[PATCH 1/1] perf tools: Don't use parent comm if not set at fork time

[Arnaldo Carvalho de Melo]

From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

As the parent comm then is worthless, confusing users about the thread where
the sample really happened, leading to think that the sample happened in the
parent, not where it really happened, in the children of a thread for which a
PERF_RECORD_COMM event was not received.

Cc: FrÃdÃric Weisbecker <fweisbec@xxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/thread.c |   18 ++++++++++++------
 tools/perf/util/thread.h |    1 +
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 634b7f7..9e8995e 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -36,7 +36,10 @@ int thread__set_comm(struct thread *self, const char *comm)
 	if (self->comm)
 		free(self->comm);
 	self->comm = strdup(comm);
-	return self->comm ? 0 : -ENOMEM;
+	if (self->comm == NULL)
+		return -ENOMEM;
+	self->comm_set = true;
+	return 0;
 }
 
 int thread__comm_len(struct thread *self)
@@ -255,11 +258,14 @@ int thread__fork(struct thread *self, struct thread *parent)
 {
 	int i;
 
-	if (self->comm)
-		free(self->comm);
-	self->comm = strdup(parent->comm);
-	if (!self->comm)
-		return -ENOMEM;
+	if (parent->comm_set) {
+		if (self->comm)
+			free(self->comm);
+		self->comm = strdup(parent->comm);
+		if (!self->comm)
+			return -ENOMEM;
+		self->comm_set = true;
+	}
 
 	for (i = 0; i < MAP__NR_TYPES; ++i)
 		if (map_groups__clone(&self->mg, &parent->mg, i) < 0)
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 56f317b..0a28f39 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -15,6 +15,7 @@ struct thread {
 	struct map_groups	mg;
 	pid_t			pid;
 	char			shortname[3];
+	bool			comm_set;
 	char			*comm;
 	int			comm_len;
 };
-- 
1.5.5.1

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