Trace.cpp revision 84ed8001d49a5b588fb78413655fe16fab5a3539 
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
23namespace android {
24
25volatile int32_t Tracer::sIsReady = 0;
26int Tracer::sTraceFD = -1;
27uint64_t Tracer::sEnabledTags = 0;
28Mutex Tracer::sMutex;
29
30void Tracer::init() {
31    Mutex::Autolock lock(sMutex);
32
33    if (!sIsReady) {
34        const char* const traceFileName =
35                "/sys/kernel/debug/tracing/trace_marker";
36        sTraceFD = open(traceFileName, O_WRONLY);
37        if (sTraceFD == -1) {
38            ALOGE("error opening trace file: %s (%d)", strerror(errno), errno);
39            // sEnabledTags remains zero indicating that no tracing can occur
40        } else {
41            char value[PROPERTY_VALUE_MAX];
42            property_get("atrace.tags.enableflags", value, "0");
43            sEnabledTags = (strtoll(value, NULL, 0) & ATRACE_TAG_VALID_MASK)
44                    | ATRACE_TAG_ALWAYS;
45        }
46
47        android_atomic_release_store(1, &sIsReady);
48    }
49}
50
51} // namespace andoid
52