[PATCH 01/16] perf, mmap: Factor out ring_buffer_detach_all()

Jean Pihet
2014-04-07T15:12:50Z

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

Factor out a function to detach all events from a ringbuffer. No
functional changes.

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 | 82 ++++++++++++++++++++++++++++------------------------
1 file changed, 44 insertions(+), 38 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 661951a..8867236 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3878,6 +3878,49 @@ static void ring_buffer_detach(struct perf_event *event, struct ring_buffer *rb)
spin_unlock_irqrestore(&rb->event_lock, flags);
}

+static void ring_buffer_detach_all(struct ring_buffer *rb)
+{
+ struct perf_event *event;
+again:
+ rcu_read_lock();
+ list_for_each_entry_rcu(event, &rb->event_list, rb_entry) {
+ if (!atomic_long_inc_not_zero(&event->refcount)) {
+ /*
+ * This event is en-route to free_event() which will
+ * detach it and remove it from the list.
+ */
+ continue;
+ }
+ rcu_read_unlock();
+
+ mutex_lock(&event->mmap_mutex);
+ /*
+ * Check we didn't race with perf_event_set_output() which can
+ * swizzle the rb from under us while we were waiting to
+ * acquire mmap_mutex.
+ *
+ * If we find a different rb; ignore this event, a next
+ * iteration will no longer find it on the list. We have to
+ * still restart the iteration to make sure we're not now
+ * iterating the wrong list.
+ */
+ if (event->rb == rb) {
+ rcu_assign_pointer(event->rb, NULL);
+ ring_buffer_detach(event, rb);
+ ring_buffer_put(rb); /* can't be last, we still have one */
+ }
+ mutex_unlock(&event->mmap_mutex);
+ put_event(event);
+
+ /*
+ * Restart the iteration; either we're on the wrong list or
+ * destroyed its integrity by doing a deletion.
+ */
+ goto again;
+ }
+ rcu_read_unlock();
+}
+
static void ring_buffer_wakeup(struct perf_event *event)
{
struct ring_buffer *rb;
@@ -3970,44 +4013,7 @@ static void perf_mmap_close(struct vm_area_struct *vma)
* into the now unreachable buffer. Somewhat complicated by the
* fact that rb::event_lock otherwise nests inside mmap_mutex.
*/
-again:
- rcu_read_lock();
- list_for_each_entry_rcu(event, &rb->event_list, rb_entry) {
- if (!atomic_long_inc_not_zero(&event->refcount)) {
- /*
- * This event is en-route to free_event() which will
- * detach it and remove it from the list.
- */
- continue;
- }
- rcu_read_unlock();
-
- mutex_lock(&event->mmap_mutex);
- /*
- * Check we didn't race with perf_event_set_output() which can
- * swizzle the rb from under us while we were waiting to
- * acquire mmap_mutex.
- *
- * If we find a different rb; ignore this event, a next
- * iteration will no longer find it on the list. We have to
- * still restart the iteration to make sure we're not now
- * iterating the wrong list.
- */
- if (event->rb == rb) {
- rcu_assign_pointer(event->rb, NULL);
- ring_buffer_detach(event, rb);
- ring_buffer_put(rb); /* can't be last, we still have one */
- }
- mutex_unlock(&event->mmap_mutex);
- put_event(event);
-
- /*
- * Restart the iteration; either we're on the wrong list or
- * destroyed its integrity by doing a deletion.
- */
- goto again;
- }
- rcu_read_unlock();
+ ring_buffer_detach_all(rb);

/*
* It could be there's still a few 0-ref events on the list; they'll
--
1.7.11.7