Cleanup vtid/vpid context caches

[lttng-ust.git] / liblttng-ust / lttng-context-vtid.c

diff --git a/liblttng-ust/lttng-context-vtid.c b/liblttng-ust/lttng-context-vtid.c
index f28e470a38c91be3e88c7b1d1fcd42c591d73c67..5cefe9538486a38ffba957fe06b8601b907ff744 100644 (file)
--- a/liblttng-ust/lttng-context-vtid.c
+++ b/liblttng-ust/lttng-context-vtid.c
@@ -43,7 +43,7 @@ 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
@@ -56,25 +56,35 @@ size_t vtid_get_size(struct lttng_ctx_field *field, 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 = getpid();
+               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)
 {
-       if (caa_unlikely(!URCU_TLS(cached_vtid)))
-               URCU_TLS(cached_vtid) = gettid();
-       value->u.s64 = URCU_TLS(cached_vtid);
+       value->u.s64 = wrapper_getvtid();
 }
 
 int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx)