[PATCH 02/16] perf, mmap: Factor out try_get_event()/put_event()

Jean Pihet
2014-04-07T15:05:07Z

From: Robert Richter <robert.richter@linaro.org>

Implement try_get_event() as counter part to put_event(). Put both in
internal.h to make it available to other perf files.

Signed-off-by: Robert Richter <robert.richter@linaro.org>
Signed-off-by: Robert Richter <rric@kernel.org>
Signed-off-by: Jean Pihet <jean.pihet@linaro.org>
---
kernel/events/core.c | 9 +++------
kernel/events/internal.h | 12 ++++++++++++
2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 8867236..5eaba42 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3311,13 +3311,10 @@ EXPORT_SYMBOL_GPL(perf_event_release_kernel);
/*
* Called when the last reference to the file is gone.
*/
-static void put_event(struct perf_event *event)
+void __put_event(struct perf_event *event)
{
struct task_struct *owner;

- if (!atomic_long_dec_and_test(&event->refcount))
- return;
-
rcu_read_lock();
owner = ACCESS_ONCE(event->owner);
/*
@@ -3884,7 +3881,7 @@ static void ring_buffer_detach_all(struct ring_buffer *rb)
again:
rcu_read_lock();
list_for_each_entry_rcu(event, &rb->event_list, rb_entry) {
- if (!atomic_long_inc_not_zero(&event->refcount)) {
+ if (!try_get_event(event)) {
/*
* This event is en-route to free_event() which will
* detach it and remove it from the list.
@@ -7606,7 +7603,7 @@ inherit_event(struct perf_event *parent_event,
if (IS_ERR(child_event))
return child_event;

- if (!atomic_long_inc_not_zero(&parent_event->refcount)) {
+ if (!try_get_event(parent_event)) {
free_event(child_event);
return NULL;
}
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 569b2187..3bd89d4 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -195,4 +195,16 @@ static inline bool arch_perf_have_user_stack_dump(void)
#define perf_user_stack_pointer(regs) 0
#endif /* CONFIG_HAVE_PERF_USER_STACK_DUMP */

+static inline bool try_get_event(struct perf_event *event)
+{
+ return atomic_long_inc_not_zero(&event->refcount) != 0;
+}
+extern void __put_event(struct perf_event *event);
+static inline void put_event(struct perf_event *event)
+{
+ if (!atomic_long_dec_and_test(&event->refcount))
+ return;
+ __put_event(event);
+}
+
#endif /* _KERNEL_EVENTS_INTERNAL_H */
--
1.7.11.7