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1 //= llvm/Support/Win32/Mutex.inc - Win32 Reader/Writer Mutual Exclusion Lock =//
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 the Win32 specific (non-pthread) RWMutex class.
11 //
12 //===----------------------------------------------------------------------===//
13
14 //===----------------------------------------------------------------------===//
15 //=== WARNING: Implementation here must contain only generic Win32 code that
16 //=== is guaranteed to work on *all* Win32 variants.
17 //===----------------------------------------------------------------------===//
18
19 #include "WindowsSupport.h"
20
21 namespace llvm {
22 using namespace sys;
23
24 // Windows has slim read-writer lock support on Vista and higher, so we
25 // will attempt to load the APIs. If they exist, we will use them, and
26 // if not, we will fall back on critical sections. When we drop support
27 // for XP, we can stop lazy-loading these APIs and just use them directly.
28 #if defined(__MINGW32__)
29 // Taken from WinNT.h
30 typedef struct _RTL_SRWLOCK {
31 PVOID Ptr;
32 } RTL_SRWLOCK, *PRTL_SRWLOCK;
33
34 // Taken from WinBase.h
35 typedef RTL_SRWLOCK SRWLOCK, *PSRWLOCK;
36 #endif
37
38 static VOID (WINAPI *fpInitializeSRWLock)(PSRWLOCK lock) = NULL;
39 static VOID (WINAPI *fpAcquireSRWLockExclusive)(PSRWLOCK lock) = NULL;
40 static VOID (WINAPI *fpAcquireSRWLockShared)(PSRWLOCK lock) = NULL;
41 static VOID (WINAPI *fpReleaseSRWLockExclusive)(PSRWLOCK lock) = NULL;
42 static VOID (WINAPI *fpReleaseSRWLockShared)(PSRWLOCK lock) = NULL;
43
44 static bool sHasSRW = false;
45
46 static bool loadSRW() {
47 static bool sChecked = false;
48 if (!sChecked) {
49 sChecked = true;
50
51 if (HMODULE hLib = ::GetModuleHandleW(L"Kernel32.dll")) {
52 fpInitializeSRWLock =
53 (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
54 "InitializeSRWLock");
55 fpAcquireSRWLockExclusive =
56 (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
57 "AcquireSRWLockExclusive");
58 fpAcquireSRWLockShared =
59 (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
60 "AcquireSRWLockShared");
61 fpReleaseSRWLockExclusive =
62 (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
63 "ReleaseSRWLockExclusive");
64 fpReleaseSRWLockShared =
65 (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
66 "ReleaseSRWLockShared");
67
68 if (fpInitializeSRWLock != NULL) {
69 sHasSRW = true;
70 }
71 }
72 }
73 return sHasSRW;
74 }
75
76 RWMutexImpl::RWMutexImpl() {
77 if (loadSRW()) {
78 data_ = calloc(1, sizeof(SRWLOCK));
79 fpInitializeSRWLock(static_cast<PSRWLOCK>(data_));
80 } else {
81 data_ = calloc(1, sizeof(CRITICAL_SECTION));
82 InitializeCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
83 }
84 }
85
86 RWMutexImpl::~RWMutexImpl() {
87 if (!sHasSRW)
88 DeleteCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
89 // Nothing to do in the case of slim reader/writers except free the memory.
90 free(data_);
91 }
92
93 bool RWMutexImpl::reader_acquire() {
94 if (sHasSRW) {
95 fpAcquireSRWLockShared(static_cast<PSRWLOCK>(data_));
96 } else {
97 EnterCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
98 }
99 return true;
100 }
101
102 bool RWMutexImpl::reader_release() {
103 if (sHasSRW) {
104 fpReleaseSRWLockShared(static_cast<PSRWLOCK>(data_));
105 } else {
106 LeaveCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
107 }
108 return true;
109 }
110
111 bool RWMutexImpl::writer_acquire() {
112 if (sHasSRW) {
113 fpAcquireSRWLockExclusive(static_cast<PSRWLOCK>(data_));
114 } else {
115 EnterCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
116 }
117 return true;
118 }
119
120 bool RWMutexImpl::writer_release() {
121 if (sHasSRW) {
122 fpReleaseSRWLockExclusive(static_cast<PSRWLOCK>(data_));
123 } else {
124 LeaveCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
125 }
126 return true;
127 }
128
129
130 }