Cleanup vtid/vpid context caches

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
(cherry picked from commit 98357ffd0125c23387d42d4b706c56077392326d)

Change-Id: Ibeb53ecd773cdda701b90f09b465d82e88130e23

diff --git a/liblttng-ust/lttng-context-vpid.c b/liblttng-ust/lttng-context-vpid.c
index ab23011..c5646cb 100644 (file)
--- a/liblttng-ust/lttng-context-vpid.c
+++ b/liblttng-ust/lttng-context-vpid.c
@@ -33,11 +33,16 @@
 static pid_t cached_vpid;
 
 static inline
-pid_t wrapper_getpid(void)
+pid_t wrapper_getvpid(void)
 {
-       if (caa_unlikely(!cached_vpid))
-               cached_vpid = getpid();
-       return cached_vpid;
+       pid_t vpid;
+
+       vpid = CMM_LOAD_SHARED(cached_vpid);
+       if (caa_unlikely(!vpid)) {
+               vpid = getpid();
+               CMM_STORE_SHARED(cached_vpid, vpid);
+       }
+       return vpid;
 }
 
 /*
@@ -46,7 +51,7 @@ pid_t wrapper_getpid(void)
  */
 void lttng_context_vpid_reset(void)
 {
-       cached_vpid = 0;
+       CMM_STORE_SHARED(cached_vpid, 0);
 }
 
 static
@@ -64,21 +69,17 @@ void vpid_record(struct lttng_ctx_field *field,
                 struct lttng_ust_lib_ring_buffer_ctx *ctx,
                 struct lttng_channel *chan)
 {
-       pid_t pid;
+       pid_t vpid = wrapper_getvpid();
 
-       pid = wrapper_getpid();
-       lib_ring_buffer_align_ctx(ctx, lttng_alignof(pid));
-       chan->ops->event_write(ctx, &pid, sizeof(pid));
+       lib_ring_buffer_align_ctx(ctx, lttng_alignof(vpid));
+       chan->ops->event_write(ctx, &vpid, sizeof(vpid));
 }
 
 static
 void vpid_get_value(struct lttng_ctx_field *field,
                struct lttng_ctx_value *value)
 {
-       pid_t pid;
-
-       pid = wrapper_getpid();
-       value->u.s64 = pid;
+       value->u.s64 = wrapper_getvpid();
 }
 
 int lttng_add_vpid_to_ctx(struct lttng_ctx **ctx)

diff --git a/liblttng-ust/lttng-context-vtid.c b/liblttng-ust/lttng-context-vtid.c
index d1c73d8..a213b26 100644 (file)
--- a/liblttng-ust/lttng-context-vtid.c
+++ b/liblttng-ust/lttng-context-vtid.c
@@ -42,7 +42,7 @@ 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
@@ -55,25 +55,35 @@ 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)