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/*
* Copyright 2015 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "../private/SkLeanWindows.h"
#include "../private/SkSemaphore.h"
#if defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_IOS)
#include <mach/mach.h>
// We've got to teach TSAN that there is a happens-before edge beteween
// semaphore_signal() and semaphore_wait().
#if __has_feature(thread_sanitizer)
extern "C" void AnnotateHappensBefore(const char*, int, void*);
extern "C" void AnnotateHappensAfter (const char*, int, void*);
#else
static void AnnotateHappensBefore(const char*, int, void*) {}
static void AnnotateHappensAfter (const char*, int, void*) {}
#endif
struct SkBaseSemaphore::OSSemaphore {
semaphore_t fSemaphore;
OSSemaphore() {
semaphore_create(mach_task_self(), &fSemaphore, SYNC_POLICY_LIFO, 0/*initial count*/);
}
~OSSemaphore() { semaphore_destroy(mach_task_self(), fSemaphore); }
void signal(int n) {
while (n --> 0) {
AnnotateHappensBefore(__FILE__, __LINE__, &fSemaphore);
semaphore_signal(fSemaphore);
}
}
void wait() {
semaphore_wait(fSemaphore);
AnnotateHappensAfter(__FILE__, __LINE__, &fSemaphore);
}
};
#elif defined(SK_BUILD_FOR_WIN)
struct SkBaseSemaphore::OSSemaphore {
HANDLE fSemaphore;
OSSemaphore() {
fSemaphore = CreateSemaphore(nullptr /*security attributes, optional*/,
0 /*initial count*/,
MAXLONG /*max count*/,
nullptr /*name, optional*/);
}
~OSSemaphore() { CloseHandle(fSemaphore); }
void signal(int n) {
ReleaseSemaphore(fSemaphore, n, nullptr/*returns previous count, optional*/);
}
void wait() { WaitForSingleObject(fSemaphore, INFINITE/*timeout in ms*/); }
};
#else
// It's important we test for Mach before this. This code will compile but not work there.
#include <errno.h>
#include <semaphore.h>
struct SkBaseSemaphore::OSSemaphore {
sem_t fSemaphore;
OSSemaphore() { sem_init(&fSemaphore, 0/*cross process?*/, 0/*initial count*/); }
~OSSemaphore() { sem_destroy(&fSemaphore); }
void signal(int n) { while (n --> 0) { sem_post(&fSemaphore); } }
void wait() {
// Try until we're not interrupted.
while(sem_wait(&fSemaphore) == -1 && errno == EINTR);
}
};
#endif
///////////////////////////////////////////////////////////////////////////////
void SkBaseSemaphore::osSignal(int n) {
fOSSemaphoreOnce([this] { fOSSemaphore = new OSSemaphore; });
fOSSemaphore->signal(n);
}
void SkBaseSemaphore::osWait() {
fOSSemaphoreOnce([this] { fOSSemaphore = new OSSemaphore; });
fOSSemaphore->wait();
}
void SkBaseSemaphore::cleanup() {
delete fOSSemaphore;
}
bool SkBaseSemaphore::try_wait() {
int count = fCount.load(std::memory_order_relaxed);
if (count > 0) {
return fCount.compare_exchange_weak(count, count-1, std::memory_order_acquire);
}
return false;
}
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