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// Copyright 2019 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 "starboard/shared/pthread/thread_sampler_internal.h"
#if SB_API_VERSION >= SB_THREAD_SAMPLER_VERSION
#include <semaphore.h>
#include <signal.h>
#include "starboard/mutex.h"
#include "starboard/shared/pthread/thread_context_internal.h"
#include "starboard/thread.h"
namespace {
class SignalHandler {
public:
static void AddSampler() {
starboard::ScopedLock lock(GetMutex());
if (++sampler_count_ == 1) {
Install();
}
}
static void RemoveSampler() {
starboard::ScopedLock lock(GetMutex());
if (--sampler_count_ == 0) {
Restore();
}
}
static SbThreadContext Freeze(SbThreadSampler sampler);
static bool Thaw(SbThreadSampler sampler);
private:
// Getter with static local to lazily initialize the mutex once.
static const starboard::Mutex& GetMutex() {
static starboard::Mutex mutex;
return mutex;
}
static void Install() {
sem_init(&freeze_semaphore_, 0, 0);
sem_init(&thaw_semaphore_, 0, 0);
struct sigaction sa;
sa.sa_sigaction = &HandleProfilerSignal;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART | SA_SIGINFO;
signal_handler_installed_ =
(sigaction(SIGPROF, &sa, &old_signal_handler_) == 0);
}
static void Restore() {
if (signal_handler_installed_) {
sigaction(SIGPROF, &old_signal_handler_, 0);
signal_handler_installed_ = false;
}
sem_destroy(&freeze_semaphore_);
sem_destroy(&thaw_semaphore_);
}
static void HandleProfilerSignal(int signal, siginfo_t* info, void* context);
static int sampler_count_;
static bool signal_handler_installed_;
static struct sigaction old_signal_handler_;
static SbThreadContextPrivate sb_context_;
static SbThreadSampler frozen_sampler_;
// POSIX semaphore can be used in signal handler. Other synchronization,
// including mutex, condition variable and Starboard's semaphore can't.
static sem_t freeze_semaphore_;
static sem_t thaw_semaphore_;
};
int SignalHandler::sampler_count_ = 0;
bool SignalHandler::signal_handler_installed_ = false;
struct sigaction SignalHandler::old_signal_handler_;
SbThreadContextPrivate SignalHandler::sb_context_;
SbThreadSampler SignalHandler::frozen_sampler_ = kSbThreadSamplerInvalid;
sem_t SignalHandler::freeze_semaphore_;
sem_t SignalHandler::thaw_semaphore_;
SbThreadContext SignalHandler::Freeze(SbThreadSampler sampler) {
starboard::ScopedLock lock(GetMutex());
SB_DCHECK(frozen_sampler_ != sampler) << "SbThreadSampler frozen twice.";
if (!signal_handler_installed_ || SbThreadSamplerIsValid(frozen_sampler_)) {
return kSbThreadContextInvalid;
}
frozen_sampler_ = sampler;
pthread_kill(sampler->thread(), SIGPROF);
sem_wait(&freeze_semaphore_);
return &sb_context_;
}
bool SignalHandler::Thaw(SbThreadSampler sampler) {
starboard::ScopedLock lock(GetMutex());
SB_DCHECK(frozen_sampler_ == sampler) << "SbThreadSampler didn't freeze.";
if (frozen_sampler_ != sampler) return false;
sb_context_.ucontext = nullptr;
sem_post(&thaw_semaphore_);
frozen_sampler_ = kSbThreadSamplerInvalid;
return true;
}
void SignalHandler::HandleProfilerSignal(int signal, siginfo_t* info,
void* context) {
SB_UNREFERENCED_PARAMETER(info);
if (signal != SIGPROF) return;
sb_context_.ucontext = reinterpret_cast<ucontext_t*>(context);
// |Freeze| can return the context now.
sem_post(&freeze_semaphore_);
// Keep this thread frozen until |Thaw| is called.
sem_wait(&thaw_semaphore_);
}
} // namespace
SbThreadSamplerPrivate::SbThreadSamplerPrivate(SbThread thread)
: thread_(thread) {
SignalHandler::AddSampler();
}
SbThreadSamplerPrivate::~SbThreadSamplerPrivate() {
SignalHandler::RemoveSampler();
}
SbThreadContext SbThreadSamplerPrivate::Freeze() {
return SignalHandler::Freeze(this);
}
bool SbThreadSamplerPrivate::Thaw() { return SignalHandler::Thaw(this); }
#endif // SB_API_VERSION >= SB_THREAD_SAMPLER_VERSION