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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 "Windows.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     HMODULE hLib = ::LoadLibrary(TEXT("Kernel32"));
     52     if (hLib) {
     53       fpInitializeSRWLock =
     54         (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
     55                                                "InitializeSRWLock");
     56       fpAcquireSRWLockExclusive =
     57         (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
     58                                                "AcquireSRWLockExclusive");
     59       fpAcquireSRWLockShared =
     60         (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
     61                                                "AcquireSRWLockShared");
     62       fpReleaseSRWLockExclusive =
     63         (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
     64                                                "ReleaseSRWLockExclusive");
     65       fpReleaseSRWLockShared =
     66         (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
     67                                                "ReleaseSRWLockShared");
     68       ::FreeLibrary(hLib);
     69 
     70       if (fpInitializeSRWLock != NULL) {
     71         sHasSRW = true;
     72       }
     73     }
     74   }
     75   return sHasSRW;
     76 }
     77 
     78 RWMutexImpl::RWMutexImpl() {
     79   if (loadSRW()) {
     80     data_ = calloc(1, sizeof(SRWLOCK));
     81     fpInitializeSRWLock(static_cast<PSRWLOCK>(data_));
     82   } else {
     83     data_ = calloc(1, sizeof(CRITICAL_SECTION));
     84     InitializeCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
     85   }
     86 }
     87 
     88 RWMutexImpl::~RWMutexImpl() {
     89   if (sHasSRW) {
     90     // Nothing to do in the case of slim reader/writers
     91   } else {
     92     DeleteCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
     93     free(data_);
     94   }
     95 }
     96 
     97 bool RWMutexImpl::reader_acquire() {
     98   if (sHasSRW) {
     99     fpAcquireSRWLockShared(static_cast<PSRWLOCK>(data_));
    100   } else {
    101     EnterCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
    102   }
    103   return true;
    104 }
    105 
    106 bool RWMutexImpl::reader_release() {
    107   if (sHasSRW) {
    108     fpReleaseSRWLockShared(static_cast<PSRWLOCK>(data_));
    109   } else {
    110     LeaveCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
    111   }
    112   return true;
    113 }
    114 
    115 bool RWMutexImpl::writer_acquire() {
    116   if (sHasSRW) {
    117     fpAcquireSRWLockExclusive(static_cast<PSRWLOCK>(data_));
    118   } else {
    119     EnterCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
    120   }
    121   return true;
    122 }
    123 
    124 bool RWMutexImpl::writer_release() {
    125   if (sHasSRW) {
    126     fpReleaseSRWLockExclusive(static_cast<PSRWLOCK>(data_));
    127   } else {
    128     LeaveCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
    129   }
    130   return true;
    131 }
    132 
    133 
    134 }
    135