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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 C6094ECDE5F for ; Tue, 24 Jul 2018 01:44:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6D1D520852 for ; Tue, 24 Jul 2018 01:44:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="SWW0Zp6U" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6D1D520852 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388332AbeGXCsx (ORCPT ); Mon, 23 Jul 2018 22:48:53 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:36324 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388267AbeGXCsw (ORCPT ); Mon, 23 Jul 2018 22:48:52 -0400 Received: by mail-pf1-f193.google.com with SMTP id d14-v6so456497pfo.3 for ; Mon, 23 Jul 2018 18:44:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=XdVS798Ju2Hyug1eNSX0YMXJcbEBDzmh9IAjzKqwFFQ=; b=SWW0Zp6UE5togTYcZFwlnrFh8jrABELquR4ZL6BN+YiwDixgZ+uacEFajQ7F3EMUvH ikB75B9hLyV2dEC9vHJ5PEs128oUNQ24WKCEGnNJTkhTnURkKcpeCESDvXpKKP68bjAB RijhSGUpAosNn2ltOpdsWLbjvFNN0ZshM8U0BsdD/V00jDrantyTWaNX8EpnpaCugbp6 YD8I1cTZRnS8kLwPUmpJ+SoNwHtGNZWgNsDxgW3pqoElrxJWsDpQSaIGmleLvXq/Dw+S 8qHQ43qpqFNZw4u0QITT3w5j6l0l6Hn6dpMEezFmjTiQqkQozG6OjH+1jGIuMUmAXVND 6oxA== 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=XdVS798Ju2Hyug1eNSX0YMXJcbEBDzmh9IAjzKqwFFQ=; b=b+rrR6auEYMGpotlZ0Cw+CCdvGeSmhTPZPj2BvzKa7e2V9GfStXJiQNosZx/8EMdP3 R9EI5EKtxqCv2iZbrZneJsloiixDmmQIyuK7KQm56uD3/MHFpA1N9q+7eIMmdOyuun/E YCtjLD4I7zjCAHFZJGjwghCjf2O3I/4bnOIfEb/BJ3AnxfGJrgiKpZSENb0bimWNx1wq PeptYRRhFBtaKzOt4a9kyRmjGbFf9/8oDdDy71Jjp+tLPngytbWiLppSOAOEVgwLynv0 kAs2nwVa8RKTHwmu4DCBsudZ5ekzpaeBbseej2hj/tO2l2cjSaiHGLU0ctmplrxjPcgQ BO6w== X-Gm-Message-State: AOUpUlE9opCSZvjBGamfFdKjzc9MB1OowOTE/eaxnqiuYs+LGATPXUlK kBG1Gtq99FWJ96pGuW5nxiePWC/UK9Lg1Yx2F44FssLe X-Google-Smtp-Source: AAOMgpeA80nEwV9q46vtg5VbP16JRIUjGUI5pdU3o1ZY8Fu04R903VyuGVDQP3s+QDSopO/U29QaEKw11der3+5oi4s= X-Received: by 2002:a62:cd3:: with SMTP id 80-v6mr15750439pfm.184.1532396695052; Mon, 23 Jul 2018 18:44:55 -0700 (PDT) MIME-Version: 1.0 References: <20180719132834.GF18667@krava> <20180719191253.3843-1-xiyou.wangcong@gmail.com> <20180720115217.GQ2494@hirez.programming.kicks-ass.net> In-Reply-To: From: Cong Wang Date: Mon, 23 Jul 2018 18:44:43 -0700 Message-ID: Subject: Re: [PATCH v2] perf/core: fix a possible deadlock scenario To: Peter Zijlstra Cc: LKML , Ingo Molnar , Linus Torvalds , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Andi Kleen 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 Mon, Jul 23, 2018 at 6:35 PM Cong Wang wrote: > > Hi, Peter, Andi > > While reviewing the deadlock, I find out it looks like we could have the > following infinite recursion too: > > perf_event_account_interrupt() > __perf_event_account_interrupt() > perf_adjust_period() > event->pmu->stop > x86_pmu_stop() > x86_pmu.disable() Hmm, x86_pmu_stop() calls __test_and_clear_bit(), so we should not call x86_pmu.disable() twice here. > intel_pmu_disable_event() > intel_pmu_pebs_disable() > intel_pmu_drain_pebs_buffer() > intel_pmu_drain_pebs_nhm() > > > This time is pure hardware events, attr.freq must be non-zero. > > And, we could enter this infinite recursion in NMI handler too: > > intel_pmu_handle_irq() > perf_event_overflow() > __perf_event_overflow() > __perf_event_account_interrupt() > .... > > Or this is impossible too? > > Thanks!