linux-kernel - [tip:perf/core] perf evlist: We need to poll all event file descriptors

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Date:	Fri, 26 Sep 2014 02:20:08 -0700
From:	tip-bot for Arnaldo Carvalho de Melo <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, eranian@...gle.com, paulus@...ba.org,
	acme@...hat.com, hpa@...or.com, mingo@...nel.org,
	peterz@...radead.org, efault@....de, namhyung@...nel.org,
	jolsa@...hat.com, fweisbec@...il.com, adrian.hunter@...el.com,
	dsahern@...il.com, tglx@...utronix.de, dzickus@...hat.com
Subject: [tip:perf/core] perf evlist:
  We need to poll all event file descriptors

Commit-ID:  033fa713db66b96d5779e6a93d50ff821bc1abd2
Gitweb:     http://git.kernel.org/tip/033fa713db66b96d5779e6a93d50ff821bc1abd2
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Mon, 8 Sep 2014 12:55:12 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Thu, 25 Sep 2014 16:46:54 -0300

perf evlist: We need to poll all event file descriptors

Because we want to notice when they get POLLHUP'ed, so that we can
figure out when all threads exited in a workload being monitored.

We can't just monitor the fds that were mmaped, we need to notice when
all the fds that were PERF_EVENT_IOC_SET_OUTPUT'ed too, because the mmap
stays even after the fd that originally was used to do the mmap call
went away, its only when all the set-output fds for a mmap are gone that
the mmap is.

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Don Zickus <dzickus@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Mike Galbraith <efault@....de>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Link: http://lkml.kernel.org/r/20140908151016.GH17728@krava.brq.redhat.com
Link: http://lkml.kernel.org/n/tip-24omlq5asrfg4uo3muuzn2bl@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/evlist.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 502cd11..6b13bfa 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -717,8 +717,6 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
 		evlist->mmap[idx].base = NULL;
 		return -1;
 	}
-
-	perf_evlist__add_pollfd(evlist, fd);
 	return 0;
 }
 
@@ -745,6 +743,8 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
 				return -1;
 		}
 
+		perf_evlist__add_pollfd(evlist, fd);
+
 		if ((evsel->attr.read_format & PERF_FORMAT_ID) &&
 		    perf_evlist__id_add_fd(evlist, evsel, cpu, thread, fd) < 0)
 			return -1;
--
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