/* * Copyright (C) 2007 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_UI_SHARED_BUFFER_STACK_H #define ANDROID_UI_SHARED_BUFFER_STACK_H #include <stdint.h> #include <sys/types.h> #include <cutils/compiler.h> #include <utils/Debug.h> #include <utils/threads.h> #include <utils/String8.h> #include <ui/Rect.h> namespace android { // --------------------------------------------------------------------------- /* * These classes manage a stack of buffers in shared memory. * * SharedClient: represents a client with several stacks * SharedBufferStack: represents a stack of buffers * SharedBufferClient: manipulates the SharedBufferStack from the client side * SharedBufferServer: manipulates the SharedBufferStack from the server side * * Buffers can be dequeued until there are none available, they can be locked * unless they are in use by the server, which is only the case for the last * dequeue-able buffer. When these various conditions are not met, the caller * waits until the condition is met. * * * CAVEATS: * * In the current implementation there are several limitations: * - buffers must be locked in the same order they've been dequeued * - buffers must be enqueued in the same order they've been locked * - dequeue() is not reentrant * - no error checks are done on the condition above * */ // When changing these values, the COMPILE_TIME_ASSERT at the end of this // file need to be updated. const unsigned int NUM_LAYERS_MAX = 31; const unsigned int NUM_BUFFER_MAX = 4; const unsigned int NUM_DISPLAY_MAX = 4; // ---------------------------------------------------------------------------- class Region; class SharedBufferStack; class SharedClient; // ---------------------------------------------------------------------------- struct FlatRegion { // 12 bytes static const unsigned int NUM_RECT_MAX = 1; uint32_t count; uint16_t rects[4*NUM_RECT_MAX]; }; // should be 128 bytes (32 longs) class SharedBufferStack { friend class SharedClient; friend class SharedBufferBase; friend class SharedBufferClient; friend class SharedBufferServer; public: SharedBufferStack(); status_t setDirtyRegion(int buffer, const Region& reg); Region getDirtyRegion(int buffer) const; // these attributes are part of the conditions/updates volatile int32_t head; // server's current front buffer volatile int32_t available; // number of dequeue-able buffers volatile int32_t queued; // number of buffers waiting for post volatile int32_t inUse; // buffer currently in use by SF // not part of the conditions volatile int32_t reallocMask; int32_t identity; // surface's identity (const) status_t status; // surface's status code int32_t reserved32[13]; FlatRegion dirtyRegion[NUM_BUFFER_MAX]; // 12*4=48 bytes }; // ---------------------------------------------------------------------------- // 4 KB max class SharedClient { public: SharedClient(); ~SharedClient(); status_t validate(size_t token) const; uint32_t getIdentity(size_t token) const; status_t setIdentity(size_t token, uint32_t identity); private: friend class SharedBufferBase; friend class SharedBufferClient; friend class SharedBufferServer; // FIXME: this should be replaced by a lock-less primitive Mutex lock; Condition cv; SharedBufferStack surfaces[ NUM_LAYERS_MAX ]; }; // ============================================================================ class SharedBufferBase { public: SharedBufferBase(SharedClient* sharedClient, int surface, int num); ~SharedBufferBase(); uint32_t getIdentity(); size_t getFrontBuffer() const; String8 dump(char const* prefix) const; protected: SharedClient* const mSharedClient; SharedBufferStack* const mSharedStack; const int mNumBuffers; friend struct Update; friend struct QueueUpdate; struct ConditionBase { SharedBufferStack& stack; inline ConditionBase(SharedBufferBase* sbc) : stack(*sbc->mSharedStack) { } }; struct UpdateBase { SharedBufferStack& stack; inline UpdateBase(SharedBufferBase* sbb) : stack(*sbb->mSharedStack) { } }; template <typename T> status_t waitForCondition(T condition); template <typename T> status_t updateCondition(T update); }; template <typename T> status_t SharedBufferBase::waitForCondition(T condition) { SharedClient& client( *mSharedClient ); const nsecs_t TIMEOUT = s2ns(1); Mutex::Autolock _l(client.lock); while (!condition()) { status_t err = client.cv.waitRelative(client.lock, TIMEOUT); // handle errors and timeouts if (CC_UNLIKELY(err != NO_ERROR)) { if (err == TIMED_OUT) { if (condition()) { LOGE("waitForCondition(%s) timed out (identity=%d), " "but condition is true! We recovered but it " "shouldn't happen." , T::name(), mSharedStack->identity); break; } else { LOGW("waitForCondition(%s) timed out (identity=%d). " "CPU may be pegged. trying again.", T::name(), mSharedStack->identity); } } else { LOGE("waitForCondition(%s) error (%s) ", T::name(), strerror(-err)); return err; } } } return NO_ERROR; } template <typename T> status_t SharedBufferBase::updateCondition(T update) { SharedClient& client( *mSharedClient ); Mutex::Autolock _l(client.lock); ssize_t result = update(); client.cv.broadcast(); return result; } // ---------------------------------------------------------------------------- class SharedBufferClient : public SharedBufferBase { public: SharedBufferClient(SharedClient* sharedClient, int surface, int num); ssize_t dequeue(); status_t undoDequeue(int buf); status_t lock(int buf); status_t queue(int buf); bool needNewBuffer(int buffer) const; status_t setDirtyRegion(int buffer, const Region& reg); private: friend struct Condition; friend struct DequeueCondition; friend struct LockCondition; struct QueueUpdate : public UpdateBase { inline QueueUpdate(SharedBufferBase* sbb); inline ssize_t operator()(); }; struct UndoDequeueUpdate : public UpdateBase { inline UndoDequeueUpdate(SharedBufferBase* sbb); inline ssize_t operator()(); }; // -- struct DequeueCondition : public ConditionBase { inline DequeueCondition(SharedBufferClient* sbc); inline bool operator()(); static inline const char* name() { return "DequeueCondition"; } }; struct LockCondition : public ConditionBase { int buf; inline LockCondition(SharedBufferClient* sbc, int buf); inline bool operator()(); static inline const char* name() { return "LockCondition"; } }; int32_t tail; }; // ---------------------------------------------------------------------------- class SharedBufferServer : public SharedBufferBase { public: SharedBufferServer(SharedClient* sharedClient, int surface, int num); ssize_t retireAndLock(); status_t unlock(int buffer); status_t reallocate(); status_t assertReallocate(int buffer); Region getDirtyRegion(int buffer) const; private: struct UnlockUpdate : public UpdateBase { const int lockedBuffer; inline UnlockUpdate(SharedBufferBase* sbb, int lockedBuffer); inline ssize_t operator()(); }; struct RetireUpdate : public UpdateBase { const int numBuffers; inline RetireUpdate(SharedBufferBase* sbb, int numBuffers); inline ssize_t operator()(); }; struct ReallocateCondition : public ConditionBase { int buf; inline ReallocateCondition(SharedBufferBase* sbb, int buf); inline bool operator()(); static inline const char* name() { return "ReallocateCondition"; } }; }; // =========================================================================== struct display_cblk_t { uint16_t w; uint16_t h; uint8_t format; uint8_t orientation; uint8_t reserved[2]; float fps; float density; float xdpi; float ydpi; uint32_t pad[2]; }; struct surface_flinger_cblk_t // 4KB max { uint8_t connected; uint8_t reserved[3]; uint32_t pad[7]; display_cblk_t displays[NUM_DISPLAY_MAX]; }; // --------------------------------------------------------------------------- COMPILE_TIME_ASSERT(sizeof(SharedClient) <= 4096) COMPILE_TIME_ASSERT(sizeof(SharedBufferStack) == 128) COMPILE_TIME_ASSERT(sizeof(surface_flinger_cblk_t) <= 4096) // --------------------------------------------------------------------------- }; // namespace android #endif /* ANDROID_UI_SHARED_BUFFER_STACK_H */