[tip:perf/core] perf tools: Fix synthesizing fork_event.ppid for non-main thread

[tip-bot for David Ahern]

Commit-ID:  7764a385f60bd200304a33124bdb4e684caeabdf
Gitweb:     http://git.kernel.org/tip/7764a385f60bd200304a33124bdb4e684caeabdf
Author:     David Ahern <david.ahern@xxxxxxxxxx>
AuthorDate: Thu, 9 Apr 2015 12:48:27 -0400
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Fri, 10 Apr 2015 10:10:55 -0300

perf tools: Fix synthesizing fork_event.ppid for non-main thread

Commit ca6c41c59b9 sets the ppid based on what is read from the
/proc/pid/status file when synthesizing fork events.

This is correct thing to do for new processes but not threads of a
process.

Fix ppid for threads to be the main thread when synthesizing fork events
(ie., assume main thread spawned all sub-threads in a process).

Reported-by: Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx>
Signed-off-by: David Ahern <david.ahern@xxxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Acked-by: Don Zickus <dzickus@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1428598107-178999-1-git-send-email-david.ahern@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/event.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 5516236..9d09851 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -183,8 +183,18 @@ static int perf_event__synthesize_fork(struct perf_tool *tool,
 {
 	memset(&event->fork, 0, sizeof(event->fork) + machine->id_hdr_size);
 
-	event->fork.ppid = ppid;
-	event->fork.ptid = ppid;
+	/*
+	 * for main thread set parent to ppid from status file. For other
+	 * threads set parent pid to main thread. ie., assume main thread
+	 * spawns all threads in a process
+	*/
+	if (tgid == pid) {
+		event->fork.ppid = ppid;
+		event->fork.ptid = ppid;
+	} else {
+		event->fork.ppid = tgid;
+		event->fork.ptid = tgid;
+	}
 	event->fork.pid  = tgid;
 	event->fork.tid  = pid;
 	event->fork.header.type = PERF_RECORD_FORK;
--
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