1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#define LOG_TAG "Trace"
18
19#include <cutils/properties.h>
20#include <utils/Log.h>
21#include <utils/Trace.h>
22#include <utils/misc.h>
23
24namespace android {
25
26volatile int32_t Tracer::sIsReady = 0;
27int Tracer::sTraceFD = -1;
28uint64_t Tracer::sEnabledTags = 0;
29Mutex Tracer::sMutex;
30
31void Tracer::changeCallback() {
32    Mutex::Autolock lock(sMutex);
33    if (sIsReady && sTraceFD >= 0) {
34        loadSystemProperty();
35    }
36}
37
38void Tracer::init() {
39    Mutex::Autolock lock(sMutex);
40
41    if (!sIsReady) {
42        add_sysprop_change_callback(changeCallback, 0);
43
44        const char* const traceFileName =
45                "/sys/kernel/debug/tracing/trace_marker";
46        sTraceFD = open(traceFileName, O_WRONLY);
47        if (sTraceFD == -1) {
48            ALOGE("error opening trace file: %s (%d)", strerror(errno), errno);
49            // sEnabledTags remains zero indicating that no tracing can occur
50        } else {
51            loadSystemProperty();
52        }
53
54        android_atomic_release_store(1, &sIsReady);
55    }
56}
57
58void Tracer::loadSystemProperty() {
59    char value[PROPERTY_VALUE_MAX];
60    property_get("debug.atrace.tags.enableflags", value, "0");
61    sEnabledTags = (strtoll(value, NULL, 0) & ATRACE_TAG_VALID_MASK)
62            | ATRACE_TAG_ALWAYS;
63}
64
65} // namespace andoid
66