libutils: add a system-wide tracing utility

/*

 * 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

 *

 *      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 ANDROID_TRACE_H

#define ANDROID_TRACE_H

#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.

#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_LAST     (1<<1)

#define ATRACE_TAG_INVALID (~((ATRACE_TAG_LAST - 1) | ATRACE_TAG_LAST))

#ifndef ATRACE_TAG

#define ATRACE_TAG ATRACE_TAG_NEVER

#elif ATRACE_TAG > ATRACE_TAG_LAST

#error ATRACE_TAG must be defined to be one of the tags defined in utils/Trace.h

#endif

// 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)

namespace android {

class Tracer {

public:

    static inline void traceCounter(uint64_t tag, const char* name,

            int32_t value) {

        if (!android_atomic_acquire_load(&sIsReady)) {

            init();

        }

        int traceFD = sTraceFD;

        if (CC_UNLIKELY(tagEnabled(tag) && traceFD != -1)) {

            char buf[1024];

            snprintf(buf, 1024, "C|%d|%s|%d", getpid(), name, value);

            write(traceFD, buf, strlen(buf));

        }

    }

    static inline void traceBegin(uint64_t tag, const char* name) {

        if (CC_UNLIKELY(!android_atomic_acquire_load(&sIsReady))) {

            init();

        }

        int traceFD = sTraceFD;

        if (CC_UNLIKELY(tagEnabled(tag) && (traceFD != -1))) {

            char buf[1024];

            size_t len = snprintf(buf, 1024, "B|%d|%s", getpid(), name);

            write(traceFD, buf, len);

        }

    }

   static inline void traceEnd(uint64_t tag) {

        if (CC_UNLIKELY(!android_atomic_acquire_load(&sIsReady))) {

            init();

        }

        int traceFD = sTraceFD;

        if (CC_UNLIKELY(tagEnabled(tag) && (traceFD != -1))) {

            char buf = 'E';

            write(traceFD, &buf, 1);

        }

    }

private:

    static inline bool tagEnabled(uint64_t tag) {

        return !(tag & ATRACE_TAG_INVALID) && (tag & sEnabledTags);

    }

    // 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();

    // 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.

    static uint64_t sEnabledTags;

    // sMutex is used to protect the execution of init().

    static Mutex sMutex;

};

class ScopedTrace {

public:

    inline ScopedTrace(uint64_t tag, const char* name) :

            mTag(tag) {

        Tracer::traceBegin(mTag, name);

    }

    inline ~ScopedTrace() {

        Tracer::traceEnd(mTag);

    }

private:

    uint64_t mTag;

};

}; // namespace android

#endif // ANDROID_TRACE_H

# we have the common sources, plus some device-specific stuff

LOCAL_SRC_FILES:= \

	$(commonSources) \

	Looper.cpp

	Looper.cpp \

	Trace.cpp

ifeq ($(TARGET_OS),linux)

LOCAL_LDLIBS += -lrt -ldl

/*

 * 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

 *

 *      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 <cutils/properties.h>

#include <utils/Log.h>

#include <utils/Trace.h>

namespace android {

volatile int32_t Tracer::sIsReady = 0;

int Tracer::sTraceFD = -1;

uint64_t Tracer::sEnabledTags = 0;

Mutex Tracer::sMutex;

void Tracer::init() {

    Mutex::Autolock lock(sMutex);

    if (!sIsReady) {

        const char* const traceFileName =

                "/sys/kernel/debug/tracing/trace_marker";

        sTraceFD = open(traceFileName, O_WRONLY);

        if (sTraceFD == -1) {

            ALOGE("error opening trace file: %s (%d)", strerror(errno), errno);

        } else {

            char value[PROPERTY_VALUE_MAX];

            property_get("atrace.tags.enableflags", value, "0");

            sEnabledTags = strtoll(value, NULL, 0) | ATRACE_TAG_ALWAYS;

        }

        android_atomic_release_store(1, &sIsReady);

    }

}

} // namespace andoid