X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=liblttng-ust%2Ftracepoint.c;h=00c471969b4394f16b9ec2e13bb520e10e78fe4b;hb=d6297168f9042cdc550507bb5e97cee7037c34d3;hp=7bb38fa9ec307f9b1eb85670c7b90a456e9bce3d;hpb=5e6df7eabfed640cc83d227ae8bed3de75a56694;p=lttng-ust.git

diff --git a/liblttng-ust/tracepoint.c b/liblttng-ust/tracepoint.c
index 7bb38fa9..00c47196 100644
--- a/liblttng-ust/tracepoint.c
+++ b/liblttng-ust/tracepoint.c
@@ -95,6 +95,7 @@ struct tracepoint_entry {
 	struct cds_hlist_node hlist;
 	struct tracepoint_probe *probes;
 	int refcount;	/* Number of times armed. 0 if disarmed. */
+	int callsite_refcount;	/* how many libs use this tracepoint */
 	const char *signature;
 	char name[0];
 };
@@ -295,6 +296,7 @@ static struct tracepoint_entry *add_tracepoint(const char *name,
 	e->name[name_len] = '\0';
 	e->probes = NULL;
 	e->refcount = 0;
+	e->callsite_refcount = 0;
 	e->signature = signature;
 	cds_hlist_add_head(&e->hlist, head);
 	return e;
@@ -310,41 +312,6 @@ static void remove_tracepoint(struct tracepoint_entry *e)
 	free(e);
 }
 
-/*
- * Add the callsite to the callsite hash table. Must be called with
- * tracepoint mutex held.
- */
-static void add_callsite(struct tracepoint *tp)
-{
-	struct cds_hlist_head *head;
-	struct callsite_entry *e;
-	const char *name = tp->name;
-	size_t name_len = strlen(name);
-	uint32_t hash;
-
-	if (name_len > LTTNG_UST_SYM_NAME_LEN - 1) {
-		WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1);
-		name_len = LTTNG_UST_SYM_NAME_LEN - 1;
-	}
-	hash = jhash(name, name_len, 0);
-	head = &callsite_table[hash & (CALLSITE_TABLE_SIZE - 1)];
-	e = zmalloc(sizeof(struct callsite_entry));
-	assert(e);
-	cds_hlist_add_head(&e->hlist, head);
-	e->tp = tp;
-}
-
-/*
- * Remove the callsite from the callsite hash table and from lib
- * callsite list. Must be called with tracepoint mutex held.
- */
-static void remove_callsite(struct callsite_entry *e)
-{
-	cds_hlist_del(&e->hlist);
-	cds_list_del(&e->node);
-	free(e);
-}
-
 /*
  * Sets the probe callback corresponding to one tracepoint.
  */
@@ -393,6 +360,59 @@ static void disable_tracepoint(struct tracepoint *elem)
 	rcu_assign_pointer(elem->probes, NULL);
 }
 
+/*
+ * Add the callsite to the callsite hash table. Must be called with
+ * tracepoint mutex held.
+ */
+static void add_callsite(struct tracepoint_lib * lib, struct tracepoint *tp)
+{
+	struct cds_hlist_head *head;
+	struct callsite_entry *e;
+	const char *name = tp->name;
+	size_t name_len = strlen(name);
+	uint32_t hash;
+	struct tracepoint_entry *tp_entry;
+
+	if (name_len > LTTNG_UST_SYM_NAME_LEN - 1) {
+		WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1);
+		name_len = LTTNG_UST_SYM_NAME_LEN - 1;
+	}
+	hash = jhash(name, name_len, 0);
+	head = &callsite_table[hash & (CALLSITE_TABLE_SIZE - 1)];
+	e = zmalloc(sizeof(struct callsite_entry));
+	if (!e) {
+		PERROR("Unable to add callsite for tracepoint \"%s\"", name);
+		return;
+	}
+	cds_hlist_add_head(&e->hlist, head);
+	e->tp = tp;
+	cds_list_add(&e->node, &lib->callsites);
+
+	tp_entry = get_tracepoint(name);
+	if (!tp_entry)
+		return;
+	tp_entry->callsite_refcount++;
+}
+
+/*
+ * Remove the callsite from the callsite hash table and from lib
+ * callsite list. Must be called with tracepoint mutex held.
+ */
+static void remove_callsite(struct callsite_entry *e)
+{
+	struct tracepoint_entry *tp_entry;
+
+	tp_entry = get_tracepoint(e->tp->name);
+	if (tp_entry) {
+		tp_entry->callsite_refcount--;
+		if (tp_entry->callsite_refcount == 0)
+			disable_tracepoint(e->tp);
+	}
+	cds_hlist_del(&e->hlist);
+	cds_list_del(&e->node);
+	free(e);
+}
+
 /*
  * Enable/disable all callsites based on the state of a specific
  * tracepoint entry.
@@ -480,7 +500,7 @@ static void lib_register_callsites(struct tracepoint_lib *lib)
 		if (!(*iter)->name) {
 			continue;
 		}
-		add_callsite(*iter);
+		add_callsite(lib, *iter);
 	}
 }
 
@@ -704,24 +724,6 @@ static void new_tracepoints(struct tracepoint * const *start, struct tracepoint
 	}
 }
 
-static
-void lib_disable_tracepoints(struct tracepoint_lib *lib)
-{
-	struct tracepoint * const *begin;
-	struct tracepoint * const *end;
-	struct tracepoint * const *iter;
-
-	begin = lib->tracepoints_start;
-	end = lib->tracepoints_start + lib->tracepoints_count;
-
-	for (iter = begin; iter < end; iter++) {
-		if (!*iter)
-			continue;	/* skip dummy */
-		disable_tracepoint(*iter);
-	}
-
-}
-
 int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
 			    int tracepoints_count)
 {
@@ -730,7 +732,10 @@ int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
 	init_tracepoint();
 
 	pl = (struct tracepoint_lib *) zmalloc(sizeof(struct tracepoint_lib));
-
+	if (!pl) {
+		PERROR("Unable to register tracepoint lib");
+		return -1;
+	}
 	pl->tracepoints_start = tracepoints_start;
 	pl->tracepoints_count = tracepoints_count;
 	CDS_INIT_LIST_HEAD(&pl->callsites);
@@ -779,13 +784,11 @@ int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start)
 
 		cds_list_del(&lib->list);
 		/*
-		 * Force tracepoint disarm for all tracepoints of this lib.
-		 * This takes care of destructor of library that would leave a
-		 * LD_PRELOAD wrapper override function enabled for tracing, but
-		 * the session teardown would not be able to reach the
-		 * tracepoint anymore to disable it.
+		 * Unregistering a callsite also decreases the
+		 * callsite reference count of the corresponding
+		 * tracepoint, and disables the tracepoint if
+		 * the reference count drops to zero.
 		 */
-		lib_disable_tracepoints(lib);
 		lib_unregister_callsites(lib);
 		DBG("just unregistered a tracepoints section from %p",
 			lib->tracepoints_start);