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authorSteven Rostedt <srostedt@redhat.com>2009-04-02 00:09:41 -0400
committerIngo Molnar <mingo@elte.hu>2009-04-14 00:00:53 +0200
commitfa1b47dd85453ec7d4bcfe4aa4a2d172ba452fc3 (patch)
tree3e5f14cccd9e4ec772310c1b2792b6f4b84bf7cb /include
parente45f2e2bd298e1ff687448e5fd15a3588b5807ec (diff)
ring-buffer: add ring_buffer_discard_commit
The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include')
-rw-r--r--include/linux/ring_buffer.h29
1 files changed, 29 insertions, 0 deletions
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index e1b7b217388..f0aa486d131 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -68,9 +68,38 @@ ring_buffer_event_time_delta(struct ring_buffer_event *event)
return event->time_delta;
}
+/*
+ * ring_buffer_event_discard can discard any event in the ring buffer.
+ * it is up to the caller to protect against a reader from
+ * consuming it or a writer from wrapping and replacing it.
+ *
+ * No external protection is needed if this is called before
+ * the event is commited. But in that case it would be better to
+ * use ring_buffer_discard_commit.
+ *
+ * Note, if an event that has not been committed is discarded
+ * with ring_buffer_event_discard, it must still be committed.
+ */
void ring_buffer_event_discard(struct ring_buffer_event *event);
/*
+ * ring_buffer_discard_commit will remove an event that has not
+ * ben committed yet. If this is used, then ring_buffer_unlock_commit
+ * must not be called on the discarded event. This function
+ * will try to remove the event from the ring buffer completely
+ * if another event has not been written after it.
+ *
+ * Example use:
+ *
+ * if (some_condition)
+ * ring_buffer_discard_commit(buffer, event);
+ * else
+ * ring_buffer_unlock_commit(buffer, event);
+ */
+void ring_buffer_discard_commit(struct ring_buffer *buffer,
+ struct ring_buffer_event *event);
+
+/*
* size is in bytes for each per CPU buffer.
*/
struct ring_buffer *