Move all sources to 'src/'

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

diff --git a/src/liblttng-ust/lttng-context-vtid.c b/src/liblttng-ust/lttng-context-vtid.c
new file mode 100644 (file)
index 0000000..3530d26
--- /dev/null
+++ b/src/liblttng-ust/lttng-context-vtid.c
@@ -0,0 +1,115 @@
+/*
+ * SPDX-License-Identifier: LGPL-2.1-only
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * LTTng UST vtid context.
+ */
+
+#define _LGPL_SOURCE
+#include <limits.h>
+#include <stddef.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <lttng/ust-events.h>
+#include <lttng/ust-tracer.h>
+#include <lttng/ringbuffer-context.h>
+#include <ust-tid.h>
+#include <urcu/tls-compat.h>
+
+#include "context-internal.h"
+#include "lttng-tracer-core.h"
+
+/*
+ * We cache the result to ensure we don't trigger a system call for
+ * each event.
+ */
+static DEFINE_URCU_TLS(pid_t, cached_vtid);
+
+/*
+ * Upon fork or clone, the TID assigned to our thread is not the same as
+ * we kept in cache. Luckily, we are the only thread surviving in the
+ * child process, so we can simply clear our cached version.
+ */
+void lttng_context_vtid_reset(void)
+{
+       CMM_STORE_SHARED(URCU_TLS(cached_vtid), 0);
+}
+
+static
+size_t vtid_get_size(void *priv __attribute__((unused)),
+               size_t offset)
+{
+       size_t size = 0;
+
+       size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(pid_t));
+       size += sizeof(pid_t);
+       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(void *priv __attribute__((unused)),
+                struct lttng_ust_lib_ring_buffer_ctx *ctx,
+                struct lttng_ust_channel_buffer *chan)
+{
+       pid_t vtid = wrapper_getvtid();
+
+       chan->ops->event_write(ctx, &vtid, sizeof(vtid), lttng_ust_rb_alignof(vtid));
+}
+
+static
+void vtid_get_value(void *priv __attribute__((unused)),
+               struct lttng_ust_ctx_value *value)
+{
+       value->u.s64 = wrapper_getvtid();
+}
+
+static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field(
+       lttng_ust_static_event_field("vtid",
+               lttng_ust_static_type_integer(sizeof(pid_t) * CHAR_BIT,
+                               lttng_ust_rb_alignof(pid_t) * CHAR_BIT,
+                               lttng_ust_is_signed_type(pid_t),
+                               BYTE_ORDER, 10),
+               false, false),
+       vtid_get_size,
+       vtid_record,
+       vtid_get_value,
+       NULL, NULL);
+
+int lttng_add_vtid_to_ctx(struct lttng_ust_ctx **ctx)
+{
+       int ret;
+
+       if (lttng_find_context(*ctx, ctx_field->event_field->name)) {
+               ret = -EEXIST;
+               goto error_find_context;
+       }
+       ret = lttng_ust_context_append(ctx, ctx_field);
+       if (ret)
+               return ret;
+       return 0;
+
+error_find_context:
+       return ret;
+}
+
+/*
+ * Force a read (imply TLS fixup for dlopen) of TLS variables.
+ */
+void lttng_fixup_vtid_tls(void)
+{
+       asm volatile ("" : : "m" (URCU_TLS(cached_vtid)));
+}