[Threading][TSan] Move ThreadSanitizer.cpp into the main runtime.

On Darwin, `RTLD_NEXT` doesn't do what we need it to here, with the
result that if `libswiftCore`'s TSan initializer gets found first,
then `libswift_Concurrency` won't have its initializer called at all,
in spite of us using `RTLD_NEXT` to find the next definition.

Fix this by centralising the initializer in `libswiftCore` instead.

rdar://110665213

Author: al45tair

include/swift/Threading/ThreadSanitizer.h

@@ -20,6 +20,8 @@
 #ifndef SWIFT_THREADING_THREAD_SANITIZER_H
 #define SWIFT_THREADING_THREAD_SANITIZER_H
 
+#include "swift/shims/Visibility.h"
+
 namespace swift {
 
 #if defined(_WIN32) || defined(__wasi__) || !__has_include(<dlfcn.h>)
@@ -34,17 +36,17 @@ template <typename T> T *release(T *ptr) { return ptr; }
 
 namespace threading_impl {
 
-extern bool tsan_enabled;
-extern void (*tsan_acquire)(const void *ptr);
-extern void (*tsan_release)(const void *ptr);
+SWIFT_RUNTIME_EXPORT bool _swift_tsan_enabled;
+SWIFT_RUNTIME_EXPORT void (*_swift_tsan_acquire)(const void *ptr);
+SWIFT_RUNTIME_EXPORT void (*_swift_tsan_release)(const void *ptr);
 
 } // namespace threading_impl
 
 namespace tsan {
 
 /// Returns true if TSan is enabled
 inline bool enabled() {
-  return threading_impl::tsan_enabled;
+  return threading_impl::_swift_tsan_enabled;
 }
 
 /// Indicate to TSan that an acquiring load has occurred on the current
@@ -54,8 +56,8 @@ inline bool enabled() {
 /// `acquire()`.
 template <typename T>
 T *acquire(T *ptr) {
-  if (threading_impl::tsan_acquire) {
-    threading_impl::tsan_acquire(ptr);
+  if (threading_impl::_swift_tsan_acquire) {
+    threading_impl::_swift_tsan_acquire(ptr);
   }
   return ptr;
 }
@@ -66,8 +68,8 @@ T *acquire(T *ptr) {
 /// see all writes that happened before the `release()`.
 template <typename T>
 T *release(T *ptr) {
-  if (threading_impl::tsan_release) {
-    threading_impl::tsan_release(ptr);
+  if (threading_impl::_swift_tsan_release) {
+    threading_impl::_swift_tsan_release(ptr);
   }
   return ptr;
 }

lib/Threading/CMakeLists.txt

@@ -10,5 +10,4 @@ add_swift_host_library(swiftThreading STATIC
   Linux.cpp
   Pthreads.cpp
   Win32.cpp
-  Errors.cpp
-  ThreadSanitizer.cpp)
+  Errors.cpp)

stdlib/public/Threading/CMakeLists.txt

@@ -9,5 +9,4 @@ add_swift_target_library(swiftThreading OBJECT_LIBRARY
   "${SWIFT_SOURCE_DIR}/lib/Threading/Linux.cpp"
   "${SWIFT_SOURCE_DIR}/lib/Threading/Pthreads.cpp"
   "${SWIFT_SOURCE_DIR}/lib/Threading/Win32.cpp"
-  "${SWIFT_SOURCE_DIR}/lib/Threading/ThreadSanitizer.cpp"
   INSTALL_IN_COMPONENT never_install)

stdlib/public/runtime/CMakeLists.txt

@@ -76,6 +76,7 @@ set(swift_runtime_sources
     SwiftDtoa.cpp
     SwiftTLSContext.cpp
     ThreadingError.cpp
+    ThreadSanitizer.cpp
     Tracing.cpp
     AccessibleFunction.cpp
     Win32.cpp)

lib/Threading/ThreadSanitizer.cpp renamed to stdlib/public/runtime/ThreadSanitizer.cpp

@@ -20,28 +20,35 @@
 #include "swift/Threading/ThreadSanitizer.h"
 #include "swift/shims/Visibility.h"
 
+#include <cstdio>
+
 namespace swift {
 namespace threading_impl {
 
-bool tsan_enabled = false;
-void (*tsan_acquire)(const void *) = nullptr;
-void (*tsan_release)(const void *) = nullptr;
+SWIFT_RUNTIME_EXPORT bool _swift_tsan_enabled = false;
+SWIFT_RUNTIME_EXPORT void (*_swift_tsan_acquire)(const void *) = nullptr;
+SWIFT_RUNTIME_EXPORT void (*_swift_tsan_release)(const void *) = nullptr;
 
 #if __has_include(<dlfcn.h>)
 #include <dlfcn.h>
 
 // The TSan library code will call this function when it starts up
-extern "C" SWIFT_ATTRIBUTE_FOR_EXPORTS
+SWIFT_RUNTIME_EXPORT
 void __tsan_on_initialize() {
-  tsan_enabled = true;
-  tsan_acquire = (void (*)(const void *))dlsym(RTLD_DEFAULT, "__tsan_acquire");
-  tsan_release = (void (*)(const void *))dlsym(RTLD_DEFAULT, "__tsan_release");
+  _swift_tsan_enabled = true;
+  _swift_tsan_acquire = (void (*)(const void *))dlsym(RTLD_DEFAULT,
+                                                      "__tsan_acquire");
+  _swift_tsan_release = (void (*)(const void *))dlsym(RTLD_DEFAULT,
+                                                      "__tsan_release");
 
-  // Always call through to the next image
+  // Always call through to the next image; this won't work on macOS, but it's
+  // important on Linux to allow others to hook into the thread sanitizer if
+  // they wish.
   void (*next_init)(void);
   next_init = (void (*)(void))dlsym(RTLD_NEXT, "__tsan_on_initialize");
-  if (next_init)
+  if (next_init) {
     next_init();
+  }
 }
 #endif