Add Fence helpers: Time, Timeline, Snapshot (221de2a3) · Commits · e / os / platform_frameworks_native

include/ui/Fence.h

+7 −2

Original line number	Diff line number	Diff line
		@@ -42,6 +42,11 @@ class Fence
		{
		public:
		static const sp<Fence> NO_FENCE;
		static constexpr nsecs_t SIGNAL_TIME_PENDING = INT64_MAX;
		static constexpr nsecs_t SIGNAL_TIME_INVALID = -1;
		static inline bool isValidTimestamp(nsecs_t time) {
		return time >= 0 && time < INT64_MAX;
		}

		// TIMEOUT_NEVER may be passed to the wait method to indicate that it
		// should wait indefinitely for the fence to signal.
		@@ -94,8 +99,8 @@ public:

		// getSignalTime returns the system monotonic clock time at which the
		// fence transitioned to the signaled state. If the fence is not signaled
		// then INT64_MAX is returned. If the fence is invalid or if an error
		// occurs then -1 is returned.
		// then SIGNAL_TIME_PENDING is returned. If the fence is invalid or if an
		// error occurs then SIGNAL_TIME_INVALID is returned.
		nsecs_t getSignalTime() const;

		#if __cplusplus > 201103L

include/ui/FenceTime.h

0 → 100644

+161 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 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.
		*/

		#ifndef ANDROID_FENCE_TIME_H
		#define ANDROID_FENCE_TIME_H

		#include <ui/Fence.h>
		#include <utils/Flattenable.h>
		#include <utils/Timers.h>

		#include <atomic>
		#include <mutex>
		#include <queue>

		namespace android {

		// A wrapper around fence that only implements isValid and getSignalTime.
		// It automatically closes the fence in a thread-safe manner once the signal
		// time is known.
		class FenceTime {
		public:
		// An atomic snapshot of the FenceTime that is flattenable.
		//
		// This class is needed because the FenceTime class may not stay
		// consistent for all steps of the flattening process.
		//
		// Not thread safe.
		struct Snapshot : public Flattenable<Snapshot> {
		enum class State {
		EMPTY,
		FENCE,
		SIGNAL_TIME,
		};

		Snapshot() = default; // Creates an empty snapshot.
		explicit Snapshot(const sp<Fence>& fence);
		explicit Snapshot(nsecs_t signalTime);

		// Movable.
		Snapshot(Snapshot&& src) = default;
		Snapshot& operator=(Snapshot&& src) = default;
		// Not copyable.
		Snapshot(const Snapshot& src) = delete;
		Snapshot& operator=(const Snapshot&& src) = delete;

		// Flattenable implementation.
		size_t getFlattenedSize() const;
		size_t getFdCount() const;
		status_t flatten(void& buffer, size_t& size, int& fds,
		size_t& count) const;
		status_t unflatten(void const& buffer, size_t& size, int const& fds,
		size_t& count);

		State state{State::EMPTY};
		sp<Fence> fence{Fence::NO_FENCE};
		nsecs_t signalTime{Fence::SIGNAL_TIME_INVALID};
		};

		static const std::shared_ptr<FenceTime> NO_FENCE;

		explicit FenceTime(const sp<Fence>& fence);
		explicit FenceTime(sp<Fence>&& fence);

		// Passing in Fence::SIGNAL_TIME_PENDING is not allowed.
		// Doing so will convert the signalTime to Fence::SIGNAL_TIME_INVALID.
		explicit FenceTime(nsecs_t signalTime);

		// Do not allow default construction. Share NO_FENCE or explicitly construct
		// with Fence::SIGNAL_TIME_INVALID instead.
		FenceTime() = delete;

		// Do not allow copy, assign, or move. Use a shared_ptr to share the
		// signalTime result. Or use getSnapshot() if a thread-safe copy is really
		// needed.
		FenceTime(const FenceTime&) = delete;
		FenceTime(FenceTime&&) = delete;
		FenceTime& operator=(const FenceTime&) = delete;
		FenceTime& operator=(FenceTime&&) = delete;

		// This method should only be called when replacing the fence with
		// a signalTime. Since this is an indirect way of setting the signal time
		// of a fence, the snapshot should come from a trusted source.
		void applyTrustedSnapshot(const Snapshot& src);

		bool isValid() const;

		// Attempts to get the timestamp from the Fence if the timestamp isn't
		// already cached. Otherwise, it returns the cached value.
		nsecs_t getSignalTime();

		// Gets the cached timestamp without attempting to query the Fence.
		nsecs_t getCachedSignalTime() const;

		// Returns a snapshot of the FenceTime in its current state.
		Snapshot getSnapshot() const;

		// Override new and delete since this needs 8-byte alignment, which
		// is not guaranteed on x86.
		static void* operator new(size_t nbytes) noexcept;
		static void operator delete(void *p);

		private:
		enum class State {
		VALID,
		INVALID,
		};

		const State mState{State::INVALID};

		// mMutex guards mFence and mSignalTime.
		// mSignalTime is also atomic since it is sometimes read outside the lock
		// for quick checks.
		mutable std::mutex mMutex;
		sp<Fence> mFence{Fence::NO_FENCE};
		std::atomic<nsecs_t> mSignalTime{Fence::SIGNAL_TIME_INVALID};
		};

		// A queue of FenceTimes that are expected to signal in FIFO order.
		// Only maintains a queue of weak pointers so it doesn't keep references
		// to Fences on its own.
		//
		// Can be used to get the signal time of a fence and close its file descriptor
		// without making a syscall for every fence later in the timeline.
		// Additionally, since the FenceTime caches the timestamp internally,
		// other timelines that reference the same FenceTime can avoid the syscall.
		//
		// FenceTimeline only keeps track of a limited number of entries to avoid
		// growing unbounded. Users of FenceTime must make sure they can work even
		// if FenceTimeline did nothing. i.e. they should eventually call
		// Fence::getSignalTime(), not only Fence::getCachedSignalTime().
		//
		// push() and updateSignalTimes() are safe to call simultaneously from
		// different threads.
		class FenceTimeline {
		public:
		static constexpr size_t MAX_ENTRIES = 64;

		void push(const std::shared_ptr<FenceTime>& fence);
		void updateSignalTimes();

		private:
		mutable std::mutex mMutex;
		std::queue<std::weak_ptr<FenceTime>> mQueue;
		};

		}; // namespace android

		#endif // ANDROID_FENCE_TIME_H

libs/ui/Android.bp

+1 −0

Original line number	Diff line number	Diff line
		@@ -43,6 +43,7 @@ cc_library_shared {
		srcs: [
		"ColorSpace.cpp",
		"Fence.cpp",
		"FenceTime.cpp",
		"FrameStats.cpp",
		"Gralloc1.cpp",
		"Gralloc1On0Adapter.cpp",

libs/ui/Fence.cpp

+3 −3

Original line number	Diff line number	Diff line
		@@ -109,17 +109,17 @@ int Fence::dup() const {

		nsecs_t Fence::getSignalTime() const {
		if (mFenceFd == -1) {
		return -1;
		return SIGNAL_TIME_INVALID;
		}

		struct sync_fence_info_data* finfo = sync_fence_info(mFenceFd);
		if (finfo == NULL) {
		ALOGE("sync_fence_info returned NULL for fd %d", mFenceFd);
		return -1;
		return SIGNAL_TIME_INVALID;
		}
		if (finfo->status != 1) {
		sync_fence_info_free(finfo);
		return INT64_MAX;
		return SIGNAL_TIME_PENDING;
		}

		struct sync_pt_info* pinfo = NULL;

libs/ui/FenceTime.cpp

0 → 100644

+282 −0

Original line number	Diff line number	Diff line
		/*
		* 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