[lttng-dev] [PATCH lttng-ust v2 1/6] Remove duplicate provider name checks

[Francis Deslauriers]

From: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>

It's now possible to register a probe provider with a name that has
already been registered. This is useful when wanting to load a new
version of a shared library on a already running process.

Changes are necessary in the lttng-session daemon to support cases where
the newly register event has a different probe payload.

Taking a simple case where a probe provider is registered twice, the
tracepoint call site will have two probes registered to it and thus will
generate two events in the trace.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Signed-off-by: Francis Deslauriers <francis.deslauriers at efficios.com>
---
 include/lttng/ust-tracepoint-event.h |  2 +-
 liblttng-ust/lttng-events.c          | 11 -----------
 liblttng-ust/lttng-probes.c          | 23 +----------------------
 3 files changed, 2 insertions(+), 34 deletions(-)

diff --git a/include/lttng/ust-tracepoint-event.h b/include/lttng/ust-tracepoint-event.h
index 15399c7..ec292d2 100644
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -1007,7 +1007,7 @@ _TP_COMBINE_TOKENS(__lttng_events_init__, TRACEPOINT_PROVIDER)(void)
 	_TP_COMBINE_TOKENS(__tracepoint_provider_check_, TRACEPOINT_PROVIDER)();
 	ret = lttng_probe_register(&_TP_COMBINE_TOKENS(__probe_desc___, TRACEPOINT_PROVIDER));
 	if (ret) {
-		fprintf(stderr, "LTTng-UST: Error (%d) while registering tracepoint probe. Duplicate registration of tracepoint probes having the same name is not allowed.\n", ret);
+		fprintf(stderr, "LTTng-UST: Error (%d) while registering tracepoint probe.\n", ret);
 		abort();
 	}
 }
diff --git a/liblttng-ust/lttng-events.c b/liblttng-ust/lttng-events.c
index bfdae4f..f4a7ccc 100644
--- a/liblttng-ust/lttng-events.c
+++ b/liblttng-ust/lttng-events.c
@@ -537,7 +537,6 @@ int lttng_event_create(const struct lttng_event_desc *desc,
 	struct lttng_event *event;
 	struct lttng_session *session = chan->session;
 	struct cds_hlist_head *head;
-	struct cds_hlist_node *node;
 	int ret = 0;
 	size_t name_len = strlen(event_name);
 	uint32_t hash;
@@ -546,15 +545,6 @@ int lttng_event_create(const struct lttng_event_desc *desc,
 
 	hash = jhash(event_name, name_len, 0);
 	head = &chan->session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
-	cds_hlist_for_each_entry(event, node, head, hlist) {
-		assert(event->desc);
-		if (!strncmp(event->desc->name, desc->name,
-					LTTNG_UST_SYM_NAME_LEN - 1)
-				&& chan == event->chan) {
-			ret = -EEXIST;
-			goto exist;
-		}
-	}
 
 	notify_socket = lttng_get_notify_socket(session->owner);
 	if (notify_socket < 0) {
@@ -623,7 +613,6 @@ sessiond_register_error:
 cache_error:
 create_enum_error:
 socket_error:
-exist:
 	return ret;
 }
 
diff --git a/liblttng-ust/lttng-probes.c b/liblttng-ust/lttng-probes.c
index 390265a..a09497f 100644
--- a/liblttng-ust/lttng-probes.c
+++ b/liblttng-ust/lttng-probes.c
@@ -148,20 +148,6 @@ struct cds_list_head *lttng_get_probe_list_head(void)
 }
 
 static
-const struct lttng_probe_desc *find_provider(const char *provider)
-{
-	struct lttng_probe_desc *iter;
-	struct cds_list_head *probe_list;
-
-	probe_list = lttng_get_probe_list_head();
-	cds_list_for_each_entry(iter, probe_list, head) {
-		if (!strcmp(iter->provider, provider))
-			return iter;
-	}
-	return NULL;
-}
-
-static
 int check_provider_version(struct lttng_probe_desc *desc)
 {
 	/*
@@ -206,13 +192,6 @@ int lttng_probe_register(struct lttng_probe_desc *desc)
 
 	ust_lock_nocheck();
 
-	/*
-	 * Check if the provider has already been registered.
-	 */
-	if (find_provider(desc->provider)) {
-		ret = -EEXIST;
-		goto end;
-	}
 	cds_list_add(&desc->lazy_init_head, &lazy_probe_init);
 	desc->lazy = 1;
 	DBG("adding probe %s containing %u events to lazy registration list",
@@ -224,7 +203,7 @@ int lttng_probe_register(struct lttng_probe_desc *desc)
 	 */
 	if (lttng_session_active())
 		fixup_lazy_probes();
-end:
+
 	ust_unlock();
 	return ret;
 }
-- 
2.7.4