llvm-project/lldb/source/Host/windows/ProcessRunLock.cpp

#ifdef _WIN32

#include "lldb/Host/ProcessRunLock.h"
#include "lldb/Host/windows/windows.h"

namespace lldb_private {

    // Windows has slim read-writer lock support on Vista and higher, so we
    // will attempt to load the APIs.  If they exist, we will use them, and
    // if not, we will fall back on critical sections.  When we drop support
    // for XP, we can stop lazy-loading these APIs and just use them directly.
#if defined(__MINGW32__)
    // Taken from WinNT.h
    typedef struct _RTL_SRWLOCK {
        PVOID Ptr;
    } RTL_SRWLOCK, *PRTL_SRWLOCK;

    // Taken from WinBase.h
    typedef RTL_SRWLOCK SRWLOCK, *PSRWLOCK;
#endif


    typedef struct Win32RWLOCK
    {
        unsigned long int readlockcount;
        HANDLE writable;
        CRITICAL_SECTION writelock;
        unsigned long int writelocked;
    } Win32RWLOCK;

    typedef Win32RWLOCK* PWin32RWLOCK;

    static VOID (WINAPI *fpInitializeSRWLock)(PSRWLOCK lock) = NULL;
    static VOID (WINAPI *fpAcquireSRWLockExclusive)(PSRWLOCK lock) = NULL;
    static VOID (WINAPI *fpAcquireSRWLockShared)(PSRWLOCK lock) = NULL;
    static VOID (WINAPI *fpReleaseSRWLockExclusive)(PSRWLOCK lock) = NULL;
    static VOID (WINAPI *fpReleaseSRWLockShared)(PSRWLOCK lock) = NULL;
    static BOOL (WINAPI *fpTryAcquireSRWLockExclusive)(PSRWLOCK lock) = NULL;
    static BOOL (WINAPI *fpTryAcquireSRWLockShared)(PSRWLOCK lock) = NULL;

    static bool sHasSRW = false;

    static bool loadSRW()
    {
        static bool sChecked = false;
        if (!sChecked)
        {
            sChecked = true;
            return false;

            HMODULE hLib = ::LoadLibrary(TEXT("Kernel32"));
            if (hLib)
            {
                fpInitializeSRWLock =
                    (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
                    "InitializeSRWLock");
                fpAcquireSRWLockExclusive =
                    (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
                    "AcquireSRWLockExclusive");
                fpAcquireSRWLockShared =
                    (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
                    "AcquireSRWLockShared");
                fpReleaseSRWLockExclusive =
                    (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
                    "ReleaseSRWLockExclusive");
                fpReleaseSRWLockShared =
                    (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
                    "ReleaseSRWLockShared");
                fpTryAcquireSRWLockExclusive =
                    (BOOL (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
                    "TryAcquireSRWLockExclusive");
                fpTryAcquireSRWLockShared =
                    (BOOL (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
                    "TryAcquireSRWLockShared");

                ::FreeLibrary(hLib);

                if (fpInitializeSRWLock != NULL) {
                    sHasSRW = true;
                }
            }
        }
        return sHasSRW;
    }

    ProcessRunLock::ProcessRunLock ()
        : m_running(false)
    {
        if (loadSRW())
        {
            m_rwlock = calloc(1, sizeof(SRWLOCK));
            fpInitializeSRWLock(static_cast<PSRWLOCK>(m_rwlock));
        }
        else
        {
            m_rwlock = calloc(1, sizeof(Win32RWLOCK));
            static_cast<PWin32RWLOCK>(m_rwlock)->readlockcount = 0;
            static_cast<PWin32RWLOCK>(m_rwlock)->writable = CreateEvent(NULL, true, true, NULL);
            InitializeCriticalSection(&static_cast<PWin32RWLOCK>(m_rwlock)->writelock);
        }
    }

    ProcessRunLock::~ProcessRunLock ()
    {
        if (!sHasSRW)
        {
            CloseHandle(static_cast<PWin32RWLOCK>(m_rwlock)->writable);
            DeleteCriticalSection(&static_cast<PWin32RWLOCK>(m_rwlock)->writelock);
        }
        free(m_rwlock);
    }

    bool ReadLock (lldb::rwlock_t rwlock)
    {
        if (sHasSRW)
        {
            fpAcquireSRWLockShared(static_cast<PSRWLOCK>(rwlock));
            return true;
        }
        else
        {
            EnterCriticalSection(&static_cast<PWin32RWLOCK>(rwlock)->writelock);
            InterlockedIncrement(&static_cast<PWin32RWLOCK>(rwlock)->readlockcount);
            ResetEvent(static_cast<PWin32RWLOCK>(rwlock)->writable);
            LeaveCriticalSection(&static_cast<PWin32RWLOCK>(rwlock)->writelock);
            return true;
        }
    }

    bool ProcessRunLock::ReadTryLock ()
    {
        ReadLock(m_rwlock);
        if (m_running == false)
            return true;
        ReadUnlock();
        return false;
    }

    bool ProcessRunLock::ReadUnlock ()
    {
        if (sHasSRW)
        {
            fpReleaseSRWLockShared(static_cast<PSRWLOCK>(m_rwlock));
            return true;
        }
        else
        {
            unsigned long int value = InterlockedDecrement(&static_cast<PWin32RWLOCK>(m_rwlock)->readlockcount);
            assert(((int)value) >= 0);
            if (value == 0)
                SetEvent(static_cast<PWin32RWLOCK>(m_rwlock)->writable);
            return true;
        }
    }

    bool WriteLock(lldb::rwlock_t rwlock)
    {
        if (sHasSRW)
        {
            fpAcquireSRWLockExclusive(static_cast<PSRWLOCK>(rwlock));
            return true;
        }
        else
        {
            EnterCriticalSection(&static_cast<PWin32RWLOCK>(rwlock)->writelock);
            WaitForSingleObject(static_cast<PWin32RWLOCK>(rwlock)->writable, INFINITE);
            int res = InterlockedExchange(&static_cast<PWin32RWLOCK>(rwlock)->writelocked, 1);
            assert(res == 0);
            return true;
        }
    }

    bool WriteTryLock(lldb::rwlock_t rwlock)
    {
        if (sHasSRW)
        {
            return fpTryAcquireSRWLockExclusive(static_cast<PSRWLOCK>(rwlock)) != 0;
        }
        else
        {
            if (TryEnterCriticalSection(&static_cast<PWin32RWLOCK>(rwlock)->writelock)) {
                if (WaitForSingleObject(static_cast<PWin32RWLOCK>(rwlock)->writable, 0)) {
                    LeaveCriticalSection(&static_cast<PWin32RWLOCK>(rwlock)->writelock);
                    return false;
                }
                int res = InterlockedExchange(&static_cast<PWin32RWLOCK>(rwlock)->writelocked, 1);
                assert(res == 0);
                return true;
            }
            return false;
        }
    }

    bool WriteUnlock(lldb::rwlock_t rwlock)
    {
        if (sHasSRW)
        {
            fpReleaseSRWLockExclusive(static_cast<PSRWLOCK>(rwlock));
            return true;
        }
        else
        {
            int res = InterlockedExchange(&static_cast<PWin32RWLOCK>(rwlock)->writelocked, 0);
            if (res == 1) {
                LeaveCriticalSection(&static_cast<PWin32RWLOCK>(rwlock)->writelock);
                return true;
            }
            return false;
        }
    }

    bool ProcessRunLock::SetRunning ()
    {
        WriteLock(m_rwlock);
        m_running = true;
        WriteUnlock(m_rwlock);
        return true;
    }

    bool ProcessRunLock::TrySetRunning ()
    {
        if (WriteTryLock(m_rwlock))
        {
            bool r = !m_running;
            m_running = true;
            WriteUnlock(m_rwlock);
            return r;
        }
        return false;
    }

    bool ProcessRunLock::SetStopped ()
    {
        WriteLock(m_rwlock);
        m_running = false;
        WriteUnlock(m_rwlock);
        return true;
    }
}

#endif