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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 }
    131