X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-context-vtid.c;h=0a29021d4b104b3f4cb94deea5d72069dddc7145;hb=b4051ad8c170901d5297e1b3005b24e63cb0ab1e;hp=4b1da4f8e9b78541473f3e838352e04ac4461679;hpb=8c90a710949a214d87084ff67fc85f284bc93ef2;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-context-vtid.c b/liblttng-ust/lttng-context-vtid.c
index 4b1da4f8..0a29021d 100644
--- a/liblttng-ust/lttng-context-vtid.c
+++ b/liblttng-ust/lttng-context-vtid.c
@@ -20,6 +20,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#define _LGPL_SOURCE
+#include <stddef.h>
 #include <sys/types.h>
 #include <unistd.h>
 #include <lttng/ust-events.h>
@@ -42,11 +44,11 @@ static DEFINE_URCU_TLS(pid_t, cached_vtid);
  */
 void lttng_context_vtid_reset(void)
 {
-	URCU_TLS(cached_vtid) = 0;
+	CMM_STORE_SHARED(URCU_TLS(cached_vtid), 0);
 }
 
 static
-size_t vtid_get_size(size_t offset)
+size_t vtid_get_size(struct lttng_ctx_field *field, size_t offset)
 {
 	size_t size = 0;
 
@@ -55,16 +57,35 @@ size_t vtid_get_size(size_t offset)
 	return size;
 }
 
+static inline
+pid_t wrapper_getvtid(void)
+{
+	pid_t vtid;
+
+	vtid = CMM_LOAD_SHARED(URCU_TLS(cached_vtid));
+	if (caa_unlikely(!vtid)) {
+		vtid = lttng_gettid();
+		CMM_STORE_SHARED(URCU_TLS(cached_vtid), vtid);
+	}
+	return vtid;
+}
+
 static
 void vtid_record(struct lttng_ctx_field *field,
 		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
 		 struct lttng_channel *chan)
 {
-	if (caa_unlikely(!URCU_TLS(cached_vtid)))
-		URCU_TLS(cached_vtid) = gettid();
-	lib_ring_buffer_align_ctx(ctx, lttng_alignof(URCU_TLS(cached_vtid)));
-	chan->ops->event_write(ctx, &URCU_TLS(cached_vtid),
-		sizeof(URCU_TLS(cached_vtid)));
+	pid_t vtid = wrapper_getvtid();
+
+	lib_ring_buffer_align_ctx(ctx, lttng_alignof(vtid));
+	chan->ops->event_write(ctx, &vtid, sizeof(vtid));
+}
+
+static
+void vtid_get_value(struct lttng_ctx_field *field,
+		struct lttng_ctx_value *value)
+{
+	value->u.s64 = wrapper_getvtid();
 }
 
 int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx)
@@ -88,6 +109,8 @@ int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx)
 	field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
 	field->get_size = vtid_get_size;
 	field->record = vtid_record;
+	field->get_value = vtid_get_value;
+	lttng_context_update(*ctx);
 	return 0;
 }