From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 10 Dec 2020 15:14:43 +0000 (-0500)
Subject: Fix: event notifier: notification send should be a callback
X-Git-Tag: v2.13.0-rc1~410
X-Git-Url: http://git.lttng.org/?p=lttng-ust.git;a=commitdiff_plain;h=cab88ff8cb13622233f1e0ed338d8d10a229370d

Fix: event notifier: notification send should be a callback

Turn notification send into a callback so probes compiled against
lttng-ust 2.13+ but executed in an environment with lttng-ust 2.12 or
prior don't trigger linker error due to missing
lttng_event_notifier_notification_send symbol.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib51fdc09865f8ae158129417b9e26e86221881b0
---

diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h
index 7e70ea40..98513891 100644
--- a/include/lttng/ust-events.h
+++ b/include/lttng/ust-events.h
@@ -64,6 +64,7 @@ struct lttng_session;
 struct lttng_ust_lib_ring_buffer_ctx;
 struct lttng_ust_context_app;
 struct lttng_event_field;
+struct lttng_event_notifier;
 struct lttng_event_notifier_group;
 
 /*
@@ -515,6 +516,8 @@ struct lttng_event_notifier {
 	int enabled;
 	int registered;			/* has reg'd tracepoint probe */
 	size_t num_captures;		/* Needed to allocate the msgpack array. */
+	void (*notification_send)(struct lttng_event_notifier *event_notifier,
+		const char *stack_data);
 	struct cds_list_head filter_bytecode_runtime_head;
 	struct cds_list_head capture_bytecode_runtime_head;
 	int has_enablers_without_bytecode;
@@ -751,10 +754,6 @@ int lttng_session_disable(struct lttng_session *session);
 int lttng_session_statedump(struct lttng_session *session);
 void lttng_session_destroy(struct lttng_session *session);
 
-void lttng_event_notifier_notification_send(
-		struct lttng_event_notifier *event_notifier,
-		const char *stack_data);
-
 struct lttng_channel *lttng_channel_create(struct lttng_session *session,
 				       const char *transport_name,
 				       void *buf_addr,
diff --git a/include/lttng/ust-tracepoint-event.h b/include/lttng/ust-tracepoint-event.h
index ad159b0d..ef9ea692 100644
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -957,6 +957,7 @@ void __event_notifier_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args))
 		size_t __dynamic_len[__num_fields];			      \
 		char __interpreter_stack_data[2 * sizeof(unsigned long) * __num_fields]; \
 	} __stackvar;							      \
+									      \
 	if (caa_unlikely(!CMM_ACCESS_ONCE(__event_notifier->enabled)))	      \
 		return;							      \
 	if (caa_unlikely(!TP_RCU_LINK_TEST()))				      \
@@ -979,7 +980,7 @@ void __event_notifier_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args))
 		__event_prepare_interpreter_stack__##_provider##___##_name(__stackvar.__interpreter_stack_data, \
 			_TP_ARGS_DATA_VAR(_args));			      \
 									      \
-	lttng_event_notifier_notification_send(__event_notifier,	      \
+	__event_notifier->notification_send(__event_notifier,		      \
 			__stackvar.__interpreter_stack_data);		      \
 }
 
diff --git a/liblttng-ust/lttng-events.c b/liblttng-ust/lttng-events.c
index c80ecbfd..53bb1100 100644
--- a/liblttng-ust/lttng-events.c
+++ b/liblttng-ust/lttng-events.c
@@ -869,6 +869,7 @@ int lttng_event_notifier_create(const struct lttng_event_desc *desc,
 	CDS_INIT_LIST_HEAD(&event_notifier->capture_bytecode_runtime_head);
 	CDS_INIT_LIST_HEAD(&event_notifier->enablers_ref_head);
 	event_notifier->desc = desc;
+	event_notifier->notification_send = lttng_event_notifier_notification_send;
 
 	cds_list_add(&event_notifier->node,
 			&event_notifier_group->event_notifiers_head);
diff --git a/liblttng-ust/lttng-tracer-core.h b/liblttng-ust/lttng-tracer-core.h
index 76f62510..f464d87a 100644
--- a/liblttng-ust/lttng-tracer-core.h
+++ b/liblttng-ust/lttng-tracer-core.h
@@ -84,6 +84,11 @@ extern void (*lttng_ust_liburcu_bp_before_fork)(void);
 extern void (*lttng_ust_liburcu_bp_after_fork_parent)(void);
 extern void (*lttng_ust_liburcu_bp_after_fork_child)(void);
 
+LTTNG_HIDDEN
+void lttng_event_notifier_notification_send(
+		struct lttng_event_notifier *event_notifier,
+		const char *stack_data);
+
 #ifdef LTTNG_UST_HAVE_PERF_EVENT
 void lttng_ust_fixup_perf_counter_tls(void);
 void lttng_perf_lock(void);