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* Copyright (C) 2012 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <cutils/compiler.h>
#include <utils/threads.h>
// The ATRACE_TAG macro can be defined before including this header to trace
// using one of the tags defined below. It must be defined to one of the
// following ATRACE_TAG_* macros. The trace tag is used to filter tracing in
// userland to avoid some of the runtime cost of tracing when it is not desired.
// Defining ATRACE_TAG to be ATRACE_TAG_ALWAYS will result in the tracing always
// being enabled - this should ONLY be done for debug code, as userland tracing
// has a performance cost even when the trace is not being recorded. Defining
// ATRACE_TAG to be ATRACE_TAG_NEVER or leaving ATRACE_TAG undefined will result
// in the tracing always being disabled.
// These tags must be kept in sync with frameworks/base/core/java/android/os/
#define ATRACE_TAG_NEVER 0 // The "never" tag is never enabled.
#define ATRACE_TAG_ALWAYS (1<<0) // The "always" tag is always enabled.
#define ATRACE_TAG_GRAPHICS (1<<1)
#define ATRACE_TAG_INPUT (1<<2)
#define ATRACE_TAG_VIEW (1<<3)
#define ATRACE_TAG_WEBVIEW (1<<4)
#define ATRACE_TAG_AUDIO (1<<8)
#define ATRACE_TAG_VIDEO (1<<9)
#ifndef ATRACE_TAG
#error ATRACE_TAG must be defined to be one of the tags defined in utils/Trace.h
// ATRACE_CALL traces the beginning and end of the current function. To trace
// the correct start and end times this macro should be the first line of the
// function body.
#define ATRACE_CALL() android::ScopedTrace ___tracer(ATRACE_TAG, __FUNCTION__)
// ATRACE_INT traces a named integer value. This can be used to track how the
// value changes over time in a trace.
#define ATRACE_INT(name, value) android::Tracer::traceCounter(ATRACE_TAG, name, value)
// ATRACE_ENABLED returns true if the trace tag is enabled. It can be used as a
// guard condition around more expensive trace calculations.
#define ATRACE_ENABLED() android::Tracer::isTagEnabled(ATRACE_TAG)
namespace android {
class Tracer {
static uint64_t getEnabledTags() {
return sEnabledTags;
static inline bool isTagEnabled(uint64_t tag) {
return sEnabledTags & tag;
static inline void traceCounter(uint64_t tag, const char* name,
int32_t value) {
if (CC_UNLIKELY(isTagEnabled(tag))) {
char buf[1024];
snprintf(buf, 1024, "C|%d|%s|%d", getpid(), name, value);
write(sTraceFD, buf, strlen(buf));
static inline void traceBegin(uint64_t tag, const char* name) {
if (CC_UNLIKELY(isTagEnabled(tag))) {
char buf[1024];
size_t len = snprintf(buf, 1024, "B|%d|%s", getpid(), name);
write(sTraceFD, buf, len);
static inline void traceEnd(uint64_t tag) {
if (CC_UNLIKELY(isTagEnabled(tag))) {
char buf = 'E';
write(sTraceFD, &buf, 1);
static inline void initIfNeeded() {
if (!android_atomic_acquire_load(&sIsReady)) {
static void changeCallback();
// init opens the trace marker file for writing and reads the
// atrace.tags.enableflags system property. It does this only the first
// time it is run, using sMutex for synchronization.
static void init();
// retrieve the current value of the system property.
static void loadSystemProperty();
// sIsReady is a boolean value indicating whether a call to init() has
// completed in this process. It is initialized to 0 and set to 1 when the
// first init() call completes. It is set to 1 even if a failure occurred
// in init (e.g. the trace marker file couldn't be opened).
// This should be checked by all tracing functions using an atomic acquire
// load operation before calling init(). This check avoids the need to lock
// a mutex each time a trace function gets called.
static volatile int32_t sIsReady;
// sTraceFD is the file descriptor used to write to the kernel's trace
// buffer. It is initialized to -1 and set to an open file descriptor in
// init() while a lock on sMutex is held.
// This should only be used by a trace function after init() has
// successfully completed.
static int sTraceFD;
// sEnabledTags is the set of tag bits for which tracing is currently
// enabled. It is initialized to 0 and set based on the
// atrace.tags.enableflags system property in init() while a lock on sMutex
// is held.
// This should only be used by a trace function after init() has
// successfully completed.
// This value is only ever non-zero when tracing is initialized and sTraceFD is not -1.
static uint64_t sEnabledTags;
// sMutex is used to protect the execution of init().
static Mutex sMutex;
class ScopedTrace {
inline ScopedTrace(uint64_t tag, const char* name) :
mTag(tag) {
Tracer::traceBegin(mTag, name);
inline ~ScopedTrace() {
uint64_t mTag;
}; // namespace android