From c1ef86f0812ff62354175f4c7136930814b8f850 Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 27 Sep 2011 20:46:04 -0400
Subject: [PATCH] Add vpid context

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 include/ust/lttng-events.h  |  2 +
 include/ust/lttng-ust-abi.h |  3 +-
 libust/Makefile.am          |  1 +
 libust/lttng-context-vpid.c | 95 +++++++++++++++++++++++++++++++++++++
 libust/lttng-ust-abi.c      |  2 +
 5 files changed, 102 insertions(+), 1 deletion(-)
 create mode 100644 libust/lttng-context-vpid.c

diff --git a/include/ust/lttng-events.h b/include/ust/lttng-events.h
index 6bb4e8cc..0439ea7a 100644
--- a/include/ust/lttng-events.h
+++ b/include/ust/lttng-events.h
@@ -321,7 +321,9 @@ void lttng_remove_context_field(struct lttng_ctx **ctx_p,
 				struct lttng_ctx_field *field);
 void lttng_destroy_context(struct lttng_ctx *ctx);
 int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx);
+int lttng_add_vpid_to_ctx(struct lttng_ctx **ctx);
 int lttng_add_pthread_id_to_ctx(struct lttng_ctx **ctx);
 void lttng_context_vtid_reset(void);
+void lttng_context_vpid_reset(void);
 
 #endif /* _UST_LTTNG_EVENTS_H */
diff --git a/include/ust/lttng-ust-abi.h b/include/ust/lttng-ust-abi.h
index 71465791..c967fb11 100644
--- a/include/ust/lttng-ust-abi.h
+++ b/include/ust/lttng-ust-abi.h
@@ -67,7 +67,8 @@ struct lttng_ust_event {
 
 enum lttng_ust_context_type {
 	LTTNG_UST_CONTEXT_VTID			= 0,
-	LTTNG_UST_CONTEXT_PTHREAD_ID		= 1,
+	LTTNG_UST_CONTEXT_VPID			= 1,
+	LTTNG_UST_CONTEXT_PTHREAD_ID		= 2,
 };
 
 struct lttng_ust_context {
diff --git a/libust/Makefile.am b/libust/Makefile.am
index 9857dd2d..cb00e179 100644
--- a/libust/Makefile.am
+++ b/libust/Makefile.am
@@ -20,6 +20,7 @@ libust_la_SOURCES = \
 	probes/lttng-probe-ust.c \
 	probes/lttng-probe-ust.h \
 	lttng-context-vtid.c \
+	lttng-context-vpid.c \
 	lttng-context-pthread-id.c \
 	ltt-context.c
 
diff --git a/libust/lttng-context-vpid.c b/libust/lttng-context-vpid.c
new file mode 100644
index 00000000..71395c95
--- /dev/null
+++ b/libust/lttng-context-vpid.c
@@ -0,0 +1,95 @@
+/*
+ * (C) Copyright	2009-2011 -
+ * 		Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * LTTng UST vpid context.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <ust/lttng-events.h>
+#include <ust/lttng-tracer.h>
+#include <ust/ringbuffer-config.h>
+
+#ifdef __linux__
+static inline
+pid_t wrapper_getpid(void)
+{
+	return getpid();
+}
+
+void lttng_context_vpid_reset(void)
+{
+}
+#else
+/*
+ * We cache the result to ensure we don't trigger a system call for
+ * each event.
+ */
+static pid_t cached_vpid;
+
+static inline
+pid_t wrapper_getpid(void)
+{
+	if (unlikely(!cached_vpid))
+		cached_vpid = getpid();
+	return cached_vpid;
+}
+
+/*
+ * Upon fork or clone, the PID assigned to our thread is not the same as
+ * we kept in cache.
+ */
+void lttng_context_vpid_reset(void)
+{
+	cached_vpid = 0;
+}
+#endif
+
+static
+size_t vpid_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 vpid_record(struct lttng_ctx_field *field,
+		 struct lib_ring_buffer_ctx *ctx,
+		 struct ltt_channel *chan)
+{
+	pid_t pid;
+
+	pid = wrapper_getpid();
+	lib_ring_buffer_align_ctx(ctx, lttng_alignof(pid));
+	chan->ops->event_write(ctx, &pid, sizeof(pid));
+}
+
+int lttng_add_vpid_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, "vpid")) {
+		lttng_remove_context_field(ctx, field);
+		return -EEXIST;
+	}
+	field->event_field.name = "vpid";
+	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 = vpid_get_size;
+	field->record = vpid_record;
+	return 0;
+}
diff --git a/libust/lttng-ust-abi.c b/libust/lttng-ust-abi.c
index 35c93c91..e125ac6d 100644
--- a/libust/lttng-ust-abi.c
+++ b/libust/lttng-ust-abi.c
@@ -276,6 +276,8 @@ long lttng_abi_add_context(int objd,
 		return lttng_add_pthread_id_to_ctx(ctx);
 	case LTTNG_UST_CONTEXT_VTID:
 		return lttng_add_vtid_to_ctx(ctx);
+	case LTTNG_UST_CONTEXT_VPID:
+		return lttng_add_vpid_to_ctx(ctx);
 	default:
 		return -EINVAL;
 	}
-- 
2.34.1