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// Copyright 2021 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <signal.h>
#include "src/base/platform/mutex.h"
#include "src/base/platform/platform.h"
#include "src/base/platform/time.h"
#include "src/base/utils/random-number-generator.h"
#include "src/libsampler/sampler.h" // for USE_SIGNALS
#include "test/cctest/cctest.h"
namespace v8 {
namespace sampler {
// There seem to be problems with pthread_rwlock_t and signal handling on
// Mac, see https://crbug.com/v8/11399 and
// https://stackoverflow.com/questions/22643374/deadlock-with-pthread-rwlock-t-and-signals
// This test reproduces it, and can be used to test if this problem is fixed in
// future Mac releases.
#ifdef USE_SIGNALS
void HandleProfilerSignal(int signal, siginfo_t*, void*) {
CHECK_EQ(SIGPROF, signal);
}
struct sigaction old_signal_handler;
void InstallSignalHandler() {
struct sigaction sa;
sa.sa_sigaction = &HandleProfilerSignal;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
CHECK_EQ(0, sigaction(SIGPROF, &sa, &old_signal_handler));
}
static void RestoreSignalHandler() {
sigaction(SIGPROF, &old_signal_handler, nullptr);
}
TEST(SignalsPlusSharedMutexes) {
static constexpr int kNumMutexes = 1024;
// 10us * 10000 = 100ms
static constexpr auto kSleepBetweenSamples =
base::TimeDelta::FromMicroseconds(10);
static constexpr size_t kNumSamples = 10000;
// Keep a set of all currently running threads. This is filled by the threads
// themselves, because we need to get their pthread id.
base::Mutex threads_mutex;
std::set<pthread_t> threads_to_sample;
auto SendSignalToThreads = [&threads_mutex, &threads_to_sample] {
base::MutexGuard guard(&threads_mutex);
for (pthread_t tid : threads_to_sample) {
pthread_kill(tid, SIGPROF);
}
};
auto AddThreadToSample = [&threads_mutex, &threads_to_sample](pthread_t tid) {
base::MutexGuard guard(&threads_mutex);
CHECK(threads_to_sample.insert(tid).second);
};
auto RemoveThreadToSample = [&threads_mutex,
&threads_to_sample](pthread_t tid) {
base::MutexGuard guard(&threads_mutex);
CHECK_EQ(1, threads_to_sample.erase(tid));
};
// The sampling threads periodically sends a SIGPROF to all running threads.
class SamplingThread : public base::Thread {
public:
explicit SamplingThread(std::atomic<size_t>* remaining_samples,
std::function<void()> send_signal_to_threads)
: Thread(base::Thread::Options{"SamplingThread"}),
remaining_samples_(remaining_samples),
send_signal_to_threads_(std::move(send_signal_to_threads)) {}
void Run() override {
DCHECK_LT(0, remaining_samples_->load(std::memory_order_relaxed));
while (remaining_samples_->fetch_sub(1, std::memory_order_relaxed) > 1) {
send_signal_to_threads_();
base::OS::Sleep(kSleepBetweenSamples);
}
DCHECK_EQ(0, remaining_samples_->load(std::memory_order_relaxed));
}
private:
std::atomic<size_t>* const remaining_samples_;
const std::function<void()> send_signal_to_threads_;
};
// These threads repeatedly lock and unlock a shared mutex, both in shared and
// exclusive mode. This should not deadlock.
class SharedMutexTestThread : public base::Thread {
public:
SharedMutexTestThread(
base::SharedMutex* mutexes, std::atomic<size_t>* remaining_samples,
int64_t rng_seed, std::function<void(pthread_t)> add_thread_to_sample,
std::function<void(pthread_t)> remove_thread_to_sample)
: Thread(Thread::Options{"SharedMutexTestThread"}),
mutexes_(mutexes),
remaining_samples_(remaining_samples),
rng_(rng_seed),
add_thread_to_sample_(add_thread_to_sample),
remove_thread_to_sample_(remove_thread_to_sample) {}
void Run() override {
add_thread_to_sample_(pthread_self());
while (remaining_samples_->load(std::memory_order_relaxed) > 0) {
size_t idx = rng_.NextInt(kNumMutexes);
base::SharedMutex* mutex = &mutexes_[idx];
if (rng_.NextBool()) {
base::SharedMutexGuard<base::kShared> guard{mutex};
} else {
base::SharedMutexGuard<base::kExclusive> guard{mutex};
}
}
remove_thread_to_sample_(pthread_self());
}
private:
base::SharedMutex* mutexes_;
std::atomic<size_t>* remaining_samples_;
base::RandomNumberGenerator rng_;
std::function<void(pthread_t)> add_thread_to_sample_;
std::function<void(pthread_t)> remove_thread_to_sample_;
};
std::atomic<size_t> remaining_samples{kNumSamples};
base::SharedMutex mutexes[kNumMutexes];
InstallSignalHandler();
auto* rng = CcTest::i_isolate()->random_number_generator();
// First start the mutex threads, then the sampling thread.
std::vector<std::unique_ptr<SharedMutexTestThread>> threads(4);
for (auto& thread : threads) {
thread = std::make_unique<SharedMutexTestThread>(
mutexes, &remaining_samples, rng->NextInt64(), AddThreadToSample,
RemoveThreadToSample);
CHECK(thread->Start());
}
SamplingThread sampling_thread(&remaining_samples, SendSignalToThreads);
CHECK(sampling_thread.Start());
// Wait for the sampling thread to be done. The mutex threads should finish
// shortly after.
sampling_thread.Join();
for (auto& thread : threads) thread->Join();
RestoreSignalHandler();
}
#endif // USE_SIGNALS
} // namespace sampler
} // namespace v8
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