Merge pull request #38163 from mikeash/concurrency-constant-pthread-keys-5.5

[5.5][Concurrency] Use pthread_specific for thread-local storage on Darwin.

Author: DougGregor

include/swift/Runtime/ThreadLocal.h

@@ -18,9 +18,15 @@
 #ifndef SWIFT_RUNTIME_THREADLOCAL_H
 #define SWIFT_RUNTIME_THREADLOCAL_H
 
+#include <type_traits>
+#include "ThreadLocalStorage.h"
+
 /// SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL - Does the current configuration
 /// allow the use of SWIFT_RUNTIME_ATTRIBUTE_THREAD_LOCAL?
-#if defined(SWIFT_STDLIB_SINGLE_THREADED_RUNTIME)
+#if defined(__APPLE__)
+// The pthread TLS APIs work better than C++ TLS on Apple platforms.
+#define SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL 0
+#elif defined(SWIFT_STDLIB_SINGLE_THREADED_RUNTIME)
 // We define SWIFT_RUNTIME_ATTRIBUTE_THREAD_LOCAL to nothing in this
 // configuration and just use a global variable, so this is okay.
 #define SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL 1
@@ -57,6 +63,17 @@
 #endif
 
 namespace swift {
+// Validate a type stored in thread-local storage, using static asserts. Such
+// types must fit in a pointer and be trivially copyable/destructible.
+#define VALIDATE_THREAD_LOCAL_TYPE(T)                                          \
+  static_assert(sizeof(T) <= sizeof(void *),                                   \
+                "cannot store more than a pointer");                           \
+  static_assert(std::is_trivially_copyable<T>::value,                          \
+                "ThreadLocal values must be trivially copyable");              \
+  static_assert(std::is_trivially_destructible<T>::value,                      \
+                "ThreadLocal cleanup is not supported, stored types must be "  \
+                "trivially destructible");
+
 // A wrapper class for thread-local storage.
 //
 // - On platforms that report SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL
@@ -72,50 +89,70 @@ namespace swift {
 // - On platforms that don't report SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL,
 //   we have to simulate thread-local storage.  Fortunately, all of
 //   these platforms (at least for now) support pthread_getspecific.
+#if SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL
 template <class T>
 class ThreadLocal {
-  static_assert(sizeof(T) <= sizeof(void*), "cannot store more than a pointer");
+  VALIDATE_THREAD_LOCAL_TYPE(T)
 
-#if SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL
   T value;
+
+public:
+  constexpr ThreadLocal() {}
+
+  T get() { return value; }
+
+  void set(T newValue) { value = newValue; }
+};
 #else
+// A wrapper around a pthread_key_t that is lazily initialized using
+// dispatch_once.
+class ThreadLocalKey {
   // We rely on the zero-initialization of objects with static storage
   // duration.
   dispatch_once_t once;
   pthread_key_t key;
 
+public:
   pthread_key_t getKey() {
-    dispatch_once_f(&once, this, [](void *ctx) {
-      pthread_key_create(&reinterpret_cast<ThreadLocal*>(ctx)->key, nullptr);
+    dispatch_once_f(&once, &key, [](void *ctx) {
+      pthread_key_create(reinterpret_cast<pthread_key_t *>(ctx), nullptr);
     });
     return key;
   }
-#endif
+};
+
+// A type representing a constant pthread_key_t, for use on platforms that
+// provide reserved keys.
+template <pthread_key_t constantKey>
+class ConstantThreadLocalKey {
+public:
+  pthread_key_t getKey() { return constantKey; }
+};
+
+template <class T, class Key>
+class ThreadLocal {
+  VALIDATE_THREAD_LOCAL_TYPE(T)
+
+  Key key;
 
 public:
   constexpr ThreadLocal() {}
 
   T get() {
-#if SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL
-    return value;
-#else
-    void *storedValue = pthread_getspecific(getKey());
+    void *storedValue = SWIFT_THREAD_GETSPECIFIC(key.getKey());
     T value;
     memcpy(&value, &storedValue, sizeof(T));
     return value;
-#endif
   }
 
   void set(T newValue) {
-#if SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL
-    value = newValue;
-#else
     void *storedValue;
     memcpy(&storedValue, &newValue, sizeof(T));
-    pthread_setspecific(getKey(), storedValue);
-#endif
+    SWIFT_THREAD_SETSPECIFIC(key.getKey(), storedValue);
   }
 };
+#endif
+
 } // end namespace swift
 
 /// SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(TYPE, NAME) - Declare a variable
@@ -124,13 +161,16 @@ class ThreadLocal {
 ///
 /// Because of the fallback path, the default-initialization of the
 /// type must be equivalent to a bitwise zero-initialization, and the
-/// type must be small and trivially copyable.
+/// type must be small and trivially copyable and destructible.
 #if SWIFT_RUNTIME_SUPPORTS_THREAD_LOCAL
-#define SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(TYPE, NAME) \
+#define SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(TYPE, NAME, KEY) \
   SWIFT_RUNTIME_ATTRIBUTE_THREAD_LOCAL swift::ThreadLocal<TYPE> NAME
+#elif SWIFT_TLS_HAS_RESERVED_PTHREAD_SPECIFIC
+#define SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(TYPE, NAME, KEY) \
+  swift::ThreadLocal<TYPE, ConstantThreadLocalKey<KEY>> NAME
 #else
-#define SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(TYPE, NAME) \
-  swift::ThreadLocal<TYPE> NAME
+#define SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(TYPE, NAME, KEY) \
+  swift::ThreadLocal<TYPE, ThreadLocalKey> NAME
 #endif
 
 #endif

stdlib/public/runtime/ThreadLocalStorage.h renamed to include/swift/Runtime/ThreadLocalStorage.h

@@ -48,12 +48,33 @@ extern "C" int pthread_key_init_np(int key, void (*destructor)(void *));
 # ifndef __PTK_FRAMEWORK_SWIFT_KEY3
 #  define __PTK_FRAMEWORK_SWIFT_KEY3 103
 # endif
+# ifndef __PTK_FRAMEWORK_SWIFT_KEY4
+#  define __PTK_FRAMEWORK_SWIFT_KEY4 104
+# endif
+# ifndef __PTK_FRAMEWORK_SWIFT_KEY5
+#  define __PTK_FRAMEWORK_SWIFT_KEY5 105
+# endif
+# ifndef __PTK_FRAMEWORK_SWIFT_KEY6
+#  define __PTK_FRAMEWORK_SWIFT_KEY6 106
+# endif
+# ifndef __PTK_FRAMEWORK_SWIFT_KEY7
+#  define __PTK_FRAMEWORK_SWIFT_KEY7 107
+# endif
+# ifndef __PTK_FRAMEWORK_SWIFT_KEY8
+#  define __PTK_FRAMEWORK_SWIFT_KEY8 108
+# endif
+# ifndef __PTK_FRAMEWORK_SWIFT_KEY9
+#  define __PTK_FRAMEWORK_SWIFT_KEY9 109
+# endif
 
 
 # define SWIFT_RUNTIME_TLS_KEY __PTK_FRAMEWORK_SWIFT_KEY0
 # define SWIFT_STDLIB_TLS_KEY __PTK_FRAMEWORK_SWIFT_KEY1
 # define SWIFT_COMPATIBILITY_50_TLS_KEY __PTK_FRAMEWORK_SWIFT_KEY2
 # define SWIFT_CONCURRENCY_TASK_KEY __PTK_FRAMEWORK_SWIFT_KEY3
+# define SWIFT_CONCURRENCY_EXECUTOR_TRACKING_INFO_KEY __PTK_FRAMEWORK_SWIFT_KEY4
+# define SWIFT_CONCURRENCY_FALLBACK_TASK_LOCAL_STORAGE_KEY \
+  __PTK_FRAMEWORK_SWIFT_KEY5
 
 #endif
 

stdlib/public/Concurrency/Actor.cpp

@@ -26,12 +26,12 @@
 #endif
 
 #include "../CompatibilityOverride/CompatibilityOverride.h"
-#include "../runtime/ThreadLocalStorage.h"
 #include "swift/Runtime/Atomic.h"
 #include "swift/Runtime/Casting.h"
 #include "swift/Runtime/Once.h"
 #include "swift/Runtime/Mutex.h"
 #include "swift/Runtime/ThreadLocal.h"
+#include "swift/Runtime/ThreadLocalStorage.h"
 #include "swift/ABI/Task.h"
 #include "swift/ABI/Actor.h"
 #include "llvm/ADT/PointerIntPair.h"
@@ -111,8 +111,9 @@ class ExecutorTrackingInfo {
   /// the right executor. It would make sense for that to be a
   /// separate thread-local variable (or whatever is most efficient
   /// on the target platform).
-  static SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(Pointer<ExecutorTrackingInfo>,
-                                            ActiveInfoInThread);
+  static SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(
+      Pointer<ExecutorTrackingInfo>, ActiveInfoInThread,
+      SWIFT_CONCURRENCY_EXECUTOR_TRACKING_INFO_KEY);
 
   /// The active executor.
   ExecutorRef ActiveExecutor = ExecutorRef::generic();
@@ -186,21 +187,11 @@ class ExecutorTrackingInfo {
   }
 };
 
-#ifdef SWIFT_TLS_HAS_RESERVED_PTHREAD_SPECIFIC
-class ActiveTask {
-public:
-  static void set(AsyncTask *task) {
-    SWIFT_THREAD_SETSPECIFIC(SWIFT_CONCURRENCY_TASK_KEY, task);
-  }
-  static AsyncTask *get() {
-    return (AsyncTask *)SWIFT_THREAD_GETSPECIFIC(SWIFT_CONCURRENCY_TASK_KEY);
-  }
-};
-#else
 class ActiveTask {
   /// A thread-local variable pointing to the active tracking
   /// information about the current thread, if any.
-  static SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(Pointer<AsyncTask>, Value);
+  static SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(Pointer<AsyncTask>, Value,
+                                            SWIFT_CONCURRENCY_TASK_KEY);
 
 public:
   static void set(AsyncTask *task) { Value.set(task); }
@@ -210,11 +201,13 @@ class ActiveTask {
 /// Define the thread-locals.
 SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(
   Pointer<AsyncTask>,
-  ActiveTask::Value);
-#endif
+  ActiveTask::Value,
+  SWIFT_CONCURRENCY_TASK_KEY);
+
 SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(
   Pointer<ExecutorTrackingInfo>,
-  ExecutorTrackingInfo::ActiveInfoInThread);
+  ExecutorTrackingInfo::ActiveInfoInThread,
+  SWIFT_CONCURRENCY_EXECUTOR_TRACKING_INFO_KEY);
 
 } // end anonymous namespace
 

stdlib/public/Concurrency/TaskLocal.cpp

@@ -11,13 +11,13 @@
 //===----------------------------------------------------------------------===//
 
 #include "../CompatibilityOverride/CompatibilityOverride.h"
-#include "../runtime/ThreadLocalStorage.h"
 #include "swift/Runtime/Atomic.h"
 #include "swift/Runtime/Casting.h"
 #include "swift/Runtime/Once.h"
 #include "swift/Runtime/Mutex.h"
 #include "swift/Runtime/Concurrency.h"
 #include "swift/Runtime/ThreadLocal.h"
+#include "swift/Runtime/ThreadLocalStorage.h"
 #include "swift/ABI/TaskLocal.h"
 #include "swift/ABI/Task.h"
 #include "swift/ABI/Actor.h"
@@ -59,8 +59,8 @@ template <class T> struct Pointer {
 /// THIS IS RUNTIME INTERNAL AND NOT ABI.
 class FallbackTaskLocalStorage {
   static SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(
-      Pointer<TaskLocal::Storage>,
-      Value);
+      Pointer<TaskLocal::Storage>, Value,
+      SWIFT_CONCURRENCY_FALLBACK_TASK_LOCAL_STORAGE_KEY);
 
 public:
   static void set(TaskLocal::Storage *task) { Value.set(task); }
@@ -69,8 +69,8 @@ class FallbackTaskLocalStorage {
 
 /// Define the thread-locals.
 SWIFT_RUNTIME_DECLARE_THREAD_LOCAL(
-    Pointer<TaskLocal::Storage>,
-    FallbackTaskLocalStorage::Value);
+    Pointer<TaskLocal::Storage>, FallbackTaskLocalStorage::Value,
+    SWIFT_CONCURRENCY_FALLBACK_TASK_LOCAL_STORAGE_KEY);
 
 // ==== ABI --------------------------------------------------------------------
 

stdlib/public/runtime/Exclusivity.cpp

@@ -24,11 +24,11 @@
 
 #include "swift/Runtime/Exclusivity.h"
 #include "../SwiftShims/Visibility.h"
-#include "ThreadLocalStorage.h"
 #include "swift/Basic/Lazy.h"
 #include "swift/Runtime/Config.h"
 #include "swift/Runtime/Debug.h"
 #include "swift/Runtime/Metadata.h"
+#include "swift/Runtime/ThreadLocalStorage.h"
 #include <memory>
 #include <inttypes.h>
 #include <stdio.h>

stdlib/public/stubs/ThreadLocalStorage.cpp

@@ -13,9 +13,9 @@
 #include <cstring>
 
 #include "../SwiftShims/ThreadLocalStorage.h"
-#include "../runtime/ThreadLocalStorage.h"
 #include "swift/Basic/Lazy.h"
 #include "swift/Runtime/Debug.h"
+#include "swift/Runtime/ThreadLocalStorage.h"
 
 SWIFT_CC(swift) SWIFT_RUNTIME_STDLIB_API
 void _stdlib_destroyTLS(void *);

stdlib/toolchain/CompatibilityDynamicReplacements/DynamicReplaceable.cpp

@@ -19,7 +19,7 @@
 
 #include "swift/Runtime/Once.h"
 #include "swift/Runtime/Exclusivity.h"
-#include "../../public/runtime/ThreadLocalStorage.h"
+#include "swift/Runtime/ThreadLocalStorage.h"
 
 using namespace swift;