From 63ce00b72f2420852a9d5dcb5b025d3320b7b989 Mon Sep 17 00:00:00 2001
From: Zachary Turner <zturner@google.com>
Date: Tue, 10 Jun 2014 23:15:43 +0000
Subject: Revert "Remove support for runtime multi-threading."

This reverts revision r210600.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210603 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Support/ErrorHandling.cpp |  8 ++------
 lib/Support/ManagedStatic.cpp |  6 ++++--
 lib/Support/Threading.cpp     | 41 ++++++++++++++++++++++++++++++++++++-----
 lib/Support/Timer.cpp         |  3 ++-
 4 files changed, 44 insertions(+), 14 deletions(-)

(limited to 'lib/Support')

diff --git a/lib/Support/ErrorHandling.cpp b/lib/Support/ErrorHandling.cpp
index b9e4eabe92..342c4f05cc 100644
--- a/lib/Support/ErrorHandling.cpp
+++ b/lib/Support/ErrorHandling.cpp
@@ -23,7 +23,6 @@
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
 #include <cstdlib>
-#include <mutex>
 
 #if defined(HAVE_UNISTD_H)
 # include <unistd.h>
@@ -38,18 +37,16 @@ using namespace llvm;
 static fatal_error_handler_t ErrorHandler = nullptr;
 static void *ErrorHandlerUserData = nullptr;
 
-static llvm::recursive_mutex ErrorHandlerMutex;
-
 void llvm::install_fatal_error_handler(fatal_error_handler_t handler,
                                        void *user_data) {
-  std::lock_guard<llvm::recursive_mutex> Lock(ErrorHandlerMutex);
+  assert(!llvm_is_multithreaded() &&
+         "Cannot register error handlers after starting multithreaded mode!\n");
   assert(!ErrorHandler && "Error handler already registered!\n");
   ErrorHandler = handler;
   ErrorHandlerUserData = user_data;
 }
 
 void llvm::remove_fatal_error_handler() {
-  std::lock_guard<llvm::recursive_mutex> Lock(ErrorHandlerMutex);
   ErrorHandler = nullptr;
 }
 
@@ -66,7 +63,6 @@ void llvm::report_fatal_error(StringRef Reason, bool GenCrashDiag) {
 }
 
 void llvm::report_fatal_error(const Twine &Reason, bool GenCrashDiag) {
-  std::lock_guard<llvm::recursive_mutex> Lock(ErrorHandlerMutex);
   if (ErrorHandler) {
     ErrorHandler(ErrorHandlerUserData, Reason.str(), GenCrashDiag);
   } else {
diff --git a/lib/Support/ManagedStatic.cpp b/lib/Support/ManagedStatic.cpp
index 74884d9330..6a1c2a545a 100644
--- a/lib/Support/ManagedStatic.cpp
+++ b/lib/Support/ManagedStatic.cpp
@@ -15,7 +15,6 @@
 #include "llvm/Config/config.h"
 #include "llvm/Support/Atomic.h"
 #include <cassert>
-#include <mutex>
 using namespace llvm;
 
 static const ManagedStaticBase *StaticList = nullptr;
@@ -24,7 +23,7 @@ void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
                                               void (*Deleter)(void*)) const {
   assert(Creator);
   if (llvm_is_multithreaded()) {
-    std::lock_guard<llvm::recursive_mutex> Lock(llvm_get_global_lock());
+    llvm_acquire_global_lock();
 
     if (!Ptr) {
       void* tmp = Creator();
@@ -45,6 +44,7 @@ void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
       StaticList = this;
     }
 
+    llvm_release_global_lock();
   } else {
     assert(!Ptr && !DeleterFn && !Next &&
            "Partially initialized ManagedStatic!?");
@@ -77,4 +77,6 @@ void ManagedStaticBase::destroy() const {
 void llvm::llvm_shutdown() {
   while (StaticList)
     StaticList->destroy();
+
+  if (llvm_is_multithreaded()) llvm_stop_multithreaded();
 }
diff --git a/lib/Support/Threading.cpp b/lib/Support/Threading.cpp
index c9f0f2c2e5..1acfa79b11 100644
--- a/lib/Support/Threading.cpp
+++ b/lib/Support/Threading.cpp
@@ -19,19 +19,50 @@
 
 using namespace llvm;
 
-llvm::recursive_mutex& llvm::llvm_get_global_lock() {
-  static llvm::recursive_mutex global_lock;
-  return global_lock;
-}
+static bool multithreaded_mode = false;
 
-bool llvm::llvm_is_multithreaded() {
+static sys::Mutex* global_lock = nullptr;
+
+bool llvm::llvm_start_multithreaded() {
 #if LLVM_ENABLE_THREADS != 0
+  assert(!multithreaded_mode && "Already multithreaded!");
+  multithreaded_mode = true;
+  global_lock = new sys::Mutex(true);
+
+  // We fence here to ensure that all initialization is complete BEFORE we
+  // return from llvm_start_multithreaded().
+  sys::MemoryFence();
   return true;
 #else
   return false;
 #endif
 }
 
+void llvm::llvm_stop_multithreaded() {
+#if LLVM_ENABLE_THREADS != 0
+  assert(multithreaded_mode && "Not currently multithreaded!");
+
+  // We fence here to insure that all threaded operations are complete BEFORE we
+  // return from llvm_stop_multithreaded().
+  sys::MemoryFence();
+
+  multithreaded_mode = false;
+  delete global_lock;
+#endif
+}
+
+bool llvm::llvm_is_multithreaded() {
+  return multithreaded_mode;
+}
+
+void llvm::llvm_acquire_global_lock() {
+  if (multithreaded_mode) global_lock->acquire();
+}
+
+void llvm::llvm_release_global_lock() {
+  if (multithreaded_mode) global_lock->release();
+}
+
 #if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
 #include <pthread.h>
 
diff --git a/lib/Support/Timer.cpp b/lib/Support/Timer.cpp
index cdab02b2fb..61465ae5e8 100644
--- a/lib/Support/Timer.cpp
+++ b/lib/Support/Timer.cpp
@@ -84,13 +84,14 @@ static TimerGroup *getDefaultTimerGroup() {
   sys::MemoryFence();
   if (tmp) return tmp;
   
-  std::lock_guard<llvm::recursive_mutex> Lock(llvm::llvm_get_global_lock());
+  llvm_acquire_global_lock();
   tmp = DefaultTimerGroup;
   if (!tmp) {
     tmp = new TimerGroup("Miscellaneous Ungrouped Timers");
     sys::MemoryFence();
     DefaultTimerGroup = tmp;
   }
+  llvm_release_global_lock();
 
   return tmp;
 }
-- 
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