linux-kernel - Re: perf tip: fails to convert comm

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Message-ID: <20131116010207.GA18855@localhost.localdomain>
Date:	Sat, 16 Nov 2013 02:02:09 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	David Ahern <dsahern@...il.com>
Cc:	Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: perf tip: fails to convert comm

On Fri, Nov 15, 2013 at 09:29:51AM -0700, David Ahern wrote:
> HI Frederic:
> 
> On 11/13/13, 11:03 AM, Frederic Weisbecker wrote:
> >
> >I see. I can reproduce, I'll check and see what happens. It would be nice if
> >we could have an option to dump internal perf events like comm events as well
> >in the perf script stream.
> 
> Any progress on a solution? This is a regression in 3.13.

So the problem is that when a thread overrides its default ":%pid" comm, we forget
to tag the thread comm as overriden. Hence, this overriden comm is not inherited on
future forks.

So here is a fix. Tell me if you see more issue, I'll cook a proper changelog and
resend if everyting looks good.

Thanks.

diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index cd8e2f5..49eaf1d 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -70,14 +70,13 @@ int thread__set_comm(struct thread *thread, const char *str, u64 timestamp)
 	/* Override latest entry if it had no specific time coverage */
 	if (!curr->start) {
 		comm__override(curr, str, timestamp);
-		return 0;
+	} else {
+		new = comm__new(str, timestamp);
+		if (!new)
+			return -ENOMEM;
+		list_add(&new->list, &thread->comm_list);
 	}
 
-	new = comm__new(str, timestamp);
-	if (!new)
-		return -ENOMEM;
-
-	list_add(&new->list, &thread->comm_list);
 	thread->comm_set = true;
 
 	return 0;
--
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