[Support] Base SmartMutex on std::recursive_mutex

- Remove support for non-recursive mutexes. This was unused.
- The std::recursive_mutex is now created/destroyed unconditionally.
  Locking is still only done if threading is enabled.
- Alias SmartScopedLock to std::lock_guard.

This should make no semantic difference on the existing APIs.

llvm-svn: 368158

include/llvm/Support/Mutex.h

@@ -13,97 +13,31 @@
 #ifndef LLVM_SUPPORT_MUTEX_H
 #define LLVM_SUPPORT_MUTEX_H
 
-#include "llvm/Config/llvm-config.h"
-#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Threading.h"
 #include <cassert>
+#include <mutex>
 
 namespace llvm
 {
   namespace sys
   {
-    /// Platform agnostic Mutex class.
-    class MutexImpl
-    {
-    /// @name Constructors
-    /// @{
-    public:
-
-      /// Initializes the lock but doesn't acquire it. if \p recursive is set
-      /// to false, the lock will not be recursive which makes it cheaper but
-      /// also more likely to deadlock (same thread can't acquire more than
-      /// once).
-      /// Default Constructor.
-      explicit MutexImpl(bool recursive = true);
-
-      /// Releases and removes the lock
-      /// Destructor
-      ~MutexImpl();
-
-    /// @}
-    /// @name Methods
-    /// @{
-    public:
-
-      /// Attempts to unconditionally acquire the lock. If the lock is held by
-      /// another thread, this method will wait until it can acquire the lock.
-      /// @returns false if any kind of error occurs, true otherwise.
-      /// Unconditionally acquire the lock.
-      bool acquire();
-
-      /// Attempts to release the lock. If the lock is held by the current
-      /// thread, the lock is released allowing other threads to acquire the
-      /// lock.
-      /// @returns false if any kind of error occurs, true otherwise.
-      /// Unconditionally release the lock.
-      bool release();
-
-      /// Attempts to acquire the lock without blocking. If the lock is not
-      /// available, this function returns false quickly (without blocking). If
-      /// the lock is available, it is acquired.
-      /// @returns false if any kind of error occurs or the lock is not
-      /// available, true otherwise.
-      /// Try to acquire the lock.
-      bool tryacquire();
-
-    //@}
-    /// @name Platform Dependent Data
-    /// @{
-    private:
-#if defined(LLVM_ENABLE_THREADS) && LLVM_ENABLE_THREADS != 0
-      void* data_; ///< We don't know what the data will be
-#endif
-
-    /// @}
-    /// @name Do Not Implement
-    /// @{
-    private:
-      MutexImpl(const MutexImpl &) = delete;
-      void operator=(const MutexImpl &) = delete;
-    /// @}
-    };
-
-
     /// SmartMutex - A mutex with a compile time constant parameter that
     /// indicates whether this mutex should become a no-op when we're not
     /// running in multithreaded mode.
     template<bool mt_only>
     class SmartMutex {
-      MutexImpl impl;
-      unsigned acquired;
-      bool recursive;
-    public:
-      explicit SmartMutex(bool rec = true) :
-        impl(rec), acquired(0), recursive(rec) { }
+      std::recursive_mutex impl;
+      unsigned acquired = 0;
 
+    public:
       bool lock() {
         if (!mt_only || llvm_is_multithreaded()) {
-          return impl.acquire();
+          impl.lock();
+          return true;
         } else {
           // Single-threaded debugging code.  This would be racy in
           // multithreaded mode, but provides not sanity checks in single
           // threaded mode.
-          assert((recursive || acquired == 0) && "Lock already acquired!!");
           ++acquired;
           return true;
         }
@@ -111,13 +45,13 @@ namespace llvm
 
       bool unlock() {
         if (!mt_only || llvm_is_multithreaded()) {
-          return impl.release();
+          impl.unlock();
+          return true;
         } else {
           // Single-threaded debugging code.  This would be racy in
           // multithreaded mode, but provides not sanity checks in single
           // threaded mode.
-          assert(((recursive && acquired) || (acquired == 1)) &&
-                 "Lock not acquired before release!");
+          assert(acquired && "Lock not acquired before release!");
           --acquired;
           return true;
         }
@@ -125,31 +59,16 @@ namespace llvm
 
       bool try_lock() {
         if (!mt_only || llvm_is_multithreaded())
-          return impl.tryacquire();
+          return impl.try_lock();
         else return true;
       }
-
-      private:
-        SmartMutex(const SmartMutex<mt_only> & original);
-        void operator=(const SmartMutex<mt_only> &);
     };
 
     /// Mutex - A standard, always enforced mutex.
     typedef SmartMutex<false> Mutex;
 
-    template<bool mt_only>
-    class SmartScopedLock  {
-      SmartMutex<mt_only>& mtx;
-
-    public:
-      SmartScopedLock(SmartMutex<mt_only>& m) : mtx(m) {
-        mtx.lock();
-      }
-
-      ~SmartScopedLock() {
-        mtx.unlock();
-      }
-    };
+    template <bool mt_only>
+    using SmartScopedLock = std::lock_guard<SmartMutex<mt_only>>;
 
     typedef SmartScopedLock<false> ScopedLock;
   }

lib/Support/CMakeLists.txt

@@ -170,7 +170,6 @@ add_llvm_library(LLVMSupport
   Errno.cpp
   Host.cpp
   Memory.cpp
-  Mutex.cpp
   Path.cpp
   Process.cpp
   Program.cpp

lib/Support/Mutex.cpp

@@ -1,123 +0,0 @@
-//===- Mutex.cpp - Mutual Exclusion Lock ------------------------*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements the llvm::sys::Mutex class.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Support/Mutex.h"
-#include "llvm/Config/config.h"
-#include "llvm/Support/ErrorHandling.h"
-
-//===----------------------------------------------------------------------===//
-//=== WARNING: Implementation here must contain only TRULY operating system
-//===          independent code.
-//===----------------------------------------------------------------------===//
-
-#if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
-// Define all methods as no-ops if threading is explicitly disabled
-namespace llvm {
-using namespace sys;
-MutexImpl::MutexImpl( bool recursive) { }
-MutexImpl::~MutexImpl() { }
-bool MutexImpl::acquire() { return true; }
-bool MutexImpl::release() { return true; }
-bool MutexImpl::tryacquire() { return true; }
-}
-#else
-
-#if defined(HAVE_PTHREAD_H) && defined(HAVE_PTHREAD_MUTEX_LOCK)
-
-#include <cassert>
-#include <pthread.h>
-#include <stdlib.h>
-
-namespace llvm {
-using namespace sys;
-
-// Construct a Mutex using pthread calls
-MutexImpl::MutexImpl( bool recursive)
-  : data_(nullptr)
-{
-  // Declare the pthread_mutex data structures
-  pthread_mutex_t* mutex =
-    static_cast<pthread_mutex_t*>(safe_malloc(sizeof(pthread_mutex_t)));
-
-  pthread_mutexattr_t attr;
-
-  // Initialize the mutex attributes
-  int errorcode = pthread_mutexattr_init(&attr);
-  assert(errorcode == 0); (void)errorcode;
-
-  // Initialize the mutex as a recursive mutex, if requested, or normal
-  // otherwise.
-  int kind = ( recursive  ? PTHREAD_MUTEX_RECURSIVE : PTHREAD_MUTEX_NORMAL );
-  errorcode = pthread_mutexattr_settype(&attr, kind);
-  assert(errorcode == 0);
-
-  // Initialize the mutex
-  errorcode = pthread_mutex_init(mutex, &attr);
-  assert(errorcode == 0);
-
-  // Destroy the attributes
-  errorcode = pthread_mutexattr_destroy(&attr);
-  assert(errorcode == 0);
-
-  // Assign the data member
-  data_ = mutex;
-}
-
-// Destruct a Mutex
-MutexImpl::~MutexImpl()
-{
-  pthread_mutex_t* mutex = static_cast<pthread_mutex_t*>(data_);
-  assert(mutex != nullptr);
-  pthread_mutex_destroy(mutex);
-  free(mutex);
-}
-
-bool
-MutexImpl::acquire()
-{
-  pthread_mutex_t* mutex = static_cast<pthread_mutex_t*>(data_);
-  assert(mutex != nullptr);
-
-  int errorcode = pthread_mutex_lock(mutex);
-  return errorcode == 0;
-}
-
-bool
-MutexImpl::release()
-{
-  pthread_mutex_t* mutex = static_cast<pthread_mutex_t*>(data_);
-  assert(mutex != nullptr);
-
-  int errorcode = pthread_mutex_unlock(mutex);
-  return errorcode == 0;
-}
-
-bool
-MutexImpl::tryacquire()
-{
-  pthread_mutex_t* mutex = static_cast<pthread_mutex_t*>(data_);
-  assert(mutex != nullptr);
-
-  int errorcode = pthread_mutex_trylock(mutex);
-  return errorcode == 0;
-}
-
-}
-
-#elif defined(LLVM_ON_UNIX)
-#include "Unix/Mutex.inc"
-#elif defined( _WIN32)
-#include "Windows/Mutex.inc"
-#else
-#warning Neither LLVM_ON_UNIX nor _WIN32 was set in Support/Mutex.cpp
-#endif
-#endif

lib/Support/Unix/Mutex.inc

@@ -1,42 +0,0 @@
-//===- llvm/Support/Unix/Mutex.inc - Unix Mutex Implementation ---*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements the Unix specific (non-pthread) Mutex class.
-//
-//===----------------------------------------------------------------------===//
-
-//===----------------------------------------------------------------------===//
-//=== WARNING: Implementation here must contain only generic UNIX code that
-//===          is guaranteed to work on *all* UNIX variants.
-//===----------------------------------------------------------------------===//
-
-namespace llvm
-{
-using namespace sys;
-
-MutexImpl::MutexImpl( bool recursive)
-{
-}
-
-MutexImpl::~MutexImpl()
-{
-}
-
-bool
-MutexImpl::release()
-{
-  return true;
-}
-
-bool
-MutexImpl::tryacquire( void )
-{
-  return true;
-}
-
-}

lib/Support/Windows/Mutex.inc

@@ -1,56 +0,0 @@
-//===- llvm/Support/Win32/Mutex.inc - Win32 Mutex Implementation -*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements the Win32 specific (non-pthread) Mutex class.
-//
-//===----------------------------------------------------------------------===//
-
-//===----------------------------------------------------------------------===//
-//=== WARNING: Implementation here must contain only generic Win32 code that
-//===          is guaranteed to work on *all* Win32 variants.
-//===----------------------------------------------------------------------===//
-
-#include "WindowsSupport.h"
-#include "llvm/Support/Mutex.h"
-
-namespace llvm {
-
-sys::MutexImpl::MutexImpl(bool /*recursive*/)
-{
-  data_ = new CRITICAL_SECTION;
-  InitializeCriticalSection((LPCRITICAL_SECTION)data_);
-}
-
-sys::MutexImpl::~MutexImpl()
-{
-  DeleteCriticalSection((LPCRITICAL_SECTION)data_);
-  delete (LPCRITICAL_SECTION)data_;
-  data_ = 0;
-}
-
-bool
-sys::MutexImpl::acquire()
-{
-  EnterCriticalSection((LPCRITICAL_SECTION)data_);
-  return true;
-}
-
-bool
-sys::MutexImpl::release()
-{
-  LeaveCriticalSection((LPCRITICAL_SECTION)data_);
-  return true;
-}
-
-bool
-sys::MutexImpl::tryacquire()
-{
-  return TryEnterCriticalSection((LPCRITICAL_SECTION)data_);
-}
-
-}