X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-context-vtid.c;fp=liblttng-ust%2Flttng-context-vtid.c;h=6f7e078d22d2910072748adfd0ee59b8c9a695b4;hb=69400ac4a4e6575f749c6326df7c2a2c8ac3bdc5;hp=0000000000000000000000000000000000000000;hpb=f3049ad9e7b72287888452b9ed542c0f36e6eefe;p=ust.git

diff --git a/liblttng-ust/lttng-context-vtid.c b/liblttng-ust/lttng-context-vtid.c
new file mode 100644
index 0000000..6f7e078
--- /dev/null
+++ b/liblttng-ust/lttng-context-vtid.c
@@ -0,0 +1,94 @@
+/*
+ * (C) Copyright	2009-2011 -
+ * 		Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * LTTng UST vtid context.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <lttng/ust-events.h>
+#include <lttng/ust-tracer.h>
+#include <lttng/ringbuffer-config.h>
+
+#ifdef __linux__
+#include <syscall.h>
+#endif
+
+#if defined(_syscall0)
+_syscall0(pid_t, gettid)
+#elif defined(__NR_gettid)
+static inline pid_t gettid(void)
+{
+	return syscall(__NR_gettid);
+}
+#else
+#warning "use pid as tid"
+static inline pid_t gettid(void)
+{
+	return getpid();
+}
+#endif
+
+/*
+ * We cache the result to ensure we don't trigger a system call for
+ * each event.
+ */
+static __thread 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)
+{
+	cached_vtid = 0;
+}
+
+static
+size_t vtid_get_size(size_t offset)
+{
+	size_t size = 0;
+
+	size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
+	size += sizeof(pid_t);
+	return size;
+}
+
+static
+void vtid_record(struct lttng_ctx_field *field,
+		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
+		 struct ltt_channel *chan)
+{
+	if (caa_unlikely(!cached_vtid))
+		cached_vtid = gettid();
+	lib_ring_buffer_align_ctx(ctx, lttng_alignof(cached_vtid));
+	chan->ops->event_write(ctx, &cached_vtid, sizeof(cached_vtid));
+}
+
+int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx)
+{
+	struct lttng_ctx_field *field;
+
+	field = lttng_append_context(ctx);
+	if (!field)
+		return -ENOMEM;
+	if (lttng_find_context(*ctx, "vtid")) {
+		lttng_remove_context_field(ctx, field);
+		return -EEXIST;
+	}
+	field->event_field.name = "vtid";
+	field->event_field.type.atype = atype_integer;
+	field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT;
+	field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
+	field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t);
+	field->event_field.type.u.basic.integer.reverse_byte_order = 0;
+	field->event_field.type.u.basic.integer.base = 10;
+	field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
+	field->get_size = vtid_get_size;
+	field->record = vtid_record;
+	return 0;
+}