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/*
* Copyright (C) 2018 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/base/metatrace.h"
#include "perfetto/base/compiler.h"
#include "perfetto/base/task_runner.h"
#include "perfetto/base/time.h"
#include "perfetto/ext/base/file_utils.h"
#include "perfetto/ext/base/thread_annotations.h"
namespace perfetto {
namespace metatrace {
std::atomic<uint32_t> g_enabled_tags{0};
std::atomic<uint64_t> g_enabled_timestamp{0};
// static members
constexpr size_t RingBuffer::kCapacity;
std::array<Record, RingBuffer::kCapacity> RingBuffer::records_;
std::atomic<bool> RingBuffer::read_task_queued_;
std::atomic<uint64_t> RingBuffer::wr_index_;
std::atomic<uint64_t> RingBuffer::rd_index_;
std::atomic<bool> RingBuffer::has_overruns_;
Record RingBuffer::bankruptcy_record_;
constexpr uint16_t Record::kTypeMask;
constexpr uint16_t Record::kTypeCounter;
constexpr uint16_t Record::kTypeEvent;
namespace {
// std::function<> is not trivially de/constructible. This struct wraps it in a
// heap-allocated struct to avoid static initializers.
struct Delegate {
static Delegate* GetInstance() {
static Delegate* instance = new Delegate();
return instance;
}
base::TaskRunner* task_runner = nullptr;
std::function<void()> read_task;
};
} // namespace
bool Enable(std::function<void()> read_task,
base::TaskRunner* task_runner,
uint32_t tags) {
PERFETTO_DCHECK(read_task);
PERFETTO_DCHECK(task_runner->RunsTasksOnCurrentThread());
if (g_enabled_tags.load(std::memory_order_acquire))
return false;
Delegate* dg = Delegate::GetInstance();
dg->task_runner = task_runner;
dg->read_task = std::move(read_task);
RingBuffer::Reset();
g_enabled_timestamp.store(TraceTimeNowNs(), std::memory_order_relaxed);
g_enabled_tags.store(tags, std::memory_order_release);
return true;
}
void Disable() {
g_enabled_tags.store(0, std::memory_order_release);
Delegate* dg = Delegate::GetInstance();
PERFETTO_DCHECK(!dg->task_runner ||
dg->task_runner->RunsTasksOnCurrentThread());
dg->task_runner = nullptr;
dg->read_task = nullptr;
}
// static
void RingBuffer::Reset() {
bankruptcy_record_.clear();
for (Record& record : records_)
record.clear();
wr_index_ = 0;
rd_index_ = 0;
has_overruns_ = false;
read_task_queued_ = false;
}
// static
Record* RingBuffer::AppendNewRecord() {
auto wr_index = wr_index_.fetch_add(1, std::memory_order_acq_rel);
// rd_index can only monotonically increase, we don't care if we read an
// older value, we'll just hit the slow-path a bit earlier if it happens.
auto rd_index = rd_index_.load(std::memory_order_relaxed);
PERFETTO_DCHECK(wr_index >= rd_index);
auto size = wr_index - rd_index;
if (PERFETTO_LIKELY(size < kCapacity / 2))
return At(wr_index);
// Slow-path: Enqueue the read task and handle overruns.
bool expected = false;
if (RingBuffer::read_task_queued_.compare_exchange_strong(expected, true)) {
Delegate* dg = Delegate::GetInstance();
if (dg->task_runner) {
dg->task_runner->PostTask([] {
// Meta-tracing might have been disabled in the meantime.
auto read_task = Delegate::GetInstance()->read_task;
if (read_task)
read_task();
RingBuffer::read_task_queued_ = false;
});
}
}
if (PERFETTO_LIKELY(size < kCapacity))
return At(wr_index);
has_overruns_.store(true, std::memory_order_release);
wr_index_.fetch_sub(1, std::memory_order_acq_rel);
// In the case of overflows, threads will race writing on the same memory
// location and TSan will rightly complain. This is fine though because nobody
// will read the bankruptcy record and it's designed to contain garbage.
PERFETTO_ANNOTATE_BENIGN_RACE_SIZED(&bankruptcy_record_, sizeof(Record),
"nothing reads bankruptcy_record_")
return &bankruptcy_record_;
}
// static
bool RingBuffer::IsOnValidTaskRunner() {
auto* task_runner = Delegate::GetInstance()->task_runner;
return task_runner && task_runner->RunsTasksOnCurrentThread();
}
} // namespace metatrace
} // namespace perfetto