Commit f3ae75de authored Jan 08, 2014 by Stephane Eranian Committed by Ingo Molnar Jan 12, 2014

perf/x86: Fix active_entry initialization



This patch fixes a problem with the initialization of the
struct perf_event active_entry field. It is defined inside
an anonymous union and was initialized in perf_event_alloc()
using INIT_LIST_HEAD(). However at that time, we do not know
whether the event is going to use active_entry or hlist_entry (SW).
Or at last, we don't want to make that determination there.
The problem is that hlist and list_head are not initialized
the same way. One is okay with NULL (from kzmalloc), the other
needs to pointers to point to self.

This patch resolves this problem by dropping the union.
This will avoid problems later on, if someone starts using
active_entry or hlist_entry without verifying that they
actually overlap. This also solves the initialization
problem.

Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: ak@linux.intel.com
Cc: acme@redhat.com
Cc: jolsa@redhat.com
Cc: zheng.z.yan@intel.com
Cc: bp@alien8.de
Cc: vincent.weaver@maine.edu
Cc: maria.n.dimakopoulou@gmail.com
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1389176153-3128-2-git-send-email-eranian@google.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent fa6e8e5f

include/linux/perf_event.h

+2 −4

Original line number	Diff line number	Diff line
		@@ -319,10 +319,8 @@ struct perf_event {
		*/
		struct list_head migrate_entry;

		union {
		struct hlist_node hlist_entry;
		struct list_head active_entry;
		};
		int nr_siblings;
		int group_flags;
		struct perf_event *group_leader;

kernel/events/core.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -6670,6 +6670,8 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
		INIT_LIST_HEAD(&event->sibling_list);
		INIT_LIST_HEAD(&event->rb_entry);
		INIT_LIST_HEAD(&event->active_entry);
		INIT_HLIST_NODE(&event->hlist_entry);


		init_waitqueue_head(&event->waitq);
		init_irq_work(&event->pending, perf_pending_event);

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