Add tracing annotations to absl::BlockingCounter

PiperOrigin-RevId: 656010740
Change-Id: I99ef6f18502a0cb2c363c805ae5f9a9a42bd3b41

absl/base/internal/tracing.h

@@ -22,7 +22,7 @@ ABSL_NAMESPACE_BEGIN
 namespace base_internal {
 
 // Well known Abseil object types that have causality.
-enum class ObjectKind { kUnknown };
+enum class ObjectKind { kUnknown, kBlockingCounter };
 
 // `TraceWait` and `TraceContinue` record the start and end of a potentially
 // blocking wait operation on `object`. `object` typically represents a higher
@@ -47,14 +47,14 @@ void TraceObserved(const void* object, ObjectKind kind);
 // ---------------------------------------------------------------------------
 extern "C" {
 
-void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceWait)(const void* object,
-                                                   ObjectKind kind);
-void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceContinue)(const void* object,
-                                                       ObjectKind kind);
-void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceSignal)(const void* object,
+  void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceWait)(const void* object,
                                                      ObjectKind kind);
-void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceObserved)(const void* object,
+  void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceContinue)(const void* object,
+                                                         ObjectKind kind);
+  void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceSignal)(const void* object,
                                                        ObjectKind kind);
+  void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceObserved)(const void* object,
+                                                         ObjectKind kind);
 
 }  // extern "C"
 

absl/synchronization/BUILD.bazel

@@ -141,6 +141,7 @@ cc_library(
         "//absl/base:dynamic_annotations",
         "//absl/base:malloc_internal",
         "//absl/base:raw_logging_internal",
+        "//absl/base:tracing_internal",
         "//absl/debugging:stacktrace",
         "//absl/debugging:symbolize",
         "//absl/time",
@@ -177,6 +178,9 @@ cc_test(
     ],
     deps = [
         ":synchronization",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/base:tracing_internal",
         "//absl/time",
         "@com_google_googletest//:gtest",
         "@com_google_googletest//:gtest_main",

absl/synchronization/CMakeLists.txt

@@ -113,6 +113,7 @@ absl_cc_library(
     absl::stacktrace
     absl::symbolize
     absl::time
+    absl::tracing_internal
     Threads::Threads
   PUBLIC
 )
@@ -140,6 +141,7 @@ absl_cc_test(
   DEPS
     absl::synchronization
     absl::time
+    absl::tracing_internal
     GTest::gmock_main
 )
 

absl/synchronization/blocking_counter.cc

@@ -17,6 +17,7 @@
 #include <atomic>
 
 #include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/tracing.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -40,6 +41,7 @@ bool BlockingCounter::DecrementCount() {
   ABSL_RAW_CHECK(count >= 0,
                  "BlockingCounter::DecrementCount() called too many times");
   if (count == 0) {
+    base_internal::TraceSignal(this, TraceObjectKind());
     MutexLock l(&lock_);
     done_ = true;
     return true;
@@ -48,19 +50,23 @@ bool BlockingCounter::DecrementCount() {
 }
 
 void BlockingCounter::Wait() {
-  MutexLock l(&this->lock_);
+  base_internal::TraceWait(this, TraceObjectKind());
+  {
+    MutexLock l(&this->lock_);
 
-  // only one thread may call Wait(). To support more than one thread,
-  // implement a counter num_to_exit, like in the Barrier class.
-  ABSL_RAW_CHECK(num_waiting_ == 0, "multiple threads called Wait()");
-  num_waiting_++;
+    // only one thread may call Wait(). To support more than one thread,
+    // implement a counter num_to_exit, like in the Barrier class.
+    ABSL_RAW_CHECK(num_waiting_ == 0, "multiple threads called Wait()");
+    num_waiting_++;
 
-  this->lock_.Await(Condition(IsDone, &this->done_));
+    this->lock_.Await(Condition(IsDone, &this->done_));
 
-  // At this point, we know that all threads executing DecrementCount
-  // will not touch this object again.
-  // Therefore, the thread calling this method is free to delete the object
-  // after we return from this method.
+    // At this point, we know that all threads executing DecrementCount
+    // will not touch this object again.
+    // Therefore, the thread calling this method is free to delete the object
+    // after we return from this method.
+  }
+  base_internal::TraceContinue(this, TraceObjectKind());
 }
 
 ABSL_NAMESPACE_END

absl/synchronization/blocking_counter.h

@@ -22,6 +22,7 @@
 
 #include <atomic>
 
+#include "absl/base/internal/tracing.h"
 #include "absl/base/thread_annotations.h"
 #include "absl/synchronization/mutex.h"
 
@@ -89,6 +90,11 @@ class BlockingCounter {
   void Wait();
 
  private:
+  // Convenience helper to reduce verbosity at call sites.
+  static inline constexpr base_internal::ObjectKind TraceObjectKind() {
+    return base_internal::ObjectKind::kBlockingCounter;
+  }
+
   Mutex lock_;
   std::atomic<int> count_;
   int num_waiting_ ABSL_GUARDED_BY(lock_);

absl/synchronization/blocking_counter_test.cc

@@ -15,9 +15,13 @@
 #include "absl/synchronization/blocking_counter.h"
 
 #include <thread>  // NOLINT(build/c++11)
+#include <tuple>
 #include <vector>
 
 #include "gtest/gtest.h"
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/tracing.h"
 #include "absl/time/clock.h"
 #include "absl/time/time.h"
 
@@ -76,5 +80,67 @@ TEST(BlockingCounterTest, WaitNegativeInitialCount) {
 #endif
 
 }  // namespace
+
+#if ABSL_HAVE_ATTRIBUTE_WEAK
+
+namespace base_internal {
+
+namespace {
+
+using TraceRecord = std::tuple<const void*, ObjectKind>;
+
+thread_local TraceRecord tls_signal;
+thread_local TraceRecord tls_wait;
+thread_local TraceRecord tls_continue;
+
+}  // namespace
+
+// Strong extern "C" implementation.
+extern "C" {
+
+void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceWait)(const void* object,
+                                                   ObjectKind kind) {
+  tls_wait = {object, kind};
+}
+
+void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceContinue)(const void* object,
+                                                       ObjectKind kind) {
+  tls_continue = {object, kind};
+}
+
+void ABSL_INTERNAL_C_SYMBOL(AbslInternalTraceSignal)(const void* object,
+                                                     ObjectKind kind) {
+  tls_signal = {object, kind};
+}
+
+}  // extern "C"
+
+TEST(BlockingCounterTest, TracesSignal) {
+  BlockingCounter counter(2);
+
+  tls_signal = {};
+  counter.DecrementCount();
+  EXPECT_EQ(tls_signal, TraceRecord(nullptr, ObjectKind::kUnknown));
+
+  tls_signal = {};
+  counter.DecrementCount();
+  EXPECT_EQ(tls_signal, TraceRecord(&counter, ObjectKind::kBlockingCounter));
+}
+
+TEST(BlockingCounterTest, TracesWaitContinue) {
+  BlockingCounter counter(1);
+  counter.DecrementCount();
+
+  tls_wait = {};
+  tls_continue = {};
+  counter.Wait();
+  EXPECT_EQ(tls_wait, TraceRecord(&counter, ObjectKind::kBlockingCounter));
+  EXPECT_EQ(tls_continue, TraceRecord(&counter, ObjectKind::kBlockingCounter));
+}
+
+}  // namespace base_internal
+
+#endif  // ABSL_HAVE_ATTRIBUTE_WEAK
+
 ABSL_NAMESPACE_END
 }  // namespace absl