From: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Date: Fri, 8 Jul 2022 21:19:32 +0000 (-0400)
Subject: Fix: ust metadata: resample clock on regenerate metadata
X-Git-Url: https://git.liburcu.org/?p=lttng-tools.git;a=commitdiff_plain;h=042670db60ac672661e1bbc8de4da1d8590e20b4

Fix: ust metadata: resample clock on regenerate metadata

Observed issue
==============
The system test jobs complain that the clock regeneration is broken
since the move to the tsdl visitor approach for metadata generation.

 # Test UST local with metadata regeneration
 # destructive//../../src/bin/lttng/lttng create regen -o /tmp/tmp.metadata_regen_after_data_change.Vzb0vL
 ok 23 - Create session regen in -o /tmp/tmp.metadata_regen_after_data_change.Vzb0vL
 # destructive//../../src/bin/lttng/lttng enable-event tp:tptest -s regen -u
 ok 24 - Enable ust event tp:tptest for session regen
 # destructive//../../src/bin/lttng/lttng start regen
 ok 25 - Start tracing for session regen
 # destructive//../../src/bin/lttng/lttng stop regen
 ok 26 - Stop lttng tracing for session regen
 ok 27 - Validate trace at date 1970-02-02
 # destructive//../../src/bin/lttng/lttng start regen
 ok 28 - Start tracing for session regen
 # destructive//../../src/bin/lttng/lttng regenerate metadata -s regen
 ok 29 - Metadata regenerate regen
 # destructive//../../src/bin/lttng/lttng stop regen
 ok 30 - Stop lttng tracing for session regen
 # destructive//../../src/bin/lttng/lttng destroy regen
 ok 31 - Destroy session regen
 not ok 32 - The trace is not at the expected date
 #   Failed test 'The trace is not at the expected date'
 #   in destructive//../utils/tap/tap.sh:fail() at line 159.

Cause
=====

Previously the clock was sampled on each call to `ust_metadata_session_statedump`
, currently the clock is only sampled on creation of the
`lttng::sessiond::ust::registry_session::registry_session` object.

Solution
========

On `lsu::registry_session::regenerate_metadata`, sample the clock and
replace the registry_session _clock object.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Change-Id: I6f671e4c01f71e1574824236cef03915a9c79b36
---

diff --git a/src/bin/lttng-sessiond/clock-class.hpp b/src/bin/lttng-sessiond/clock-class.hpp
index 3a4755d07..58adc8eac 100644
--- a/src/bin/lttng-sessiond/clock-class.hpp
+++ b/src/bin/lttng-sessiond/clock-class.hpp
@@ -30,6 +30,7 @@ class clock_class {
 public:
 	using cycles_t = uint64_t;
 	using scycles_t = int64_t;
+	using cuptr = std::unique_ptr<const clock_class>;
 
 	const std::string name;
 	const std::string description;
diff --git a/src/bin/lttng-sessiond/ust-registry-session.cpp b/src/bin/lttng-sessiond/ust-registry-session.cpp
index 5bb8e6094..eced786e0 100644
--- a/src/bin/lttng-sessiond/ust-registry-session.cpp
+++ b/src/bin/lttng-sessiond/ust-registry-session.cpp
@@ -246,6 +246,7 @@ lsu::registry_session::registry_session(const struct lst::abi& in_abi,
 	_gid{egid},
 	_app_tracer_version{.major = major, .minor = minor},
 	_tracing_id{tracing_id},
+	_clock{lttng::make_unique<lsu::clock_class>()},
 	_metadata_generating_visitor{lttng::make_unique<ls::tsdl::trace_class_visitor>(abi,
 			[this](const std::string& fragment) {
 				_append_metadata_fragment(fragment);
@@ -487,7 +488,7 @@ void lsu::registry_session::_visit_environment(
 void lsu::registry_session::_accept_on_clock_classes(lst::trace_class_visitor& visitor) const
 {
 	ASSERT_LOCKED(_lock);
-	_clock.accept(visitor);
+	_clock->accept(visitor);
 }
 
 void lsu::registry_session::_accept_on_stream_classes(lst::trace_class_visitor& visitor) const
@@ -613,6 +614,9 @@ void lsu::registry_session::regenerate_metadata()
 {
 	lttng::pthread::lock_guard registry_lock(_lock);
 
+	/* Resample the clock */
+	_clock = lttng::make_unique<lsu::clock_class>();
+
 	_metadata_version++;
 	_reset_metadata();
 	_generate_metadata();
diff --git a/src/bin/lttng-sessiond/ust-registry-session.hpp b/src/bin/lttng-sessiond/ust-registry-session.hpp
index cce7c5c1b..316703769 100644
--- a/src/bin/lttng-sessiond/ust-registry-session.hpp
+++ b/src/bin/lttng-sessiond/ust-registry-session.hpp
@@ -191,7 +191,7 @@ private:
 	/* The id of the parent session. */
 	const ltt_session::id_t _tracing_id;
 
-	lttng::sessiond::ust::clock_class _clock;
+	lttng::sessiond::ust::clock_class::cuptr _clock;
 	const lttng::sessiond::trace::trace_class_visitor::cuptr _metadata_generating_visitor;
 };