// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
******************************************************************************
*
* Copyright (C) 1997-2016, International Business Machines
* Corporation and others. All Rights Reserved.
*
******************************************************************************
*
* File umutex.cpp
*
* Modification History:
*
* Date Name Description
* 04/02/97 aliu Creation.
* 04/07/99 srl updated
* 05/13/99 stephen Changed to umutex (from cmutex).
* 11/22/99 aliu Make non-global mutex autoinitialize [j151]
******************************************************************************
*/
#include "umutex.h"
#include "unicode/utypes.h"
#include "uassert.h"
#include "cmemory.h"
// The ICU global mutex. Used when ICU implementation code passes NULL for the mutex pointer.
static UMutex globalMutex = U_MUTEX_INITIALIZER;
/*
* ICU Mutex wrappers. Wrap operating system mutexes, giving the rest of ICU a
* platform independent set of mutex operations. For internal ICU use only.
*/
#if defined(U_USER_MUTEX_CPP)
// Build time user mutex hook: #include "U_USER_MUTEX_CPP"
#include U_MUTEX_XSTR(U_USER_MUTEX_CPP)
#elif U_PLATFORM_USES_ONLY_WIN32_API
#if defined U_NO_PLATFORM_ATOMICS
#error ICU on Win32 requires support for low level atomic operations.
// Visual Studio, gcc, clang are OK. Shouldn't get here.
#endif
// This function is called when a test of a UInitOnce::fState reveals that
// initialization has not completed, that we either need to call the
// function on this thread, or wait for some other thread to complete.
//
// The actual call to the init function is made inline by template code
// that knows the C++ types involved. This function returns TRUE if
// the caller needs to call the Init function.
//
U_NAMESPACE_BEGIN
U_COMMON_API UBool U_EXPORT2 umtx_initImplPreInit(UInitOnce &uio) {
for (;;) {
int32_t previousState = InterlockedCompareExchange(
(LONG volatile *) // this is the type given in the API doc for this function.
&uio.fState, // Destination
1, // Exchange Value
0); // Compare value
if (previousState == 0) {
return true; // Caller will next call the init function.
// Current state == 1.
} else if (previousState == 2) {
// Another thread already completed the initialization.
// We can simply return FALSE, indicating no
// further action is needed by the caller.
return FALSE;
} else {
// Another thread is currently running the initialization.
// Wait until it completes.
do {
Sleep(1);
previousState = umtx_loadAcquire(uio.fState);
} while (previousState == 1);
}
}
}
// This function is called by the thread that ran an initialization function,
// just after completing the function.
U_COMMON_API void U_EXPORT2 umtx_initImplPostInit(UInitOnce &uio) {
umtx_storeRelease(uio.fState, 2);
}
U_NAMESPACE_END
static void winMutexInit(CRITICAL_SECTION *cs) {
InitializeCriticalSection(cs);
return;
}
U_CAPI void U_EXPORT2
umtx_lock(UMutex *mutex) {
if (mutex == NULL) {
mutex = &globalMutex;
}
CRITICAL_SECTION *cs = &mutex->fCS;
umtx_initOnce(mutex->fInitOnce, winMutexInit, cs);
EnterCriticalSection(cs);
}
U_CAPI void U_EXPORT2
umtx_unlock(UMutex* mutex)
{
if (mutex == NULL) {
mutex = &globalMutex;
}
LeaveCriticalSection(&mutex->fCS);
}
U_CAPI void U_EXPORT2
umtx_condBroadcast(UConditionVar *condition) {
// We require that the associated mutex be held by the caller,
// so access to fWaitCount is protected and safe. No other thread can
// call condWait() while we are here.
if (condition->fWaitCount == 0) {
return;
}
ResetEvent(condition->fExitGate);
SetEvent(condition->fEntryGate);
}
U_CAPI void U_EXPORT2
umtx_condSignal(UConditionVar * /* condition */) {
// Function not implemented. There is no immediate requirement from ICU to have it.
// Once ICU drops support for Windows XP and Server 2003, ICU Condition Variables will be
// changed to be thin wrappers on native Windows CONDITION_VARIABLEs, and this function
// becomes trivial to provide.
U_ASSERT(FALSE);
}
U_CAPI void U_EXPORT2
umtx_condWait(UConditionVar *condition, UMutex *mutex) {
if (condition->fEntryGate == NULL) {
// Note: because the associated mutex must be locked when calling
// wait, we know that there can not be multiple threads
// running here with the same condition variable.
// Meaning that lazy initialization is safe.
U_ASSERT(condition->fExitGate == NULL);
condition->fEntryGate = CreateEvent(NULL, // Security Attributes
TRUE, // Manual Reset
FALSE, // Initially reset
NULL); // Name.
U_ASSERT(condition->fEntryGate != NULL);
condition->fExitGate = CreateEvent(NULL, TRUE, TRUE, NULL);
U_ASSERT(condition->fExitGate != NULL);
}
condition->fWaitCount++;
umtx_unlock(mutex);
WaitForSingleObject(condition->fEntryGate, INFINITE);
umtx_lock(mutex);
condition->fWaitCount--;
if (condition->fWaitCount == 0) {
// All threads that were waiting at the entry gate have woken up
// and moved through. Shut the entry gate and open the exit gate.
ResetEvent(condition->fEntryGate);
SetEvent(condition->fExitGate);
} else {
umtx_unlock(mutex);
WaitForSingleObject(condition->fExitGate, INFINITE);
umtx_lock(mutex);
}
}
#elif U_PLATFORM_IMPLEMENTS_POSIX
//-------------------------------------------------------------------------------------------
//
// POSIX specific definitions
//
//-------------------------------------------------------------------------------------------
# include <pthread.h>
// Each UMutex consists of a pthread_mutex_t.
// All are statically initialized and ready for use.
// There is no runtime mutex initialization code needed.
U_CAPI void U_EXPORT2
umtx_lock(UMutex *mutex) {
if (mutex == NULL) {
mutex = &globalMutex;
}
int sysErr = pthread_mutex_lock(&mutex->fMutex);
(void)sysErr; // Suppress unused variable warnings.
U_ASSERT(sysErr == 0);
}
U_CAPI void U_EXPORT2
umtx_unlock(UMutex* mutex)
{
if (mutex == NULL) {
mutex = &globalMutex;
}
int sysErr = pthread_mutex_unlock(&mutex->fMutex);
(void)sysErr; // Suppress unused variable warnings.
U_ASSERT(sysErr == 0);
}
U_CAPI void U_EXPORT2
umtx_condWait(UConditionVar *cond, UMutex *mutex) {
if (mutex == NULL) {
mutex = &globalMutex;
}
int sysErr = pthread_cond_wait(&cond->fCondition, &mutex->fMutex);
(void)sysErr;
U_ASSERT(sysErr == 0);
}
U_CAPI void U_EXPORT2
umtx_condBroadcast(UConditionVar *cond) {
int sysErr = pthread_cond_broadcast(&cond->fCondition);
(void)sysErr;
U_ASSERT(sysErr == 0);
}
U_CAPI void U_EXPORT2
umtx_condSignal(UConditionVar *cond) {
int sysErr = pthread_cond_signal(&cond->fCondition);
(void)sysErr;
U_ASSERT(sysErr == 0);
}
U_NAMESPACE_BEGIN
static pthread_mutex_t initMutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t initCondition = PTHREAD_COND_INITIALIZER;
// This function is called when a test of a UInitOnce::fState reveals that
// initialization has not completed, that we either need to call the
// function on this thread, or wait for some other thread to complete.
//
// The actual call to the init function is made inline by template code
// that knows the C++ types involved. This function returns TRUE if
// the caller needs to call the Init function.
//
U_COMMON_API UBool U_EXPORT2
umtx_initImplPreInit(UInitOnce &uio) {
pthread_mutex_lock(&initMutex);
int32_t state = uio.fState;
if (state == 0) {
umtx_storeRelease(uio.fState, 1);
pthread_mutex_unlock(&initMutex);
return TRUE; // Caller will next call the init function.
} else {
while (uio.fState == 1) {
// Another thread is currently running the initialization.
// Wait until it completes.
pthread_cond_wait(&initCondition, &initMutex);
}
pthread_mutex_unlock(&initMutex);
U_ASSERT(uio.fState == 2);
return FALSE;
}
}
// This function is called by the thread that ran an initialization function,
// just after completing the function.
// Some threads may be waiting on the condition, requiring the broadcast wakeup.
// Some threads may be racing to test the fState variable outside of the mutex,
// requiring the use of store/release when changing its value.
U_COMMON_API void U_EXPORT2
umtx_initImplPostInit(UInitOnce &uio) {
pthread_mutex_lock(&initMutex);
umtx_storeRelease(uio.fState, 2);
pthread_cond_broadcast(&initCondition);
pthread_mutex_unlock(&initMutex);
}
U_NAMESPACE_END
// End of POSIX specific umutex implementation.
#else // Platform #define chain.
#error Unknown Platform
#endif // Platform #define chain.
//-------------------------------------------------------------------------------
//
// Atomic Operations, out-of-line versions.
// These are conditional, only defined if better versions
// were not available for the platform.
//
// These versions are platform neutral.
//
//--------------------------------------------------------------------------------
#if defined U_NO_PLATFORM_ATOMICS
static UMutex gIncDecMutex = U_MUTEX_INITIALIZER;
U_NAMESPACE_BEGIN
U_COMMON_API int32_t U_EXPORT2
umtx_atomic_inc(u_atomic_int32_t *p) {
int32_t retVal;
umtx_lock(&gIncDecMutex);
retVal = ++(*p);
umtx_unlock(&gIncDecMutex);
return retVal;
}
U_COMMON_API int32_t U_EXPORT2
umtx_atomic_dec(u_atomic_int32_t *p) {
int32_t retVal;
umtx_lock(&gIncDecMutex);
retVal = --(*p);
umtx_unlock(&gIncDecMutex);
return retVal;
}
U_COMMON_API int32_t U_EXPORT2
umtx_loadAcquire(u_atomic_int32_t &var) {
umtx_lock(&gIncDecMutex);
int32_t val = var;
umtx_unlock(&gIncDecMutex);
return val;
}
U_COMMON_API void U_EXPORT2
umtx_storeRelease(u_atomic_int32_t &var, int32_t val) {
umtx_lock(&gIncDecMutex);
var = val;
umtx_unlock(&gIncDecMutex);
}
U_NAMESPACE_END
#endif
//--------------------------------------------------------------------------
//
// Deprecated functions for setting user mutexes.
//
//--------------------------------------------------------------------------
U_DEPRECATED void U_EXPORT2
u_setMutexFunctions(const void * /*context */, UMtxInitFn *, UMtxFn *,
UMtxFn *, UMtxFn *, UErrorCode *status) {
if (U_SUCCESS(*status)) {
*status = U_UNSUPPORTED_ERROR;
}
return;
}
U_DEPRECATED void U_EXPORT2
u_setAtomicIncDecFunctions(const void * /*context */, UMtxAtomicFn *, UMtxAtomicFn *,
UErrorCode *status) {
if (U_SUCCESS(*status)) {
*status = U_UNSUPPORTED_ERROR;
}
return;
}