ustctl: Implement ring buffer clear

[lttng-ust.git] / libringbuffer / frontend_internal.h

diff --git a/libringbuffer/frontend_internal.h b/libringbuffer/frontend_internal.h
index 323a8df7f98cd7e5d3aba69302c6c291799b8bbd..4ad921ec0ec8263086cddbf1c11044110dc672f6 100644 (file)
--- a/libringbuffer/frontend_internal.h
+++ b/libringbuffer/frontend_internal.h
@@ -205,6 +205,32 @@ void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf,
                                              consumed_new) != consumed_old));
 }
 
+static inline
+void lib_ring_buffer_clear_reader(struct lttng_ust_lib_ring_buffer *buf,
+                                 struct lttng_ust_shm_handle *handle)
+{
+       struct channel *chan;
+       const struct lttng_ust_lib_ring_buffer_config *config;
+       unsigned long offset, consumed_old, consumed_new;
+
+       chan = shmp(handle, buf->backend.chan);
+       if (!chan)
+               return;
+       config = &chan->backend.config;
+
+       do {
+               offset = v_read(config, &buf->offset);
+               consumed_old = uatomic_read(&buf->consumed);
+               if (caa_unlikely(subbuf_trunc(offset, chan)
+                             - subbuf_trunc(consumed_old, chan)
+                            > 0))
+                       consumed_new = subbuf_trunc(offset, chan);
+               else
+                       return;
+       } while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old,
+                                             consumed_new) != consumed_old));
+}
+
 static inline
 int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config,
                                 struct lttng_ust_lib_ring_buffer *buf,