SF: add VSyncDispatch timing objects

Add epoll and timerfd dispatch of events.

Fixes: 140303478
Bug: 140301853
Test: 3 new VSyncDispatchRealtimeTest

Change-Id: Ibc9bbaacfe3774247fb3d059dab3769bb17f3194
diff --git a/services/surfaceflinger/Scheduler/Timer.cpp b/services/surfaceflinger/Scheduler/Timer.cpp
new file mode 100644
index 0000000..2394ed2
--- /dev/null
+++ b/services/surfaceflinger/Scheduler/Timer.cpp
@@ -0,0 +1,181 @@
+/*
+ * Copyright 2019 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.
+ */
+
+#undef LOG_TAG
+#define LOG_TAG "SchedulerTimer"
+#define ATRACE_TAG ATRACE_TAG_GRAPHICS
+#include <log/log.h>
+#include <sys/epoll.h>
+#include <sys/timerfd.h>
+#include <sys/unistd.h>
+#include <utils/Trace.h>
+#include <chrono>
+#include <cstdint>
+
+#include "Timer.h"
+
+namespace android::scheduler {
+
+static constexpr size_t kReadPipe = 0;
+static constexpr size_t kWritePipe = 1;
+
+template <class T, size_t N>
+constexpr size_t arrayLen(T (&)[N]) {
+    return N;
+}
+
+Timer::Timer()
+      : mTimerFd(timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)),
+        mEpollFd(epoll_create1(EPOLL_CLOEXEC)) {
+    if (pipe2(mPipes.data(), O_CLOEXEC | O_NONBLOCK)) {
+        ALOGE("could not create TimerDispatch mPipes");
+    };
+
+    mDispatchThread = std::thread(std::bind(&Timer::dispatch, this));
+}
+
+Timer::~Timer() {
+    endDispatch();
+    mDispatchThread.join();
+
+    close(mPipes[kWritePipe]);
+    close(mPipes[kReadPipe]);
+    close(mEpollFd);
+    close(mTimerFd);
+}
+
+void Timer::endDispatch() {
+    static constexpr unsigned char end = 'e';
+    write(mPipes[kWritePipe], &end, sizeof(end));
+}
+
+nsecs_t Timer::now() const {
+    return systemTime(SYSTEM_TIME_MONOTONIC);
+}
+
+constexpr char const* timerTraceTag = "AlarmInNs";
+void Timer::alarmIn(std::function<void()> const& cb, nsecs_t fireIn) {
+    std::lock_guard<decltype(mMutex)> lk(mMutex);
+    ATRACE_INT64(timerTraceTag, fireIn);
+
+    using namespace std::literals;
+    static constexpr int ns_per_s =
+            std::chrono::duration_cast<std::chrono::nanoseconds>(1s).count();
+
+    mCallback = cb;
+
+    struct itimerspec old_timer;
+    struct itimerspec new_timer {
+        .it_interval = {.tv_sec = 0, .tv_nsec = 0},
+        .it_value = {.tv_sec = static_cast<long>(fireIn / ns_per_s),
+                     .tv_nsec = static_cast<long>(fireIn % ns_per_s)},
+    };
+
+    if (timerfd_settime(mTimerFd, 0, &new_timer, &old_timer)) {
+        ALOGW("Failed to set timerfd");
+    }
+}
+
+void Timer::alarmCancel() {
+    std::lock_guard<decltype(mMutex)> lk(mMutex);
+    ATRACE_INT64(timerTraceTag, 0);
+
+    struct itimerspec old_timer;
+    struct itimerspec new_timer {
+        .it_interval = {.tv_sec = 0, .tv_nsec = 0},
+        .it_value = {
+                .tv_sec = 0,
+                .tv_nsec = 0,
+        },
+    };
+
+    if (timerfd_settime(mTimerFd, 0, &new_timer, &old_timer)) {
+        ALOGW("Failed to disarm timerfd");
+    }
+}
+
+void Timer::dispatch() {
+    struct sched_param param = {0};
+    param.sched_priority = 2;
+    if (pthread_setschedparam(pthread_self(), SCHED_FIFO, &param) != 0) {
+        ALOGW("Failed to set SCHED_FIFO on dispatch thread");
+    }
+
+    if (pthread_setname_np(pthread_self(), "TimerDispatch")) {
+        ALOGW("Failed to set thread name on dispatch thread");
+    }
+
+    enum DispatchType : uint32_t { TIMER, TERMINATE, MAX_DISPATCH_TYPE };
+    epoll_event timerEvent;
+    timerEvent.events = EPOLLIN;
+    timerEvent.data.u32 = DispatchType::TIMER;
+    if (epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mTimerFd, &timerEvent) == -1) {
+        ALOGE("Error adding timer fd to epoll dispatch loop");
+        return;
+    }
+
+    epoll_event terminateEvent;
+    terminateEvent.events = EPOLLIN;
+    terminateEvent.data.u32 = DispatchType::TERMINATE;
+    if (epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mPipes[kReadPipe], &terminateEvent) == -1) {
+        ALOGE("Error adding control fd to dispatch loop");
+        return;
+    }
+
+    uint64_t iteration = 0;
+    char const traceNamePrefix[] = "TimerIteration #";
+    static constexpr size_t max64print = std::numeric_limits<decltype(iteration)>::digits10;
+    static constexpr size_t maxlen = arrayLen(traceNamePrefix) + max64print;
+    std::array<char, maxlen> str_buffer;
+    auto timing = true;
+    while (timing) {
+        epoll_event events[DispatchType::MAX_DISPATCH_TYPE];
+        int nfds = epoll_wait(mEpollFd, events, DispatchType::MAX_DISPATCH_TYPE, -1);
+
+        if (ATRACE_ENABLED()) {
+            snprintf(str_buffer.data(), str_buffer.size(), "%s%" PRIu64, traceNamePrefix,
+                     iteration++);
+            ATRACE_NAME(str_buffer.data());
+        }
+
+        if (nfds == -1) {
+            if (errno != EINTR) {
+                timing = false;
+                continue;
+            }
+        }
+
+        for (auto i = 0; i < nfds; i++) {
+            if (events[i].data.u32 == DispatchType::TIMER) {
+                static uint64_t mIgnored = 0;
+                read(mTimerFd, &mIgnored, sizeof(mIgnored));
+                std::function<void()> cb;
+                {
+                    std::lock_guard<decltype(mMutex)> lk(mMutex);
+                    cb = mCallback;
+                }
+                if (cb) {
+                    cb();
+                }
+            }
+            if (events[i].data.u32 == DispatchType::TERMINATE) {
+                timing = false;
+            }
+        }
+    }
+}
+
+} // namespace android::scheduler