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 X-Spam-Level: X-Spam-Status: No, score=-8.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A1C0EC2BC11 for ; Mon, 14 Sep 2020 12:53:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 670B4206B2 for ; Mon, 14 Sep 2020 12:53:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600088030; bh=GBOeRLJMpN8lOepNH6p+W244BoMvEnxIk+jH4mDq7mA=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=Mu6qLjHO59ECvsOu6STWIofmSrK73BbyfSd6twB73JyUGVTh0ErEbJr4YL4rouVsr 5altxd8SW/2DxZucff/kb8A5mx9kwQC4mVLlSw9OBwprtFBG3iERs1EeH5NJ5zf4d0 BIqi6lkwPHgnypCUvlBTykEMhKg+uuO4YQhi6HuM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726604AbgINMxq (ORCPT ); Mon, 14 Sep 2020 08:53:46 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:44625 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726522AbgINMs4 (ORCPT ); Mon, 14 Sep 2020 08:48:56 -0400 Received: by mail-wr1-f67.google.com with SMTP id s12so18560946wrw.11 for ; Mon, 14 Sep 2020 05:48:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Vlodagcs22zibyjAPJ5wkLwD6Gf2F5qWiI3JD8jZYsQ=; b=qC9C3N9+rdw3iLl5qzvmdCJLQAeQmadtzo2LnMjp0X8v0Ju3JB5e7M7FBWBwbZr3T9 ib2bifDPu4TbMLXvB1M6eTzXmtSYyfWDX4wgiMWe7wUzCwKtx0WHkJfNK3Ak2pFXmaOA bV2JGuG1mtPMjJ2F5pWl/unZSbRDe6hylIrQQqsoVqgUt86zU+y7gaUnREvBpxpYPza7 vCmscwVmLId9KHxZOt0rk3x1XVMt60SQ5N7AkJwi4QAxydEd83AnMCsFYA9zskq8MFcb I+UbykEghMyGTGOVfAMaDM/kWVKcijnA2d1YGTJXUBtbVdkHn5+wez7cyONqfwVogY1f UIgw== X-Gm-Message-State: AOAM532vWHpqH64BEhAzB1D0+U59BovbMakc6iHLUxcB3lvLlPk+lnAP Fbpy9/grnb/kOsZHqPdBUfiwHf1fv6bHlxSZ+cM= X-Google-Smtp-Source: ABdhPJzfXebMcTIcP3VuxaK0KNmDajg+JlhKL+03BerqsLLLWO0vfjbdTd003Mh+CktpWyDIqOmbs6kNHO22IU02vYY= X-Received: by 2002:adf:a418:: with SMTP id d24mr7943993wra.80.1600087734486; Mon, 14 Sep 2020 05:48:54 -0700 (PDT) MIME-Version: 1.0 References: <20200910104153.1672460-1-jolsa@kernel.org> <20200910144744.GA1663813@krava> <20200911074931.GA1714160@krava> In-Reply-To: <20200911074931.GA1714160@krava> From: Namhyung Kim Date: Mon, 14 Sep 2020 21:48:43 +0900 Message-ID: Subject: Re: [PATCH] perf: Fix race in perf_mmap_close function To: Jiri Olsa Cc: Jiri Olsa , Peter Zijlstra , Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Alexander Shishkin , Michael Petlan , Wade Mealing Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 11, 2020 at 4:49 PM Jiri Olsa wrote: > ugh, that's right.. how about change below Acked-by: Namhyung Kim Thanks Namhyung > > jirka > > > --- > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 7ed5248f0445..8ab2400aef55 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -5868,11 +5868,11 @@ static void perf_pmu_output_stop(struct perf_event *event); > static void perf_mmap_close(struct vm_area_struct *vma) > { > struct perf_event *event = vma->vm_file->private_data; > - > struct perf_buffer *rb = ring_buffer_get(event); > struct user_struct *mmap_user = rb->mmap_user; > int mmap_locked = rb->mmap_locked; > unsigned long size = perf_data_size(rb); > + bool detach_rest = false; > > if (event->pmu->event_unmapped) > event->pmu->event_unmapped(event, vma->vm_mm); > @@ -5903,7 +5903,8 @@ static void perf_mmap_close(struct vm_area_struct *vma) > mutex_unlock(&event->mmap_mutex); > } > > - atomic_dec(&rb->mmap_count); > + if (atomic_dec_and_test(&rb->mmap_count)) > + detach_rest = true; > > if (!atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) > goto out_put; > @@ -5912,7 +5913,7 @@ static void perf_mmap_close(struct vm_area_struct *vma) > mutex_unlock(&event->mmap_mutex); > > /* If there's still other mmap()s of this buffer, we're done. */ > - if (atomic_read(&rb->mmap_count)) > + if (!detach_rest) > goto out_put; > > /* >