From nobody Fri Sep 20 20:29:32 2024 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 44AD3C7619A for ; Sun, 9 Apr 2023 02:47:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229533AbjDICqk (ORCPT ); Sat, 8 Apr 2023 22:46:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229446AbjDICqj (ORCPT ); Sat, 8 Apr 2023 22:46:39 -0400 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23D4C5B95; Sat, 8 Apr 2023 19:46:32 -0700 (PDT) X-UUID: b8d2775cd68011eda9a90f0bb45854f4-20230409 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:CC:To:From; bh=RT6t6k0uRnv8KRrBTo9piwxXohY+DCmlYMyknmWtfNY=; b=XlJT9ba5DtASdgzl0yqtzF/plWLN4TQikNU5tYUbcABPolQ5egdmArdBqwZIHvlK2EsoWekcjsTTC0adODFBSrPwRi+5abfhQmB54+hu39rNJWR7seMOmcSXtI8kbAmOtUxpxKbT6NGpsmeTUynfycl0Sr67qftoDmnsQIkgxmU=; X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.22,REQID:0072c493-e98d-4941-995d-dd8cc0cc4503,IP:0,U RL:0,TC:0,Content:-25,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTIO N:release,TS:-25 X-CID-META: VersionHash:120426c,CLOUDID:5ac19eb5-beed-4dfc-bd9c-e1b22fa6ccc4,B ulkID:nil,BulkQuantity:0,Recheck:0,SF:102,TC:nil,Content:0,EDM:-3,IP:nil,U RL:1,File:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0 X-CID-BVR: 0 X-CID-BAS: 0,_,0,_ X-UUID: b8d2775cd68011eda9a90f0bb45854f4-20230409 Received: from mtkmbs13n2.mediatek.inc [(172.21.101.108)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 1597067467; Sun, 09 Apr 2023 10:46:26 +0800 Received: from mtkmbs11n1.mediatek.inc (172.21.101.185) by mtkmbs10n2.mediatek.inc (172.21.101.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.25; Sun, 9 Apr 2023 10:46:24 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkmbs11n1.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.1118.25 via Frontend Transport; Sun, 9 Apr 2023 10:46:24 +0800 From: Tze-nan Wu To: , CC: , , , , "AngeloGioacchino Del Regno" , , , , Subject: [PATCH v2] ring-buffer: Prevent inconsistent operation on cpu_buffer->resize_disabled Date: Sun, 9 Apr 2023 10:46:15 +0800 Message-ID: <20230409024616.31099-1-Tze-nan.Wu@mediatek.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20230408052226.25268-1-Tze-nan.Wu@mediatek.com> References: <20230408052226.25268-1-Tze-nan.Wu@mediatek.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Write to buffer_size_kb can permanently fail due to cpu_online_mask changed between two for_each_online_buffer_cpu loops. The number of increasing and decreasing on cpu_buffer->resize_disable may be inconsistent, leading that the resize_disabled in some CPUs becoming none zero after ring_buffer_reset_online_cpus return. This issue can be reproduced by "echo 0 > trace" and hotplug cpu at the same time. After reproducing success, we can find out buffer_size_kb will not be functional anymore. This patch uses cpus_read_lock() to prevent cpu_online_mask being changed between two different "for_each_online_buffer_cpu". Changes in v2: Use cpus_read_lock() instead of copying cpu_online_mask at the entry of function Link: https://lore.kernel.org/lkml/20230408052226.25268-1-Tze-nan.Wu@mediatek.c= om/ Cc: stable@vger.kernel.org Signed-off-by: Tze-nan Wu --- kernel/trace/ring_buffer.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 76a2d91eecad..44d833252fb0 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -5357,6 +5357,7 @@ void ring_buffer_reset_online_cpus(struct trace_buffe= r *buffer) =20 /* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex); + cpus_read_lock(); =20 for_each_online_buffer_cpu(buffer, cpu) { cpu_buffer =3D buffer->buffers[cpu]; @@ -5377,6 +5378,7 @@ void ring_buffer_reset_online_cpus(struct trace_buffe= r *buffer) atomic_dec(&cpu_buffer->resize_disabled); } =20 + cpus_read_unlock(); mutex_unlock(&buffer->mutex); } =20 --=20 2.18.0