1 files changed, 282 insertions, 0 deletions
diff --git a/libs/ui/FenceTime.cpp b/libs/ui/FenceTime.cpp
new file mode 100644
index 0000000000..c0245ebb89
--- /dev/null
+++ b/libs/ui/FenceTime.cpp
@@ -0,0 +1,282 @@
+/*
+* Copyright 2016 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 <ui/FenceTime.h>
+
+#include <cutils/compiler.h>  // For CC_[UN]LIKELY
+#include <inttypes.h>
+#include <stdlib.h>
+
+#include <memory>
+
+namespace android {
+
+// ============================================================================
+// FenceTime
+// ============================================================================
+
+const auto FenceTime::NO_FENCE = std::make_shared<FenceTime>(Fence::NO_FENCE);
+
+void* FenceTime::operator new(size_t byteCount) noexcept {
+    void *p = nullptr;
+    if (posix_memalign(&p, alignof(FenceTime), byteCount)) {
+        return nullptr;
+    }
+    return p;
+}
+
+void FenceTime::operator delete(void *p) {
+    free(p);
+}
+
+FenceTime::FenceTime(const sp<Fence>& fence)
+  : mState(((fence.get() != nullptr) && fence->isValid()) ?
+            State::VALID : State::INVALID),
+    mFence(fence),
+    mSignalTime(mState == State::INVALID ?
+            Fence::SIGNAL_TIME_INVALID : Fence::SIGNAL_TIME_PENDING) {
+}
+
+FenceTime::FenceTime(sp<Fence>&& fence)
+  : mState(((fence.get() != nullptr) && fence->isValid()) ?
+            State::VALID : State::INVALID),
+    mFence(std::move(fence)),
+    mSignalTime(mState == State::INVALID ?
+            Fence::SIGNAL_TIME_INVALID : Fence::SIGNAL_TIME_PENDING) {
+}
+
+FenceTime::FenceTime(nsecs_t signalTime)
+  : mState(Fence::isValidTimestamp(signalTime) ? State::VALID : State::INVALID),
+    mFence(nullptr),
+    mSignalTime(signalTime == Fence::SIGNAL_TIME_PENDING ?
+            Fence::SIGNAL_TIME_INVALID : signalTime) {
+}
+
+void FenceTime::applyTrustedSnapshot(const Snapshot& src) {
+    if (CC_UNLIKELY(src.state != Snapshot::State::SIGNAL_TIME)) {
+        // Applying Snapshot::State::FENCE, could change the valid state of the
+        // FenceTime, which is not allowed. Callers should create a new
+        // FenceTime from the snapshot instead.
+        ALOGE("FenceTime::applyTrustedSnapshot: Unexpected fence.");
+        return;
+    }
+
+    if (src.state == Snapshot::State::EMPTY) {
+        return;
+    }
+
+    nsecs_t signalTime = mSignalTime.load(std::memory_order_relaxed);
+    if (signalTime != Fence::SIGNAL_TIME_PENDING) {
+        // We should always get the same signalTime here that we did in
+        // getSignalTime(). This check races with getSignalTime(), but it is
+        // only a sanity check so that's okay.
+        if (CC_UNLIKELY(signalTime != src.signalTime)) {
+            ALOGE("FenceTime::applyTrustedSnapshot: signalTime mismatch. "
+                    "(%" PRId64 " (old) != %" PRId64 " (new))",
+                    signalTime, src.signalTime);
+        }
+        return;
+    }
+
+    std::lock_guard<std::mutex> lock(mMutex);
+    mFence.clear();
+    mSignalTime.store(src.signalTime, std::memory_order_relaxed);
+}
+
+bool FenceTime::isValid() const {
+    // We store the valid state in the constructors and return it here.
+    // This lets release code remember the valid state even after the
+    // underlying fence is destroyed.
+    return mState != State::INVALID;
+}
+
+nsecs_t FenceTime::getSignalTime() {
+    // See if we already have a cached value we can return.
+    nsecs_t signalTime = mSignalTime.load(std::memory_order_relaxed);
+    if (signalTime != Fence::SIGNAL_TIME_PENDING) {
+        return signalTime;
+    }
+
+    // Hold a reference to the fence on the stack in case the class'
+    // reference is removed by another thread. This prevents the
+    // fence from being destroyed until the end of this method, where
+    // we conveniently do not have the lock held.
+    sp<Fence> fence;
+    {
+        // With the lock acquired this time, see if we have the cached
+        // value or if we need to poll the fence.
+        std::lock_guard<std::mutex> lock(mMutex);
+        if (!mFence.get()) {
+            // Another thread set the signal time just before we added the
+            // reference to mFence.
+            return mSignalTime.load(std::memory_order_relaxed);
+        }
+        fence = mFence;
+    }
+
+    // Make the system call without the lock held.
+    signalTime = fence->getSignalTime();
+
+    // Make the signal time visible to everyone if it is no longer pending
+    // and remove the class' reference to the fence.
+    if (signalTime != Fence::SIGNAL_TIME_PENDING) {
+        std::lock_guard<std::mutex> lock(mMutex);
+        mFence.clear();
+        mSignalTime.store(signalTime, std::memory_order_relaxed);
+    }
+
+    return signalTime;
+}
+
+nsecs_t FenceTime::getCachedSignalTime() const {
+    // memory_order_acquire since we don't have a lock fallback path
+    // that will do an acquire.
+    return mSignalTime.load(std::memory_order_acquire);
+}
+
+FenceTime::Snapshot FenceTime::getSnapshot() const {
+    // Quick check without the lock.
+    nsecs_t signalTime = mSignalTime.load(std::memory_order_relaxed);
+    if (signalTime != Fence::SIGNAL_TIME_PENDING) {
+        return Snapshot(signalTime);
+    }
+
+    // Do the full check with the lock.
+    std::lock_guard<std::mutex> lock(mMutex);
+    signalTime = mSignalTime.load(std::memory_order_relaxed);
+    if (signalTime != Fence::SIGNAL_TIME_PENDING) {
+        return Snapshot(signalTime);
+    }
+    return Snapshot(mFence);
+}
+
+// ============================================================================
+// FenceTime::Snapshot
+// ============================================================================
+
+FenceTime::Snapshot::Snapshot(const sp<Fence>& srcFence)
+    : state(State::FENCE), fence(srcFence) {
+}
+
+FenceTime::Snapshot::Snapshot(nsecs_t srcSignalTime)
+    : state(State::SIGNAL_TIME), signalTime(srcSignalTime) {
+}
+
+size_t FenceTime::Snapshot::getFlattenedSize() const {
+    constexpr size_t min = sizeof(state);
+    switch (state) {
+        case State::EMPTY:
+            return min;
+        case State::FENCE:
+            return min + fence->getFlattenedSize();
+        case State::SIGNAL_TIME:
+            return min + sizeof(signalTime);
+    }
+    return 0;
+}
+
+size_t FenceTime::Snapshot::getFdCount() const {
+    return state == State::FENCE ? fence->getFdCount() : 0u;
+}
+
+status_t FenceTime::Snapshot::flatten(
+        void*& buffer, size_t& size, int*& fds, size_t& count) const {
+    if (size < getFlattenedSize()) {
+        return NO_MEMORY;
+    }
+
+    FlattenableUtils::write(buffer, size, state);
+    switch (state) {
+        case State::EMPTY:
+            return NO_ERROR;
+        case State::FENCE:
+            return fence->flatten(buffer, size, fds, count);
+        case State::SIGNAL_TIME:
+            FlattenableUtils::write(buffer, size, signalTime);
+            return NO_ERROR;
+    }
+
+    return NO_ERROR;
+}
+
+status_t FenceTime::Snapshot::unflatten(
+        void const*& buffer, size_t& size, int const*& fds, size_t& count) {
+    if (size < sizeof(state)) {
+        return NO_MEMORY;
+    }
+
+    FlattenableUtils::read(buffer, size, state);
+    switch (state) {
+        case State::EMPTY:
+            return NO_ERROR;
+        case State::FENCE:
+            fence = new Fence;
+            return fence->unflatten(buffer, size, fds, count);
+        case State::SIGNAL_TIME:
+            if (size < sizeof(signalTime)) {
+                return NO_MEMORY;
+            }
+            FlattenableUtils::read(buffer, size, signalTime);
+            return NO_ERROR;
+    }
+
+    return NO_ERROR;
+}
+
+// ============================================================================
+// FenceTimeline
+// ============================================================================
+void FenceTimeline::push(const std::shared_ptr<FenceTime>& fence) {
+    std::lock_guard<std::mutex> lock(mMutex);
+    while (mQueue.size() >= MAX_ENTRIES) {
+        // This is a sanity check to make sure the queue doesn't grow unbounded.
+        // MAX_ENTRIES should be big enough not to trigger this path.
+        // In case this path is taken though, users of FenceTime must make sure
+        // not to rely solely on FenceTimeline to get the final timestamp and
+        // should eventually call Fence::getSignalTime on their own.
+        std::shared_ptr<FenceTime> front = mQueue.front().lock();
+        if (front) {
+            // Make a last ditch effort to get the signalTime here since
+            // we are removing it from the timeline.
+            front->getSignalTime();
+        }
+        mQueue.pop();
+    }
+    mQueue.push(fence);
+}
+
+void FenceTimeline::updateSignalTimes() {
+    while (!mQueue.empty()) {
+        std::lock_guard<std::mutex> lock(mMutex);
+        std::shared_ptr<FenceTime> fence = mQueue.front().lock();
+        if (!fence) {
+            // The shared_ptr no longer exists and no one cares about the
+            // timestamp anymore.
+            mQueue.pop();
+            continue;
+        } else if (fence->getSignalTime() != Fence::SIGNAL_TIME_PENDING) {
+            // The fence has signaled and we've removed the sp<Fence> ref.
+            mQueue.pop();
+            continue;
+        } else {
+            // The fence didn't signal yet. Break since the later ones
+            // shouldn't have signaled either.
+            break;
+        }
+    }
+}
+
+} // namespace android