bytes to make the selftest pass. Signed-off-by: Sven Schnelle --- 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 7c2578efde26..3050892d1812 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1474,10 +1474,12 @@ static int __init set_buf_size(char *str) if (!str) return 0; buf_size =3D memparse(str, &str); - /* nr_entries can not be zero */ - if (buf_size =3D=3D 0) - return 0; - trace_buf_size =3D 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 =3D max(4096UL, buf_size); return 1; } __setup("trace_buf_size=3D", set_buf_size); --=20 2.32.0