X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=ltt-ring-buffer-client.h;h=904c42eb466b68e8745f1108ad50922460ba4980;hb=fcf745787bc83653284a78ff9846f2d75ca35a65;hp=974a696f704465eaa6765f6befe2ba506321d817;hpb=eb9a7857efa6d55e347b81383a7948d72214e574;p=lttng-modules.git

diff --git a/ltt-ring-buffer-client.h b/ltt-ring-buffer-client.h
index 974a696f..904c42eb 100644
--- a/ltt-ring-buffer-client.h
+++ b/ltt-ring-buffer-client.h
@@ -22,6 +22,14 @@
  * you ever add/remove a field from this header. Packed attribute is not used
  * because gcc generates poor code on at least powerpc and mips. Don't ever
  * let gcc add padding between the structure elements.
+ *
+ * The guarantee we have with timestamps is that all the events in a
+ * packet are included (inclusive) within the begin/end timestamps of
+ * the packet. Another guarantee we have is that the "timestamp begin",
+ * as well as the event timestamps, are monotonically increasing (never
+ * decrease) when moving forward in a stream (physically). But this
+ * guarantee does not apply to "timestamp end", because it is sampled at
+ * commit time, which is not ordered with respect to space reservation.
  */
 
 struct packet_header {
@@ -198,8 +206,8 @@ void ltt_write_event_header(const struct lib_ring_buffer_config *config,
 		WARN_ON_ONCE(1);
 	}
 
-	ctx_record(ctx, ltt_chan, event->ctx);
 	ctx_record(ctx, ltt_chan, ltt_chan->ctx);
+	ctx_record(ctx, ltt_chan, event->ctx);
 
 	return;
 
@@ -261,8 +269,8 @@ void ltt_write_event_header_slow(const struct lib_ring_buffer_config *config,
 	default:
 		WARN_ON_ONCE(1);
 	}
-	ctx_record(ctx, ltt_chan, event->ctx);
 	ctx_record(ctx, ltt_chan, ltt_chan->ctx);
+	ctx_record(ctx, ltt_chan, event->ctx);
 }
 
 static const struct lib_ring_buffer_config client_config;