linux-kernel - [PATCH 1/3] perf tools: Don't stop synthesizing threads when one vanishes

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Date:	Thu, 25 Oct 2012 17:47:43 -0200
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: [PATCH 1/3] perf tools: Don't stop synthesizing threads when one vanishes

From: Arnaldo Carvalho de Melo <acme@...hat.com>

The perf_event__synthesize_threads routine synthesizes all the existing
threads in the system, because we don't have any kernel facilities to
ask for PERF_RECORD_{FORK,MMAP,COMM} for existing threads.

It was returning an error as soon as one thread couldn't be synthesized,
which is a bit extreme when, for instance, a forkish workload is
running, like a kernel compile.

Cc: David Ahern <dsahern@...il.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Mike Galbraith <efault@....de>
Cc: Namhyung Kim <namhyung@...il.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Link: http://lkml.kernel.org/n/tip-i7oas1eodpoer2bx38fwyasv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/event.c |   13 ++++++-------
 1 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 0ae444e..ca9ca28 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -405,16 +405,15 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
 
 		if (*end) /* only interested in proper numerical dirents */
 			continue;
-
-		if (__event__synthesize_thread(comm_event, mmap_event, pid, 1,
-					   process, tool, machine) != 0) {
-			err = -1;
-			goto out_closedir;
-		}
+		/*
+ 		 * We may race with exiting thread, so don't stop just because
+ 		 * one thread couldn't be synthesized.
+ 		 */
+		__event__synthesize_thread(comm_event, mmap_event, pid, 1,
+					   process, tool, machine);
 	}
 
 	err = 0;
-out_closedir:
 	closedir(proc);
 out_free_mmap:
 	free(mmap_event);
-- 
1.7.1

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