From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754811AbdCGIMV (ORCPT ); Tue, 7 Mar 2017 03:12:21 -0500 Received: from terminus.zytor.com ([65.50.211.136]:33602 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750824AbdCGIMO (ORCPT ); Tue, 7 Mar 2017 03:12:14 -0500 Date: Tue, 7 Mar 2017 00:02:57 -0800 From: tip-bot for Arnaldo Carvalho de Melo Message-ID: Cc: acme@redhat.com, dsahern@gmail.com, mingo@kernel.org, elena.reshetova@intel.com, tglx@linutronix.de, wangnan0@huawei.com, adrian.hunter@intel.com, linux-kernel@vger.kernel.org, jolsa@kernel.org, peterz@infradead.org, namhyung@kernel.org, hpa@zytor.com Reply-To: adrian.hunter@intel.com, linux-kernel@vger.kernel.org, peterz@infradead.org, jolsa@kernel.org, namhyung@kernel.org, hpa@zytor.com, acme@redhat.com, dsahern@gmail.com, mingo@kernel.org, elena.reshetova@intel.com, tglx@linutronix.de, wangnan0@huawei.com In-Reply-To: <20170223162344.GD3595@kernel.org> References: <20170223162344.GD3595@kernel.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf evlist: Clarify a bit the use of perf_mmap->refcnt Git-Commit-ID: 4738ca30b4a7a113084d7863846175094f95c62f X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 4738ca30b4a7a113084d7863846175094f95c62f Gitweb: http://git.kernel.org/tip/4738ca30b4a7a113084d7863846175094f95c62f Author: Arnaldo Carvalho de Melo AuthorDate: Thu, 23 Feb 2017 13:24:34 -0300 Committer: Arnaldo Carvalho de Melo CommitDate: Fri, 3 Mar 2017 19:07:16 -0300 perf evlist: Clarify a bit the use of perf_mmap->refcnt This is an odd refcount use case, so add some more comments to help understand that when it hits zero it really means that the mmap()ed area (on a perf_event_open() returned fd) has been munmap()ed. Cc: Adrian Hunter Cc: David Ahern Cc: Elena Reshetova Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Wang Nan Link: http://lkml.kernel.org/r/20170223162344.GD3595@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/evlist.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 564b924..50420cd 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -974,8 +974,19 @@ static struct perf_mmap *perf_evlist__alloc_mmap(struct perf_evlist *evlist) if (!map) return NULL; - for (i = 0; i < evlist->nr_mmaps; i++) + for (i = 0; i < evlist->nr_mmaps; i++) { map[i].fd = -1; + /* + * When the perf_mmap() call is made we grab one refcount, plus + * one extra to let perf_evlist__mmap_consume() get the last + * events after all real references (perf_mmap__get()) are + * dropped. + * + * Each PERF_EVENT_IOC_SET_OUTPUT points to this mmap and + * thus does perf_mmap__get() on it. + */ + refcount_set(&map[i].refcnt, 0); + } return map; }