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* Copyright (C) 2012 The Android Open Source Project
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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#ifndef ANDROID_TRACE_H
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#define ANDROID_TRACE_H
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#include <sys/types.h>
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#include <cutils/compiler.h>
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#include <utils/threads.h>
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// The ATRACE_TAG macro can be defined before including this header to trace
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// using one of the tags defined below. It must be defined to one of the
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// following ATRACE_TAG_* macros. The trace tag is used to filter tracing in
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// userland to avoid some of the runtime cost of tracing when it is not desired.
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// Defining ATRACE_TAG to be ATRACE_TAG_ALWAYS will result in the tracing always
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// being enabled - this should ONLY be done for debug code, as userland tracing
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// has a performance cost even when the trace is not being recorded. Defining
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// ATRACE_TAG to be ATRACE_TAG_NEVER or leaving ATRACE_TAG undefined will result
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// in the tracing always being disabled.
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// These tags must be kept in sync with frameworks/base/core/java/android/os/Trace.java.
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#define ATRACE_TAG_NEVER 0 // The "never" tag is never enabled.
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#define ATRACE_TAG_ALWAYS (1<<0) // The "always" tag is always enabled.
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#define ATRACE_TAG_GRAPHICS (1<<1)
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#define ATRACE_TAG_INPUT (1<<2)
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#define ATRACE_TAG_VIEW (1<<3)
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#define ATRACE_TAG_WEBVIEW (1<<4)
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#define ATRACE_TAG_WINDOW_MANAGER (1<<5)
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#define ATRACE_TAG_ACTIVITY_MANAGER (1<<6)
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#define ATRACE_TAG_SYNC_MANAGER (1<<7)
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#define ATRACE_TAG_AUDIO (1<<8)
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#define ATRACE_TAG_VIDEO (1<<9)
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#define ATRACE_TAG_LAST ATRACE_TAG_VIDEO
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#define ATRACE_TAG_VALID_MASK ((ATRACE_TAG_LAST - 1) | ATRACE_TAG_LAST)
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#define ATRACE_TAG ATRACE_TAG_NEVER
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#elif ATRACE_TAG > ATRACE_TAG_LAST
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#error ATRACE_TAG must be defined to be one of the tags defined in utils/Trace.h
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// ATRACE_CALL traces the beginning and end of the current function. To trace
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// the correct start and end times this macro should be the first line of the
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#define ATRACE_CALL() android::ScopedTrace ___tracer(ATRACE_TAG, __FUNCTION__)
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// ATRACE_INT traces a named integer value. This can be used to track how the
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// value changes over time in a trace.
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#define ATRACE_INT(name, value) android::Tracer::traceCounter(ATRACE_TAG, name, value)
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// ATRACE_ENABLED returns true if the trace tag is enabled. It can be used as a
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// guard condition around more expensive trace calculations.
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#define ATRACE_ENABLED() android::Tracer::isTagEnabled(ATRACE_TAG)
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static uint64_t getEnabledTags() {
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static inline bool isTagEnabled(uint64_t tag) {
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return sEnabledTags & tag;
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static inline void traceCounter(uint64_t tag, const char* name,
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if (CC_UNLIKELY(isTagEnabled(tag))) {
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snprintf(buf, 1024, "C|%d|%s|%d", getpid(), name, value);
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write(sTraceFD, buf, strlen(buf));
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static inline void traceBegin(uint64_t tag, const char* name) {
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if (CC_UNLIKELY(isTagEnabled(tag))) {
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size_t len = snprintf(buf, 1024, "B|%d|%s", getpid(), name);
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write(sTraceFD, buf, len);
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static inline void traceEnd(uint64_t tag) {
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if (CC_UNLIKELY(isTagEnabled(tag))) {
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write(sTraceFD, &buf, 1);
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static inline void initIfNeeded() {
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if (!android_atomic_acquire_load(&sIsReady)) {
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static void changeCallback();
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// init opens the trace marker file for writing and reads the
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// atrace.tags.enableflags system property. It does this only the first
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// time it is run, using sMutex for synchronization.
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// retrieve the current value of the system property.
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static void loadSystemProperty();
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// sIsReady is a boolean value indicating whether a call to init() has
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// completed in this process. It is initialized to 0 and set to 1 when the
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// first init() call completes. It is set to 1 even if a failure occurred
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// in init (e.g. the trace marker file couldn't be opened).
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// This should be checked by all tracing functions using an atomic acquire
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// load operation before calling init(). This check avoids the need to lock
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// a mutex each time a trace function gets called.
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static volatile int32_t sIsReady;
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// sTraceFD is the file descriptor used to write to the kernel's trace
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// buffer. It is initialized to -1 and set to an open file descriptor in
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// init() while a lock on sMutex is held.
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// This should only be used by a trace function after init() has
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// successfully completed.
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// sEnabledTags is the set of tag bits for which tracing is currently
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// enabled. It is initialized to 0 and set based on the
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// atrace.tags.enableflags system property in init() while a lock on sMutex
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// This should only be used by a trace function after init() has
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// successfully completed.
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// This value is only ever non-zero when tracing is initialized and sTraceFD is not -1.
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static uint64_t sEnabledTags;
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// sMutex is used to protect the execution of init().
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inline ScopedTrace(uint64_t tag, const char* name) :
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Tracer::traceBegin(mTag, name);
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inline ~ScopedTrace() {
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Tracer::traceEnd(mTag);
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}; // namespace android
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#endif // ANDROID_TRACE_H