linux-kernel - Re: [PATCH 1/2] perf: Reset detached siblings' group

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Date:	Mon, 11 Mar 2013 20:51:31 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Namhyung Kim <namhyung.kim@....com>,
	Jiri Olsa <jolsa@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 1/2] perf: Reset detached siblings' group_flags

While looking at the code again, I found that the detached siblings
should call perf_event__header_size() for themselves in the loop since
after moving them to the list the previous leader will have empty
sibling_list.  Something like below is needed IMHO:


diff --git a/kernel/events/core.c b/kernel/events/core.c
index dc96fee942a6..53ac21cc4012 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1100,6 +1100,13 @@ static void perf_group_detach(struct perf_event *event)
 
 		/* Inherit group flags from the previous leader */
 		sibling->group_flags = event->group_flags;
+
+		/*
+		 * The leader will forget about siblings from now on.
+		 * So below loop to update header size of each sibling won't
+		 * work for this case. Do it directly.
+		 */
+		perf_event__header_size(sibling);
 	}
 
 out:
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