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semaphore_test.cc
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semaphore_test.cc
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// Copyright 2017 The Cobalt Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <unistd.h>
#include "starboard/common/semaphore.h"
#include "starboard/common/time.h"
#include "starboard/nplb/posix_compliance/posix_thread_helpers.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace starboard {
namespace nplb {
TEST(Semaphore, PutAndTake) {
Semaphore semaphore;
semaphore.Put();
semaphore.Take();
EXPECT_FALSE(semaphore.TakeTry());
}
TEST(Semaphore, PutAndTakeTry) {
Semaphore semaphore;
semaphore.Put();
EXPECT_TRUE(semaphore.TakeTry());
}
// Tests the expectation that waiting no time will succeed
// If the semaphore is uncontended.
TEST(Semaphore, TakeWait_Zero) {
Semaphore semaphore;
semaphore.Put();
EXPECT_TRUE(semaphore.TakeWait(0));
}
TEST(Semaphore, InitialValue_One) {
Semaphore semaphore(1);
semaphore.Take();
EXPECT_FALSE(semaphore.TakeTry());
}
class ThreadTakesSemaphore : public posix::AbstractTestThread {
public:
explicit ThreadTakesSemaphore(Semaphore* s) : semaphore_(s) {}
void Run() override { semaphore_->Take(); }
private:
Semaphore* semaphore_;
};
TEST(Semaphore, ThreadTakes) {
Semaphore semaphore;
ThreadTakesSemaphore thread(&semaphore);
thread.Start();
semaphore.Put();
thread.Join();
}
class ThreadTakesWaitSemaphore : public posix::AbstractTestThread {
public:
explicit ThreadTakesWaitSemaphore(int64_t wait_us)
: thread_started_(false),
wait_us_(wait_us),
result_signaled_(false),
result_wait_time_(0) {}
void Run() override {
thread_started_ = true;
int64_t start_time = CurrentMonotonicTime();
result_signaled_ = semaphore_.TakeWait(wait_us_);
result_wait_time_ = CurrentMonotonicTime() - start_time;
}
// Use a volatile bool to signal when the thread has started executing
// instead of a semaphore since some platforms may take a relatively long
// time after signalling the semaphore to return from the Put.
volatile bool thread_started_;
int64_t wait_us_;
Semaphore semaphore_;
bool result_signaled_;
int64_t result_wait_time_;
};
TEST(Semaphore, FLAKY_ThreadTakesWait_PutBeforeTimeExpires) {
int64_t timeout_time = 250'000; // 250ms
int64_t wait_time = 1000; // 1ms
ThreadTakesWaitSemaphore thread(timeout_time);
// Create thread and wait for it to start executing.
thread.Start();
while (!thread.thread_started_) {
usleep(1000);
}
usleep(wait_time);
thread.semaphore_.Put();
thread.Join();
EXPECT_TRUE(thread.result_signaled_);
EXPECT_LT(thread.result_wait_time_, timeout_time);
}
double IsDoubleNear(double first, double second, double diff_threshold) {
double diff = first - second;
if (diff < 0) {
diff = -diff;
}
return diff < diff_threshold;
}
TEST(Semaphore, ThreadTakesWait_TimeExpires) {
const int attempts = 20; // Retest up to 20 times.
bool passed = false;
const int64_t kTimeThreshold = 5'000; // 5ms
for (int i = 0; i < attempts; ++i) {
int64_t wait_time = 20'000; // 20ms
ThreadTakesWaitSemaphore thread(wait_time);
// Create thread and wait for it to start executing.
thread.Start();
while (!thread.thread_started_) {
usleep(1000);
}
// It is possible for the thread to be preempted just before processing
// Semaphore::TakeWait, so sleep for an extra amount of time to avoid the
// semaphore being legitimately signalled during the wait time (because
// the thread started TakeWait late).
usleep(wait_time * 5);
thread.semaphore_.Put();
thread.Join();
EXPECT_FALSE(thread.result_signaled_);
if (IsDoubleNear(1.0 * wait_time, 1.0 * thread.result_wait_time_,
kTimeThreshold * 1.0)) {
return; // Test passed.
}
}
EXPECT_TRUE(false) << "Thread waited, but time exceeded expectations.";
}
class ThreadPutsSemaphore : public posix::AbstractTestThread {
public:
explicit ThreadPutsSemaphore(Semaphore* s) : semaphore_(s) {}
void Run() override { semaphore_->Put(); }
private:
Semaphore* semaphore_;
};
TEST(Semaphore, ThreadPuts) {
Semaphore semaphore;
ThreadPutsSemaphore thread(&semaphore);
thread.Start();
thread.Join();
semaphore.Put();
}
} // namespace nplb
} // namespace starboard