Threading.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f 
1//===-- llvm/Support/Threading.cpp- Control multithreading mode --*- C++ -*-==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements llvm_start_multithreaded() and friends.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Support/Threading.h"
15#include "llvm/Config/config.h"
16#include "llvm/Support/Atomic.h"
17#include "llvm/Support/Mutex.h"
18#include <cassert>
19
20using namespace llvm;
21
22static bool multithreaded_mode = false;
23
24static sys::Mutex* global_lock = nullptr;
25
26bool llvm::llvm_start_multithreaded() {
27#if LLVM_ENABLE_THREADS != 0
28  assert(!multithreaded_mode && "Already multithreaded!");
29  multithreaded_mode = true;
30  global_lock = new sys::Mutex(true);
31
32  // We fence here to ensure that all initialization is complete BEFORE we
33  // return from llvm_start_multithreaded().
34  sys::MemoryFence();
35  return true;
36#else
37  return false;
38#endif
39}
40
41void llvm::llvm_stop_multithreaded() {
42#if LLVM_ENABLE_THREADS != 0
43  assert(multithreaded_mode && "Not currently multithreaded!");
44
45  // We fence here to insure that all threaded operations are complete BEFORE we
46  // return from llvm_stop_multithreaded().
47  sys::MemoryFence();
48
49  multithreaded_mode = false;
50  delete global_lock;
51#endif
52}
53
54bool llvm::llvm_is_multithreaded() {
55  return multithreaded_mode;
56}
57
58void llvm::llvm_acquire_global_lock() {
59  if (multithreaded_mode) global_lock->acquire();
60}
61
62void llvm::llvm_release_global_lock() {
63  if (multithreaded_mode) global_lock->release();
64}
65
66#if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
67#include <pthread.h>
68
69struct ThreadInfo {
70  void (*UserFn)(void *);
71  void *UserData;
72};
73static void *ExecuteOnThread_Dispatch(void *Arg) {
74  ThreadInfo *TI = reinterpret_cast<ThreadInfo*>(Arg);
75  TI->UserFn(TI->UserData);
76  return nullptr;
77}
78
79void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
80                                  unsigned RequestedStackSize) {
81  ThreadInfo Info = { Fn, UserData };
82  pthread_attr_t Attr;
83  pthread_t Thread;
84
85  // Construct the attributes object.
86  if (::pthread_attr_init(&Attr) != 0)
87    return;
88
89  // Set the requested stack size, if given.
90  if (RequestedStackSize != 0) {
91    if (::pthread_attr_setstacksize(&Attr, RequestedStackSize) != 0)
92      goto error;
93  }
94
95  // Construct and execute the thread.
96  if (::pthread_create(&Thread, &Attr, ExecuteOnThread_Dispatch, &Info) != 0)
97    goto error;
98
99  // Wait for the thread and clean up.
100  ::pthread_join(Thread, nullptr);
101
102 error:
103  ::pthread_attr_destroy(&Attr);
104}
105#elif LLVM_ENABLE_THREADS!=0 && defined(LLVM_ON_WIN32)
106#include "Windows/WindowsSupport.h"
107#include <process.h>
108
109struct ThreadInfo {
110  void (*func)(void*);
111  void *param;
112};
113
114static unsigned __stdcall ThreadCallback(void *param) {
115  struct ThreadInfo *info = reinterpret_cast<struct ThreadInfo *>(param);
116  info->func(info->param);
117
118  return 0;
119}
120
121void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
122                                  unsigned RequestedStackSize) {
123  struct ThreadInfo param = { Fn, UserData };
124
125  HANDLE hThread = (HANDLE)::_beginthreadex(NULL,
126                                            RequestedStackSize, ThreadCallback,
127                                            &param, 0, NULL);
128
129  if (hThread) {
130    // We actually don't care whether the wait succeeds or fails, in
131    // the same way we don't care whether the pthread_join call succeeds
132    // or fails.  There's not much we could do if this were to fail. But
133    // on success, this call will wait until the thread finishes executing
134    // before returning.
135    (void)::WaitForSingleObject(hThread, INFINITE);
136    ::CloseHandle(hThread);
137  }
138}
139#else
140// Support for non-Win32, non-pthread implementation.
141void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
142                                  unsigned RequestedStackSize) {
143  (void) RequestedStackSize;
144  Fn(UserData);
145}
146
147#endif
148