From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754208Ab0KIREh (ORCPT ); Tue, 9 Nov 2010 12:04:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:6326 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751972Ab0KIREe (ORCPT ); Tue, 9 Nov 2010 12:04:34 -0500 Date: Tue, 9 Nov 2010 17:58:05 +0100 From: Oleg Nesterov To: Peter Zijlstra Cc: Frederic Weisbecker , Alan Stern , Arnaldo Carvalho de Melo , Ingo Molnar , Paul Mackerras , Prasad , Roland McGrath , linux-kernel@vger.kernel.org Subject: Re: Q: perf_event && event->owner Message-ID: <20101109165805.GA6971@redhat.com> References: <20101108145647.GA3426@redhat.com> <20101108145754.GB3434@redhat.com> <20101108201108.GA6777@nowhere> <20101109155714.GA1903@redhat.com> <1289321804.2191.57.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1289321804.2191.57.camel@laptop> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/09, Peter Zijlstra wrote: > > On Tue, 2010-11-09 at 16:57 +0100, Oleg Nesterov wrote: > > > > If the creator of perf_event dies, nobody can use its ->perf_event_list > > anyway. What is the point to keep the reference to the dead task_struct > > and preserve this ->perf_event_list? > > But when the owner dies it will close all its fds, which means it will > clear its tsk->perf_event_list, no? (With exception of the case where > the fd was passed through a unix-socket to another process). fork(), pthread_create(). Only __fput() calls ->release, when the last reference to file goes away. And ptrace(), it doesn't use sys_perf_event_open() to create the event. Oleg.