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/*
* Copyright (C) 2019 The Android Open Source Project
*
* 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 "perfetto/ext/tracing/core/startup_trace_writer_registry.h"
#include <algorithm>
#include <cmath>
#include <functional>
#include "perfetto/base/logging.h"
#include "perfetto/base/task_runner.h"
#include "perfetto/ext/tracing/core/startup_trace_writer.h"
#include "src/tracing/core/shared_memory_arbiter_impl.h"
using ChunkHeader = perfetto::SharedMemoryABI::ChunkHeader;
namespace perfetto {
StartupTraceWriterRegistryHandle::StartupTraceWriterRegistryHandle(
StartupTraceWriterRegistry* registry)
: registry_(registry) {}
void StartupTraceWriterRegistryHandle::ReturnWriterToRegistry(
std::unique_ptr<StartupTraceWriter> writer) {
std::lock_guard<std::mutex> lock(lock_);
if (registry_)
registry_->ReturnTraceWriter(std::move(writer));
}
void StartupTraceWriterRegistryHandle::OnRegistryDestroyed() {
std::lock_guard<std::mutex> lock(lock_);
registry_ = nullptr;
}
StartupTraceWriterRegistry::StartupTraceWriterRegistry()
: handle_(std::make_shared<StartupTraceWriterRegistryHandle>(this)) {}
StartupTraceWriterRegistry::~StartupTraceWriterRegistry() {
handle_->OnRegistryDestroyed();
}
// static
constexpr size_t StartupTraceWriterRegistry::kDefaultMaxBufferSizeBytes;
std::unique_ptr<StartupTraceWriter>
StartupTraceWriterRegistry::CreateUnboundTraceWriter(
BufferExhaustedPolicy buffer_exhausted_policy,
size_t max_buffer_size_bytes) {
std::lock_guard<std::mutex> lock(lock_);
PERFETTO_DCHECK(!arbiter_); // Should only be called while unbound.
std::unique_ptr<StartupTraceWriter> writer(new StartupTraceWriter(
handle_, buffer_exhausted_policy, max_buffer_size_bytes));
unbound_writers_.push_back(writer.get());
return writer;
}
void StartupTraceWriterRegistry::ReturnTraceWriter(
std::unique_ptr<StartupTraceWriter> trace_writer) {
std::lock_guard<std::mutex> lock(lock_);
PERFETTO_DCHECK(!trace_writer->write_in_progress_);
auto it = std::find(unbound_writers_.begin(), unbound_writers_.end(),
trace_writer.get());
// If the registry is already bound, but the writer wasn't, bind it now.
if (arbiter_) {
if (it == unbound_writers_.end()) {
// Nothing to do, the writer was already bound.
return;
}
// This should succeed since nobody can write to this writer concurrently.
bool success = trace_writer->BindToArbiter(arbiter_, target_buffer_,
chunks_per_batch_);
PERFETTO_DCHECK(success);
unbound_writers_.erase(it);
OnUnboundWritersRemovedLocked();
return;
}
// If the registry was not bound yet, keep the writer alive until it is.
PERFETTO_DCHECK(it != unbound_writers_.end());
unbound_writers_.erase(it);
unbound_owned_writers_.push_back(std::move(trace_writer));
}
void StartupTraceWriterRegistry::BindToArbiter(
SharedMemoryArbiterImpl* arbiter,
BufferID target_buffer,
base::TaskRunner* task_runner,
std::function<void(StartupTraceWriterRegistry*)> on_bound_callback) {
std::vector<std::unique_ptr<StartupTraceWriter>> unbound_owned_writers;
{
std::lock_guard<std::mutex> lock(lock_);
PERFETTO_DCHECK(!arbiter_);
arbiter_ = arbiter;
target_buffer_ = target_buffer;
task_runner_ = task_runner;
// Attempt to use at most half the SMB for binding of StartupTraceWriters at
// the same time. In the worst case, all writers are binding at the same
// time, so divide it up between them.
//
// TODO(eseckler): This assumes that there's only a single registry at the
// same time. SharedMemoryArbiterImpl should advise us how much of the SMB
// we're allowed to use in the first place.
size_t num_writers =
unbound_owned_writers_.size() + unbound_writers_.size();
if (num_writers) {
chunks_per_batch_ = arbiter_->num_pages() / 2 / num_writers;
} else {
chunks_per_batch_ = arbiter_->num_pages() / 2;
}
// We should use at least one chunk per batch.
chunks_per_batch_ = std::max(chunks_per_batch_, static_cast<size_t>(1u));
// Weakptrs should be valid on |task_runner|. For this, the factory needs to
// be created on |task_runner|, i.e. BindToArbiter must be called on
// |task_runner|.
PERFETTO_DCHECK(task_runner_->RunsTasksOnCurrentThread());
weak_ptr_factory_.reset(
new base::WeakPtrFactory<StartupTraceWriterRegistry>(this));
on_bound_callback_ = std::move(on_bound_callback);
// We can't destroy the writers while holding |lock_|, so we swap them out
// here instead. After we are bound, no more writers can be added to the
// list.
unbound_owned_writers.swap(unbound_owned_writers_);
}
// Bind and destroy the owned writers.
for (const auto& writer : unbound_owned_writers) {
// This should succeed since nobody can write to these writers concurrently.
bool success =
writer->BindToArbiter(arbiter_, target_buffer_, chunks_per_batch_);
PERFETTO_DCHECK(success);
}
unbound_owned_writers.clear();
TryBindWriters();
}
void StartupTraceWriterRegistry::TryBindWriters() {
std::lock_guard<std::mutex> lock(lock_);
for (auto it = unbound_writers_.begin(); it != unbound_writers_.end();) {
if ((*it)->BindToArbiter(arbiter_, target_buffer_, chunks_per_batch_)) {
it = unbound_writers_.erase(it);
} else {
break;
}
}
if (!unbound_writers_.empty()) {
auto weak_this = weak_ptr_factory_->GetWeakPtr();
task_runner_->PostTask([weak_this] {
if (weak_this)
weak_this->TryBindWriters();
});
}
OnUnboundWritersRemovedLocked();
}
void StartupTraceWriterRegistry::OnUnboundWritersRemovedLocked() {
if (!unbound_writers_.empty() || !task_runner_ || !on_bound_callback_)
return;
PERFETTO_DCHECK(weak_ptr_factory_);
auto weak_this = weak_ptr_factory_->GetWeakPtr();
// Run callback in PostTask() since the callback may delete |this| and thus
// might otherwise cause a deadlock.
auto callback = on_bound_callback_;
on_bound_callback_ = nullptr;
task_runner_->PostTask([weak_this, callback]() {
if (!weak_this)
return;
// Note: callback may delete |this|.
callback(weak_this.get());
});
}
} // namespace perfetto
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