Fix: backward compatibility with UST 2.0 app probes

[lttng-ust.git] / include / lttng / ringbuffer-config.h

diff --git a/include/lttng/ringbuffer-config.h b/include/lttng/ringbuffer-config.h
index 650b56b250db4dbb6d2889bff659c74fe1c20970..174906cbafcdea9469601ba39a996bde3f2ecc26 100644 (file)
--- a/include/lttng/ringbuffer-config.h
+++ b/include/lttng/ringbuffer-config.h
@@ -188,6 +188,10 @@ struct lttng_ust_lib_ring_buffer_config {
  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
  * lib_ring_buffer_write().
+ *
+ * IMPORTANT: this structure is part of the ABI between the probe and
+ * UST. Fields need to be only added at the end, never reordered, never
+ * removed.
  */
 #define LTTNG_UST_RING_BUFFER_CTX_PADDING      24
 struct lttng_ust_lib_ring_buffer_ctx {