Fix: eliminate timestamp overlap between packets

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

diff --git a/libringbuffer/frontend_internal.h b/libringbuffer/frontend_internal.h
index 4ada183791c2a4f4253bb10baf1cff36b4d97214..8a0f78f32ee774e19e853b3c7c511957ed7adb85 100644 (file)
--- a/libringbuffer/frontend_internal.h
+++ b/libringbuffer/frontend_internal.h
@@ -365,6 +365,13 @@ void lib_ring_buffer_wakeup(struct lttng_ust_lib_ring_buffer *buf,
        }
 }
 
+/*
+ * Receive end of subbuffer TSC as parameter. It has been read in the
+ * space reservation loop of either reserve or switch, which ensures it
+ * progresses monotonically with event records in the buffer. Therefore,
+ * it ensures that the end timestamp of a subbuffer is <= begin
+ * timestamp of the following subbuffers.
+ */
 static inline
 void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config,
                                   struct lttng_ust_lib_ring_buffer *buf,
@@ -372,11 +379,11 @@ void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config
                                   unsigned long offset,
                                   unsigned long commit_count,
                                   unsigned long idx,
-                                  struct lttng_ust_shm_handle *handle)
+                                  struct lttng_ust_shm_handle *handle,
+                                  uint64_t tsc)
 {
        unsigned long old_commit_count = commit_count
                                         - chan->backend.subbuf_size;
-       uint64_t tsc;
 
        /* Check if all commits have been done */
        if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
@@ -422,7 +429,6 @@ void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config
                         * and any other writer trying to access this subbuffer
                         * in this state is required to drop records.
                         */
-                       tsc = config->cb.ring_buffer_clock_read(chan);
                        v_add(config,
                              subbuffer_get_records_count(config,
                                                          &buf->backend,