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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 00044C48BD5 for ; Tue, 25 Jun 2019 12:20:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C2CAA213F2 for ; Tue, 25 Jun 2019 12:20:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729997AbfFYMUh (ORCPT ); Tue, 25 Jun 2019 08:20:37 -0400 Received: from mga03.intel.com ([134.134.136.65]:62516 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726930AbfFYMUh (ORCPT ); Tue, 25 Jun 2019 08:20:37 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Jun 2019 05:20:36 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,415,1557212400"; d="scan'208";a="155494457" Received: from um.fi.intel.com (HELO localhost) ([10.237.72.63]) by orsmga008.jf.intel.com with ESMTP; 25 Jun 2019 05:20:33 -0700 From: Alexander Shishkin To: Peter Zijlstra , Mark Rutland Cc: Arnaldo Carvalho de Melo , Ingo Molnar , linux-kernel@vger.kernel.org, jolsa@redhat.com, dvyukov@google.com, namhyung@kernel.org, xiexiuqi@huawei.com, syzbot+a24c397a29ad22d86c98@syzkaller.appspotmail.com, alexander.shishkin@linux.intel.com Subject: Re: [PATCH] perf: Fix race between close() and fork() In-Reply-To: <20190625104320.GZ3463@hirez.programming.kicks-ass.net> References: <278ac311-d8f3-2832-5fa1-522471c8c31c@huawei.com> <20190228140109.64238-1-alexander.shishkin@linux.intel.com> <20190308155429.GB10860@lakrids.cambridge.arm.com> <20190624121902.GE3436@hirez.programming.kicks-ass.net> <20190625084904.GY3463@hirez.programming.kicks-ass.net> <20190625104320.GZ3463@hirez.programming.kicks-ass.net> Date: Tue, 25 Jun 2019 15:20:33 +0300 Message-ID: <87h88dvotq.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > Solve it by using the fact that detached events still have a reference > count on their (previous) context. With this perf_event_free_task() > can detect when events have escaped and wait for their destruction. > > Cc: Mark Rutland > Fixes: 82d94856fa22 ("perf/core: Fix lock inversion between perf,trace,cpuhp") > Reported-by: syzbot+a24c397a29ad22d86c98@syzkaller.appspotmail.com > Debugged-by: Alexander Shishkin > Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Alexander Shishkin Regards, -- Alex