1 /*
2 * Copyright (C) 2018 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 #include "perfetto/base/build_config.h"
18 #if !PERFETTO_BUILDFLAG(PERFETTO_OS_WIN)
19
20 #include <stdint.h>
21 #include <unistd.h>
22
23 #include "perfetto/base/logging.h"
24 #include "perfetto/ext/base/event_fd.h"
25 #include "perfetto/ext/base/pipe.h"
26 #include "perfetto/ext/base/utils.h"
27
28 #if PERFETTO_USE_EVENTFD()
29 #include <sys/eventfd.h>
30 #endif
31
32 namespace perfetto {
33 namespace base {
34
EventFd()35 EventFd::EventFd() {
36 #if PERFETTO_USE_EVENTFD()
37 fd_.reset(eventfd(/* start value */ 0, EFD_CLOEXEC | EFD_NONBLOCK));
38 PERFETTO_CHECK(fd_);
39 #else
40 // Make the pipe non-blocking so that we never block the waking thread (either
41 // the main thread or another one) when scheduling a wake-up.
42 Pipe pipe = Pipe::Create(Pipe::kBothNonBlock);
43 fd_ = std::move(pipe.rd);
44 write_fd_ = std::move(pipe.wr);
45 #endif // !PERFETTO_USE_EVENTFD()
46 }
47
48 EventFd::~EventFd() = default;
49
Notify()50 void EventFd::Notify() {
51 const uint64_t value = 1;
52
53 #if PERFETTO_USE_EVENTFD()
54 ssize_t ret = write(fd_.get(), &value, sizeof(value));
55 #else
56 ssize_t ret = write(write_fd_.get(), &value, sizeof(uint8_t));
57 #endif
58
59 if (ret <= 0 && errno != EAGAIN) {
60 PERFETTO_DFATAL("write()");
61 }
62 }
63
Clear()64 void EventFd::Clear() {
65 #if PERFETTO_USE_EVENTFD()
66 uint64_t value;
67 ssize_t ret = read(fd_.get(), &value, sizeof(value));
68 #else
69 // Drain the byte(s) written to the wake-up pipe. We can potentially read
70 // more than one byte if several wake-ups have been scheduled.
71 char buffer[16];
72 ssize_t ret = read(fd_.get(), &buffer[0], sizeof(buffer));
73 #endif
74 if (ret <= 0 && errno != EAGAIN)
75 PERFETTO_DPLOG("read()");
76 }
77
78 } // namespace base
79 } // namespace perfetto
80
81 #endif // !PERFETTO_BUILDFLAG(PERFETTO_OS_WIN)
82