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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 14AA5C433F5 for ; Tue, 2 Nov 2021 11:43:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC7AC60295 for ; Tue, 2 Nov 2021 11:43:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230208AbhKBLpp (ORCPT ); Tue, 2 Nov 2021 07:45:45 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:25343 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230102AbhKBLpo (ORCPT ); Tue, 2 Nov 2021 07:45:44 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Hk7FR6KNyzbhXr; Tue, 2 Nov 2021 19:38:19 +0800 (CST) Received: from dggpeml500024.china.huawei.com (7.185.36.10) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Tue, 2 Nov 2021 19:43:01 +0800 Received: from [10.174.176.231] (10.174.176.231) by dggpeml500024.china.huawei.com (7.185.36.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Tue, 2 Nov 2021 19:43:01 +0800 To: , , , , Andrew Morton , , , CC: , , , , , Hewenliang From: Yunfeng Ye Subject: [PATCH v2] mm, slub: emit the "free" trace report before freeing memory in kmem_cache_free() Message-ID: Date: Tue, 2 Nov 2021 19:43:00 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.176.231] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500024.china.huawei.com (7.185.36.10) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After the memory is freed, it can be immediately allocated by other CPUs, before the "free" trace report has been emitted. This causes inaccurate traces. For example, if the following sequence of events occurs: CPU 0 CPU 1 (1) alloc xxxxxx (2) free xxxxxx (3) alloc xxxxxx (4) free xxxxxx Then they will be inaccurately reported via tracing, so that they appear to have happened in this order: CPU 0 CPU 1 (1) alloc xxxxxx (2) alloc xxxxxx (3) free xxxxxx (4) free xxxxxx This makes it look like CPU 1 somehow managed to allocate mmemory that CPU 0 still had allocated for itself. In order to avoid this, emit the "free xxxxxx" tracing report just before the actual call to free the memory, instead of just after it. Signed-off-by: Yunfeng Ye Reviewed-by: Vlastimil Babka --- v1 -> v2: - Modify the description - Add "Reviewed-by" mm/slub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/slub.c b/mm/slub.c index 432145d7b4ec..427e62034c3f 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3526,8 +3526,8 @@ void kmem_cache_free(struct kmem_cache *s, void *x) s = cache_from_obj(s, x); if (!s) return; - slab_free(s, virt_to_head_page(x), x, NULL, 1, _RET_IP_); trace_kmem_cache_free(_RET_IP_, x, s->name); + slab_free(s, virt_to_head_page(x), x, NULL, 1, _RET_IP_); } EXPORT_SYMBOL(kmem_cache_free); -- 2.27.0