[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
Tue Nov 4 12:43:45 PST 2014
There is another thread discussing similar issues on PPC. I’m going to cc you into that thread too. I suspect we will need to use the hand rolled solution that is implemented for Windows on more platforms.
-Chris
> On Nov 4, 2014, at 12:12 AM, Jiangning Liu <liujiangning1 at gmail.com> wrote:
>
> BTW, my OS is debian and "uname -a" shows,
>
> Linux 3.15.0-rc8+ #9 SMP PREEMPT aarch64 GNU/Linux
>
> Thanks,
> -Jiangning
>
> 2014-11-04 16:09 GMT+08:00 Jiangning Liu <liujiangning1 at gmail.com <mailto:liujiangning1 at gmail.com>>:
> Hi Chris,
>
> This commit triggered a llvm/clang build failure on aarch64 host machine. The error message is like,
>
> /bin/sh: line 1: 16677 Segmentation fault ../../../../bin/clang-tblgen -gen-arm-neon -I /work/slave/performance-daily/build/tools/clang/lib/Headers -I /work/slave/performance-daily/build/lib/Target -I /work/slave/performance-daily/build/include /work/slave/performance-daily/build/tools/clang/include/clang/Basic/arm_neon.td <http://arm_neon.td/> -o /work/slave/performance-daily/build/build/tools/clang/lib/Headers/arm_neon.h.tmp
>
> It seems pthread doesn't work well on aarch64 target, so the following code doesn't work.
>
> +void llvm::call_once(once_flag& flag, void (*fptr)(void)) {
> + std::call_once(flag, fptr);
> +}
>
> Can we use the same solution as windows rather than call std::call_once directly?
>
> Thanks,
> -Jiangning
>
>
> 2014-10-31 6:07 GMT+08:00 Chris Bieneman <beanz at apple.com <mailto:beanz at apple.com>>:
> Author: cbieneman
> Date: Thu Oct 30 17:07:09 2014
> New Revision: 220932
>
> URL: http://llvm.org/viewvc/llvm-project?rev=220932&view=rev <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 <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 <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 <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 <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 <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 <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 <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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