linux-kernel - [PATCH 3.2 110/126] perf: Fix perf_event_for

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Message-ID: <lsq.1487198494.140328748@decadent.org.uk>
Date:   Wed, 15 Feb 2017 22:41:34 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Ingo Molnar" <mingo@...nel.org>,
        "Michael Ellerman" <michael@...erman.id.au>,
        "Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Subject: [PATCH 3.2 110/126] perf: Fix perf_event_for_each() to use sibling

3.2.85-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Ellerman <michael@...erman.id.au>

commit 724b6daa13e100067c30cfc4d1ad06629609dc4e upstream.

In perf_event_for_each() we call a function on an event, and then
iterate over the siblings of the event.

However we don't call the function on the siblings, we call it
repeatedly on the original event - it seems "obvious" that we should
be calling it with sibling as the argument.

It looks like this broke in commit 75f937f24bd9 ("Fix ctx->mutex
vs counter->mutex inversion").

The only effect of the bug is that the PERF_IOC_FLAG_GROUP parameter
to the ioctls doesn't work.

Signed-off-by: Michael Ellerman <michael@...erman.id.au>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/1334109253-31329-1-git-send-email-michael@ellerman.id.au
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3326,7 +3326,7 @@ static void perf_event_for_each(struct p
 	perf_event_for_each_child(event, func);
 	func(event);
 	list_for_each_entry(sibling, &event->sibling_list, group_entry)
-		perf_event_for_each_child(event, func);
+		perf_event_for_each_child(sibling, func);
 	mutex_unlock(&ctx->mutex);
 }