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/Support/Atomic.h"
16 #include "llvm/Support/Mutex.h"
17 #include "llvm/Config/config.h"
18 #include <cassert>
19 
20 using namespace llvm;
21 
22 static bool multithreaded_mode = false;
23 
24 static sys::Mutex* global_lock = 0;
25 
26 bool llvm::llvm_start_multithreaded() {
27 #ifdef LLVM_MULTITHREADED
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 
41 void llvm::llvm_stop_multithreaded() {
42 #ifdef LLVM_MULTITHREADED
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 
54 bool llvm::llvm_is_multithreaded() {
55   return multithreaded_mode;
56 }
57 
58 void llvm::llvm_acquire_global_lock() {
59   if (multithreaded_mode) global_lock->acquire();
60 }
61 
62 void llvm::llvm_release_global_lock() {
63   if (multithreaded_mode) global_lock->release();
64 }
65 
66 #if defined(LLVM_MULTITHREADED) && defined(HAVE_PTHREAD_H)
67 #include <pthread.h>
68 
69 struct ThreadInfo {
70   void (*UserFn)(void *);
71   void *UserData;
72 };
73 static void *ExecuteOnThread_Dispatch(void *Arg) {
74   ThreadInfo *TI = reinterpret_cast<ThreadInfo*>(Arg);
75   TI->UserFn(TI->UserData);
76   return 0;
77 }
78 
79 void 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, 0);
101 
102  error:
103   ::pthread_attr_destroy(&Attr);
104 }
105 
106 #else
107 
108 // No non-pthread implementation, currently.
109 
110 void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
111                                   unsigned RequestedStackSize) {
112   (void) RequestedStackSize;
113   Fn(UserData);
114 }
115 
116 #endif
117