[llvm] r220932 - Removing the static initializer in ManagedStatic.cpp by using llvm_call_once to initialize the ManagedStatic mutex.
Chris Bieneman
beanz at apple.com
Thu Oct 30 15:07:09 PDT 2014
Author: cbieneman
Date: Thu Oct 30 17:07:09 2014
New Revision: 220932
URL: http://llvm.org/viewvc/llvm-project?rev=220932&view=rev
Log:
Removing the static initializer in ManagedStatic.cpp by using llvm_call_once to initialize the ManagedStatic mutex.
Summary:
This patch adds an llvm_call_once which is a wrapper around std::call_once on platforms where it is available and devoid of bugs. The patch also migrates the ManagedStatic mutex to be allocated using llvm_call_once.
These changes are philosophically equivalent to the changes added in r219638, which were reverted due to a hang on Win32 which was the result of a bug in the Windows implementation of std::call_once.
Reviewers: aaron.ballman, chapuni, chandlerc, rnk
Reviewed By: rnk
Subscribers: majnemer, llvm-commits
Differential Revision: http://reviews.llvm.org/D5922
Added:
llvm/trunk/lib/Support/Unix/Threading.inc
llvm/trunk/lib/Support/Windows/Threading.inc
Modified:
llvm/trunk/include/llvm/Support/Threading.h
llvm/trunk/lib/Support/CMakeLists.txt
llvm/trunk/lib/Support/ManagedStatic.cpp
llvm/trunk/lib/Support/Threading.cpp
Modified: llvm/trunk/include/llvm/Support/Threading.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Threading.h?rev=220932&r1=220931&r2=220932&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/Threading.h (original)
+++ llvm/trunk/include/llvm/Support/Threading.h Thu Oct 30 17:07:09 2014
@@ -15,6 +15,14 @@
#ifndef LLVM_SUPPORT_THREADING_H
#define LLVM_SUPPORT_THREADING_H
+#include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
+
+#if defined(LLVM_ON_UNIX)
+#include <mutex>
+#else
+#include "llvm/Support/Atomic.h"
+#endif
+
namespace llvm {
/// Returns true if LLVM is compiled with support for multi-threading, and
/// false otherwise.
@@ -33,6 +41,35 @@ namespace llvm {
/// the thread stack.
void llvm_execute_on_thread(void (*UserFn)(void*), void *UserData,
unsigned RequestedStackSize = 0);
+
+#if defined(LLVM_ON_UNIX)
+typedef std::once_flag once_flag;
+#define LLVM_DEFINE_ONCE_FLAG(flag) static once_flag flag
+#else
+enum InitStatus {
+ Done = -1,
+ Uninitialized = 0,
+ Wait = 1
+};
+typedef volatile sys::cas_flag once_flag;
+
+#define LLVM_DEFINE_ONCE_FLAG(flag) static once_flag flag = Uninitialized
+#endif
+
+/// \brief Execute the function specified as a parameter once.
+///
+/// Typical usage:
+/// \code
+/// void foo() {...};
+/// ...
+/// LLVM_DEFINE_ONCE_FLAG(flag);
+/// call_once(flag, foo);
+/// \endcode
+///
+/// \param flag Flag used for tracking whether or not this has run.
+/// \param UserFn Function to call once.
+void call_once(once_flag&, void (*)(void));
+
}
#endif
Modified: llvm/trunk/lib/Support/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/CMakeLists.txt?rev=220932&r1=220931&r2=220932&view=diff
==============================================================================
--- llvm/trunk/lib/Support/CMakeLists.txt (original)
+++ llvm/trunk/lib/Support/CMakeLists.txt Thu Oct 30 17:07:09 2014
@@ -102,6 +102,7 @@ add_llvm_library(LLVMSupport
Unix/Program.inc
Unix/RWMutex.inc
Unix/Signals.inc
+ Unix/Threading.inc
Unix/ThreadLocal.inc
Unix/TimeValue.inc
Unix/Watchdog.inc
@@ -114,6 +115,7 @@ add_llvm_library(LLVMSupport
Windows/Program.inc
Windows/RWMutex.inc
Windows/Signals.inc
+ Windows/Threading.inc
Windows/ThreadLocal.inc
Windows/TimeValue.inc
Windows/Watchdog.inc
Modified: llvm/trunk/lib/Support/ManagedStatic.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/ManagedStatic.cpp?rev=220932&r1=220931&r2=220932&view=diff
==============================================================================
--- llvm/trunk/lib/Support/ManagedStatic.cpp (original)
+++ llvm/trunk/lib/Support/ManagedStatic.cpp Thu Oct 30 17:07:09 2014
@@ -16,16 +16,23 @@
#include "llvm/Support/Atomic.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/MutexGuard.h"
+#include "llvm/Support/Threading.h"
#include <cassert>
using namespace llvm;
static const ManagedStaticBase *StaticList = nullptr;
+static sys::Mutex *ManagedStaticMutex = nullptr;
+LLVM_DEFINE_ONCE_FLAG(mutex_init_flag);
-static sys::Mutex& getManagedStaticMutex() {
+static void initializeMutex() {
+ ManagedStaticMutex = new sys::Mutex();
+}
+
+static sys::Mutex* getManagedStaticMutex() {
// We need to use a function local static here, since this can get called
// during a static constructor and we need to guarantee that it's initialized
// correctly.
- static sys::Mutex ManagedStaticMutex;
+ call_once(mutex_init_flag, initializeMutex);
return ManagedStaticMutex;
}
@@ -33,7 +40,7 @@ void ManagedStaticBase::RegisterManagedS
void (*Deleter)(void*)) const {
assert(Creator);
if (llvm_is_multithreaded()) {
- MutexGuard Lock(getManagedStaticMutex());
+ MutexGuard Lock(*getManagedStaticMutex());
if (!Ptr) {
void* tmp = Creator();
@@ -83,7 +90,7 @@ void ManagedStaticBase::destroy() const
/// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
void llvm::llvm_shutdown() {
- MutexGuard Lock(getManagedStaticMutex());
+ MutexGuard Lock(*getManagedStaticMutex());
while (StaticList)
StaticList->destroy();
Modified: llvm/trunk/lib/Support/Threading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Threading.cpp?rev=220932&r1=220931&r2=220932&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Threading.cpp (original)
+++ llvm/trunk/lib/Support/Threading.cpp Thu Oct 30 17:07:09 2014
@@ -110,3 +110,10 @@ void llvm::llvm_execute_on_thread(void (
}
#endif
+
+#if defined(LLVM_ON_UNIX)
+#include "Unix/Threading.inc"
+#else
+#include "Windows/Threading.inc"
+#endif
+
Added: llvm/trunk/lib/Support/Unix/Threading.inc
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Unix/Threading.inc?rev=220932&view=auto
==============================================================================
--- llvm/trunk/lib/Support/Unix/Threading.inc (added)
+++ llvm/trunk/lib/Support/Unix/Threading.inc Thu Oct 30 17:07:09 2014
@@ -0,0 +1,5 @@
+#include <thread>
+
+void llvm::call_once(once_flag& flag, void (*fptr)(void)) {
+ std::call_once(flag, fptr);
+}
Added: llvm/trunk/lib/Support/Windows/Threading.inc
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Windows/Threading.inc?rev=220932&view=auto
==============================================================================
--- llvm/trunk/lib/Support/Windows/Threading.inc (added)
+++ llvm/trunk/lib/Support/Windows/Threading.inc Thu Oct 30 17:07:09 2014
@@ -0,0 +1,19 @@
+#include <winbase.h>
+
+void llvm::call_once(once_flag &flag, void (*fptr)(void)) {
+ while (flag != Done) {
+ if (flag == Wait) {
+ ::Sleep(1);
+ continue;
+ }
+
+ sys::cas_flag old_val = sys::CompareAndSwap(&flag, Wait, Uninitialized);
+ if (old_val == Uninitialized) {
+ fptr();
+ sys::MemoryFence();
+ flag = Done;
+ return;
+ }
+ }
+ sys::MemoryFence();
+}
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