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=-11.3 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,USER_AGENT_SANE_1 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 04F91C43461 for ; Tue, 15 Sep 2020 16:26:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BC59420738 for ; Tue, 15 Sep 2020 16:26:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="b2QyoeG9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727680AbgIOQZ1 (ORCPT ); Tue, 15 Sep 2020 12:25:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:23192 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727331AbgIOPim (ORCPT ); Tue, 15 Sep 2020 11:38:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600184262; 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=EmGrGH1ln4DKY4ewYIRXTs91iln6HTRv+ClUeKFLEss=; b=b2QyoeG941G7Eg8JiZC4HkN2SXgP0/AGpS6HniXwDIxyEhmplLk9howtB/Sj5Fy6h3IkVL e8xN39LKC3r1st87lASNj3+6nYOBjOB4B5Avy7OHPtLulrNWIMgVGMdCSIeqI30VXgdgbd 46Br+UvJmnMI380Pca/OXu/f8BQfYIM= 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-381-R4v6z8tHOkSyi745y3kBZg-1; Tue, 15 Sep 2020 11:35:26 -0400 X-MC-Unique: R4v6z8tHOkSyi745y3kBZg-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 1ECD31868410; Tue, 15 Sep 2020 15:35:25 +0000 (UTC) Received: from Diego (unknown [10.40.208.57]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3DA9F75138; Tue, 15 Sep 2020 15:35:22 +0000 (UTC) Date: Tue, 15 Sep 2020 17:35:20 +0200 (CEST) From: Michael Petlan X-X-Sender: Michael@Diego To: Jiri Olsa cc: Namhyung Kim , Jiri Olsa , Peter Zijlstra , Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Alexander Shishkin , Wade Mealing Subject: Re: [PATCH] perf: Fix race in perf_mmap_close function In-Reply-To: <20200914205936.GD1714160@krava> Message-ID: References: <20200910104153.1672460-1-jolsa@kernel.org> <20200910144744.GA1663813@krava> <20200911074931.GA1714160@krava> <20200914205936.GD1714160@krava> User-Agent: Alpine 2.20 (LRH 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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, 14 Sep 2020, Jiri Olsa wrote: > 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 I've tested the change and seems OK to me. Tested-by: Michael Petlan > > > > > 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; > > > > > > /* > > > > > >