chromium/third_party/perfetto/src/trace_processor/types/task_state.h

/*
 * 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.
 */

#ifndef SRC_TRACE_PROCESSOR_TYPES_TASK_STATE_H_
#define SRC_TRACE_PROCESSOR_TYPES_TASK_STATE_H_

#include <stdint.h>
#include <array>
#include <optional>

#include "src/trace_processor/types/version_number.h"

namespace perfetto {
namespace trace_processor {
namespace ftrace_utils {

// Linux kernel scheduling events (sched_switch) contain a bitmask of the
// switched-out task's state (prev_state). Perfetto doesn't record the event
// format string during tracing, the trace contains only the raw bitmask as an
// integer. Certain kernel versions made backwards incompatible changes to the
// bitmask's raw representation, so this class guesses how to decode the flags
// based on the kernel's major+minor version as recorded in the trace. Note:
// this means we can be wrong if patch backports change the flags, or the
// kernel diverged from upstream. But this has worked well enough in practice
// so far.
//
// There are three specific kernel version intervals we handle:
// * [4.14, ...)
// * [4.8, 4.14)
// * (..., 4.8), where we assume the 4.4 bitmask
//
// (Therefore kernels before 4.2 most likely have incorrect preemption flag
// parsing.)
//
// For 4.14, we assume that the kernel has a backport of the bugfix
// https://github.com/torvalds/linux/commit/3f5fe9fe ("sched/debug: Fix task
// state recording/printout"). In other words, traces collected on unpatched
// 4.14 kernels will have incorrect flags decoded.
class TaskState { … };

}  // namespace ftrace_utils
}  // namespace trace_processor
}  // namespace perfetto

#endif  // SRC_TRACE_PROCESSOR_TYPES_TASK_STATE_H_