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Subject[PATCH v6 1/4] perf: add active_entry list head to struct perf_event
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This patch adds a new field to the struct perf_event.
It is intended to be used to chain events which are
active (enabled). It helps in the hardware layer
for PMUs which do not have actual counter restrictions, i.e.,
free running read-only counters. Active events are chained
as opposed to being tracked via the counter they use.

To save space we use a union with hlist_entry as both
are mutually exclusive (suggested by Jiri Olsa).

Signed-off-by: Stephane Eranian <eranian@google.com>
---
include/linux/perf_event.h | 5 ++++-
kernel/events/core.c | 1 +
2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 2e069d1..8f4a70f 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -319,7 +319,10 @@ struct perf_event {
*/
struct list_head migrate_entry;

- struct hlist_node hlist_entry;
+ union {
+ struct hlist_node hlist_entry;
+ struct list_head active_entry;
+ };
int nr_siblings;
int group_flags;
struct perf_event *group_leader;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4dc078d..90dca5c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6663,6 +6663,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
INIT_LIST_HEAD(&event->event_entry);
INIT_LIST_HEAD(&event->sibling_list);
INIT_LIST_HEAD(&event->rb_entry);
+ INIT_LIST_HEAD(&event->active_entry);

init_waitqueue_head(&event->waitq);
init_irq_work(&event->pending, perf_pending_event);
--
1.7.9.5


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