- sample support for LTTng userspace tracing

Makefile.config

 OPTIM?=1
+TRACING?=0
 DYNSTACK?=0
 OLDURING?=0
 
@@ -6,10 +7,26 @@ CFGFLAGS=-pthread -fPIC -Wall -Wextra
 DBGFLAGS=-ggdb # -fsanitize=address
 LANGFLAGS=-std=c++11
 
+CFLAGS=$(CFGFLAGS) $(DBGFLAGS) $(OPTFLAGS) $(STACKFLAGS) $(TLSFLAGS)
+CXXFLAGS=$(CFLAGS) $(LANGFLAGS)
+
 ifeq ($(OPTIM),1)
 OPTFLAGS=-O3 -fno-omit-frame-pointer
 endif
 
+ifeq ($(TRACING),1)
+LTTNG:=$(shell lttng-gen-tp --help 2>/dev/null)
+ifdef LTTNG
+CFLAGS+=-DTRACING
+else
+TRACING=0
+endif
+endif
+
+ifeq ($(OLDURING),1)
+CFLAGS+=-DOLDURING
+endif
+
 ifeq ($(DYNSTACK),1)
 STACKFLAGS=-fsplit-stack -DSPLIT_STACK
 else
@@ -24,10 +41,3 @@ endif
 ifeq ($(CC),clang)
 CXX=clang++
 endif
-
-CFLAGS=$(CFGFLAGS) $(DBGFLAGS) $(OPTFLAGS) $(STACKFLAGS) $(TLSFLAGS)
-CXXFLAGS=$(CFLAGS) $(LANGFLAGS)
-
-ifeq ($(OLDURING),1)
-CFLAGS+=-DOLDURING
-endif

README.md

@@ -36,6 +36,7 @@ In addition, the following students (in alphabetical order) have helped with var
 - Vrajang Parikh (gdb names & watchpoints)
 - Wen Shi (gdb extension)
 - Kai Sun (ARM64, mutex locks)
+- JinYang (Luke) Tao (LTTng)
 - Shuangyi Tong (event scopes)
 - Gan Wang (API/Apache)
 - Xinyi Zhou (worker/core affinity)

apps/Makefile

@@ -19,6 +19,10 @@ LIBS+=-L/usr/local/lib -Wl,-rpath=/usr/local/lib -luring
 endif
 endif
 
+ifeq ($(TRACING),1)
+LIBS+=-llttng-ust -ldl
+endif
+
 ifeq ($(shell uname),FreeBSD)
 LIBS+=-lpthread -lexecinfo # needed for backtrace_symbols()
 endif

src/Makefile

@@ -8,6 +8,11 @@ COBJECTS=$(subst .c,.o,$(notdir $(CSOURCES)))
 ASOURCES=$(wildcard $(addsuffix /*.S,$(SOURCEDIRS)))
 AOBJECTS=$(subst .S,.o,$(notdir $(ASOURCES)))
 
+ifeq ($(TRACING),1)
+TSOURCES=$(subst .tp,.c,$(wildcard tracing/*.tp))
+TOBJECTS=$(subst .tp,.o,$(wildcard tracing/*.tp))
+endif
+
 DEPENDS=$(subst .cc,.d,$(notdir $(SOURCES))) $(subst .c,.d,$(notdir $(CSOURCES))) $(subst .S,.d,$(notdir $(ASOURCES)))
 DEPENDS+=$(subst .c,.d,$(notdir $(CSOURCES)))
 
@@ -35,18 +40,18 @@ else
 	@for f in $^; do diff -y -W 80 --suppress-common-lines $$f.default $$f; done; true
 endif
 
-$(LIBA): $(OBJECTS) $(COBJECTS) $(AOBJECTS)
+$(LIBA): $(OBJECTS) $(COBJECTS) $(AOBJECTS) $(TOBJECTS)
 	$(AR) cr $@ $^
 	ranlib $@
 
-$(LIBSO): $(OBJECTS) $(COBJECTS) $(AOBJECTS)
+$(LIBSO): $(OBJECTS) $(COBJECTS) $(AOBJECTS) $(TOBJECTS)
 	$(CXX) -shared -pthread $^ -o $@
 
 $(GENHEADERS): %: %.default
 	@cp $< $@
 
 # also creates dependencies
-$(OBJECTS): %.o: %.cc $(GENHEADERS)
+$(OBJECTS): %.o: %.cc $(GENHEADERS) $(TSOURCES)
 	$(CXX) $(CXXFLAGS) -MMD -c $< -o $@
 
 $(COBJECTS): %.o: %.c
@@ -55,13 +60,16 @@ $(COBJECTS): %.o: %.c
 $(AOBJECTS): %.o: %.S
 	$(CC) $(CFLAGS) -MMD -c $< -o $@
 
+$(TSOURCES): %.c: %.tp
+	lttng-gen-tp $< -o $@ -o $(subst .c,.h,$@)
+
 $(OBJECTS) errnoname/errnoname.c: errnoname/errnoname.h
 
 errnoname/errnoname.h:
 	git submodule update --init errnoname
 
 clean:
-	rm -f $(LIBA) $(LIBSO) $(OBJECTS) $(COBJECTS) $(AOBJECTS) $(DEPENDS)
+	rm -f $(LIBA) $(LIBSO) $(OBJECTS) $(COBJECTS) $(AOBJECTS) $(DEPENDS) tracing/*.?
 
 vclean: clean
 	rm -f $(GENHEADERS)

src/runtime/BlockingSync.h

@@ -28,6 +28,12 @@
 
 #include <map>
 
+#if TRACING
+#include "tracing/BlockingSyncTrace.h"
+#else
+#define lttng_ust_tracepoint(provider, name, ...)
+#endif
+
 /****************************** Basics ******************************/
 
 struct Suspender { // funnel suspend calls through this class for access control
@@ -165,7 +171,9 @@ class BlockingQueue {
     queue.push_back(node);
     lock.release();
     // block, potentially with timeout
+    lttng_ust_tracepoint(BlockingSyncTrace, blocking, (uintptr_t)Context::CurrFred(), (uintptr_t)this, "block");
     ptr_t winner = blockHelper(*cf, args...);
+    lttng_ust_tracepoint(BlockingSyncTrace, blocking, (uintptr_t)Context::CurrFred(), (uintptr_t)this, "unblock");
     if (winner == &queue) return true; // blocking completed;
     // clean up
     ScopedLock<Lock> sl(lock);
@@ -177,7 +185,9 @@ class BlockingQueue {
   BlockingQueue& operator=(const BlockingQueue&) = delete; // no assignment
 
 public:
-  BlockingQueue() = default;
+  BlockingQueue() {
+    lttng_ust_tracepoint(BlockingSyncTrace, blocking, (uintptr_t)Context::CurrFred(), (uintptr_t)this, "init");
+  }
   ~BlockingQueue() { RASSERT0(empty()); }
   bool empty() const { return queue.empty(); }
 
@@ -207,12 +217,14 @@ public:
 
   template<bool Enqueue>
   Fred* unblock() {                     // Note that caller must hold lock
+    lttng_ust_tracepoint(BlockingSyncTrace, blocking, (uintptr_t)Context::CurrFred(), (uintptr_t)this, "resume");
     for (Node* node = queue.front(); node != queue.edge(); node = IntrusiveList<Node>::next(*node)) {
       Fred* f = &node->fred;
       if (f->raceResume(&queue)) {
         IntrusiveList<Node>::remove(*node);
         DBG::outl(DBG::Level::Blocking, "Fred ", FmtHex(f), " resume from ", FmtHex(&queue));
         if (Enqueue) f->resume();
+        lttng_ust_tracepoint(BlockingSyncTrace, blocking, (uintptr_t)f, (uintptr_t)this, "resumed");
         return f;
       }
     }

src/tracing/BlockingSyncTrace.tp

+LTTNG_UST_TRACEPOINT_EVENT(
+	BlockingSyncTrace, blocking,
+	LTTNG_UST_TP_ARGS(uintptr_t, cfibreptr, uintptr_t, queueptr, const char *, eventstr),
+	LTTNG_UST_TP_FIELDS(
+		lttng_ust_field_integer(uintptr_t, fibre_address, cfibreptr)
+		lttng_ust_field_integer(uintptr_t, queue_address, queueptr)
+		lttng_ust_field_string(event_string, eventstr)
+	)
+)