From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751821AbaIFUj5 (ORCPT ); Sat, 6 Sep 2014 16:39:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5495 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750826AbaIFUj4 (ORCPT ); Sat, 6 Sep 2014 16:39:56 -0400 Date: Sat, 6 Sep 2014 22:39:15 +0200 From: Jiri Olsa To: Arnaldo Carvalho de Melo Cc: Adrian Hunter , linux-kernel@vger.kernel.org, David Ahern , Don Zickus , Frederic Weisbecker , Mike Galbraith , Namhyung Kim , Paul Mackerras , Peter Zijlstra , Stephane Eranian Subject: Re: [PATCH 04/10] perf record: Filter out POLLHUP'ed file descriptors Message-ID: <20140906203915.GA9843@krava.brq.redhat.com> References: <1409781604-16778-1-git-send-email-acme@kernel.org> <1409781604-16778-5-git-send-email-acme@kernel.org> <54085BC8.40403@intel.com> <20140904151902.GE2997@kernel.org> <54097793.4050201@intel.com> <20140905140756.GD30520@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140905140756.GD30520@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 05, 2014 at 11:07:56AM -0300, Arnaldo Carvalho de Melo wrote: > Em Fri, Sep 05, 2014 at 11:42:59AM +0300, Adrian Hunter escreveu: > > On 09/04/2014 06:19 PM, Arnaldo Carvalho de Melo wrote: > > > Em Thu, Sep 04, 2014 at 03:32:08PM +0300, Adrian Hunter escreveu: > > No I was meaning something different. For example, 'perf record' opens an > > event for 2 processes per-cpu and gets 4 file descriptors: > > > task1 task2 > > cpu0 fd0 fd1 > > cpu1 fd2 fd3 > > > Now, perf record will mmap fd0 and fd2 and set-output fd1->fd0 > > and fd3->fd2. > > > pollfds includes only fd0 and fd2. > > > But if task2 exits, the POLLHUP will appear on fd1 and fd3. > > So? We are not interested in fd1 and fd3, since all our reading is done > on fd0 and fd2 mmaps, no? hm, what if task1 (fd0, fd2) exits first.. perf record will exit, but it still has to read task2..? > > I.e. when we ask the kernel to point fd B to fd A's mmap (what you > called set-output) and fd B inserts an event into fd A's mmap ring > buffer, we get fd A poll return as POLLRD, no? > > Have to check... Otherwise we would have to poll all fds all the time, > not just the ones mmaping, right? > > > I think Jiri's patchset changed pollfds to include all fds for that reason. hm, I did not think of that.. ;-) I needed more grained feedback for future features like cpu hotplug > > It did? I have to look again, probably went together with other changes, > has it? it was done by replacing 'int' with 'struct poll_item' for evsel::fd xyarray jirka