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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 E5F79C43461 for ; Mon, 14 Sep 2020 20:59:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 843962193E for ; Mon, 14 Sep 2020 20:59:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Qd4zgB8Y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726091AbgINU7t (ORCPT ); Mon, 14 Sep 2020 16:59:49 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:57076 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725994AbgINU7s (ORCPT ); Mon, 14 Sep 2020 16:59:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600117186; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=/RZxO9Godwl44d6wJihHpSIBg4OppaEy3+dFcmyNT/E=; b=Qd4zgB8Yg4yGq0toow6aSebnhqEnEIyu/h9P1JjmgVW5SyXHEWrXSD+rhnoe0VChUXPilP xIw11DGMKnl5GlMgva8dc9kaoI7xOcZ3u63QL6/57cbB2yh096UrBvTIoRAruDgd8uXuCg Tyxsmj9ZnZZ6XQmtVjFGEuFAhqvvjtU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-20-g4njyc2UMpqR8fw3gIrB6w-1; Mon, 14 Sep 2020 16:59:45 -0400 X-MC-Unique: g4njyc2UMpqR8fw3gIrB6w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 99714800479; Mon, 14 Sep 2020 20:59:43 +0000 (UTC) Received: from krava (unknown [10.40.192.180]) by smtp.corp.redhat.com (Postfix) with SMTP id 91A8A75142; Mon, 14 Sep 2020 20:59:37 +0000 (UTC) Date: Mon, 14 Sep 2020 22:59:36 +0200 From: Jiri Olsa To: Namhyung Kim Cc: Jiri Olsa , Peter Zijlstra , Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Alexander Shishkin , Michael Petlan , Wade Mealing Subject: Re: [PATCH] perf: Fix race in perf_mmap_close function Message-ID: <20200914205936.GD1714160@krava> References: <20200910104153.1672460-1-jolsa@kernel.org> <20200910144744.GA1663813@krava> <20200911074931.GA1714160@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 14, 2020 at 09:48:43PM +0900, Namhyung Kim wrote: > 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, I'll send full patch after we're done testing this jirka > > 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; > > > > /* > > >