Implement ring buffer clear

[lttng-modules.git] / lib / ringbuffer / frontend_internal.h

diff --git a/lib/ringbuffer/frontend_internal.h b/lib/ringbuffer/frontend_internal.h
index d02a73d32c2a46bc8a26469e1fddb0fb6eb762f1..a1bfe558440c7d8f7f5af4d45395d6047fe334b7 100644 (file)
--- a/lib/ringbuffer/frontend_internal.h
+++ b/lib/ringbuffer/frontend_internal.h
@@ -154,6 +154,8 @@ extern
 void lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf);
 extern
 void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer *buf);
+extern
+void lib_ring_buffer_clear(struct lib_ring_buffer *buf);
 
 /* Buffer write helpers */
 
@@ -185,6 +187,30 @@ void lib_ring_buffer_reserve_push_reader(struct lib_ring_buffer *buf,
                                              consumed_new) != consumed_old));
 }
 
+/*
+ * Move consumed position to the beginning of subbuffer in which the
+ * write offset is.
+ */
+static inline
+void lib_ring_buffer_clear_reader(struct lib_ring_buffer *buf,
+                                 struct channel *chan)
+{
+       const struct lib_ring_buffer_config *config = &chan->backend.config;
+       unsigned long offset, consumed_old, consumed_new;
+
+       do {
+               offset = v_read(config, &buf->offset);
+               consumed_old = atomic_long_read(&buf->consumed);
+               if (unlikely(subbuf_trunc(offset, chan)
+                             - subbuf_trunc(consumed_old, chan)
+                            > 0))
+                       consumed_new = subbuf_trunc(offset, chan);
+               else
+                       return;
+       } while (unlikely(atomic_long_cmpxchg(&buf->consumed, consumed_old,
+                                             consumed_new) != consumed_old));
+}
+
 static inline
 int lib_ring_buffer_pending_data(const struct lib_ring_buffer_config *config,
                                 struct lib_ring_buffer *buf,