The Tor Browser: comparison gfx/skia/trunk/include/utils/SkThreadPool.h

--1:000000000000
+:b5de9e0fcc0a
+/*
+* Copyright 2012 Google Inc.
+*
+* Use of this source code is governed by a BSD-style license that can be
+* found in the LICENSE file.
+*/
+#ifndef SkThreadPool_DEFINED
+#define SkThreadPool_DEFINED
+#include "SkCondVar.h"
+#include "SkRunnable.h"
+#include "SkTDArray.h"
+#include "SkTInternalLList.h"
+#include "SkThreadUtils.h"
+#include "SkTypes.h"
+#if defined(SK_BUILD_FOR_UNIX) || defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_ANDROID)
+#    include <unistd.h>
+#endif
+// Returns the number of cores on this machine.
+static inline int num_cores() {
+#if defined(SK_BUILD_FOR_WIN32)
+SYSTEM_INFO sysinfo;
+GetSystemInfo(&sysinfo);
+return sysinfo.dwNumberOfProcessors;
+#elif defined(SK_BUILD_FOR_UNIX) || defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_ANDROID)
+return sysconf(_SC_NPROCESSORS_ONLN);
+#else
+return 1;
+#endif
+}
+template <typename T>
+class SkTThreadPool {
+public:
+/**
+* Create a threadpool with count threads, or one thread per core if kThreadPerCore.
+*/
+static const int kThreadPerCore = -1;
+explicit SkTThreadPool(int count);
+~SkTThreadPool();
+/**
+* Queues up an SkRunnable to run when a thread is available, or synchronously if count is 0.
+* Does not take ownership. NULL is a safe no-op.  If T is not void, the runnable will be passed
+* a reference to a T on the thread's local stack.
+*/
+void add(SkTRunnable<T>*);
+/**
+* Block until all added SkRunnables have completed.  Once called, calling add() is undefined.
+*/
+void wait();
+private:
+struct LinkedRunnable {
+SkTRunnable<T>* fRunnable;  // Unowned.
+SK_DECLARE_INTERNAL_LLIST_INTERFACE(LinkedRunnable);
+};
+enum State {
+kRunning_State,  // Normal case.  We've been constructed and no one has called wait().
+kWaiting_State,  // wait has been called, but there still might be work to do or being done.
+kHalting_State,  // There's no work to do and no thread is busy.  All threads can shut down.
+};
+SkTInternalLList<LinkedRunnable> fQueue;
+SkCondVar                        fReady;
+SkTDArray<SkThread*>             fThreads;
+State                            fState;
+int                              fBusyThreads;
+static void Loop(void*);  // Static because we pass in this.
+};
+template <typename T>
+SkTThreadPool<T>::SkTThreadPool(int count) : fState(kRunning_State), fBusyThreads(0) {
+if (count < 0) {
+count = num_cores();
+}
+// Create count threads, all running SkTThreadPool::Loop.
+for (int i = 0; i < count; i++) {
+SkThread* thread = SkNEW_ARGS(SkThread, (&SkTThreadPool::Loop, this));
+*fThreads.append() = thread;
+thread->start();
+}
+}
+template <typename T>
+SkTThreadPool<T>::~SkTThreadPool() {
+if (kRunning_State == fState) {
+this->wait();
+}
+}
+namespace SkThreadPoolPrivate {
+template <typename T>
+struct ThreadLocal {
+void run(SkTRunnable<T>* r) { r->run(data); }
+T data;
+};
+template <>
+struct ThreadLocal<void> {
+void run(SkTRunnable<void>* r) { r->run(); }
+};
+}  // namespace SkThreadPoolPrivate
+template <typename T>
+void SkTThreadPool<T>::add(SkTRunnable<T>* r) {
+if (r == NULL) {
+return;
+}
+if (fThreads.isEmpty()) {
+SkThreadPoolPrivate::ThreadLocal<T> threadLocal;
+threadLocal.run(r);
+return;
+}
+LinkedRunnable* linkedRunnable = SkNEW(LinkedRunnable);
+linkedRunnable->fRunnable = r;
+fReady.lock();
+SkASSERT(fState != kHalting_State);  // Shouldn't be able to add work when we're halting.
+fQueue.addToHead(linkedRunnable);
+fReady.signal();
+fReady.unlock();
+}
+template <typename T>
+void SkTThreadPool<T>::wait() {
+fReady.lock();
+fState = kWaiting_State;
+fReady.broadcast();
+fReady.unlock();
+// Wait for all threads to stop.
+for (int i = 0; i < fThreads.count(); i++) {
+fThreads[i]->join();
+SkDELETE(fThreads[i]);
+}
+SkASSERT(fQueue.isEmpty());
+}
+template <typename T>
+/*static*/ void SkTThreadPool<T>::Loop(void* arg) {
+// The SkTThreadPool passes itself as arg to each thread as they're created.
+SkTThreadPool<T>* pool = static_cast<SkTThreadPool<T>*>(arg);
+SkThreadPoolPrivate::ThreadLocal<T> threadLocal;
+while (true) {
+// We have to be holding the lock to read the queue and to call wait.
+pool->fReady.lock();
+while(pool->fQueue.isEmpty()) {
+// Does the client want to stop and are all the threads ready to stop?
+// If so, we move into the halting state, and whack all the threads so they notice.
+if (kWaiting_State == pool->fState && pool->fBusyThreads == 0) {
+pool->fState = kHalting_State;
+pool->fReady.broadcast();
+}
+// Any time we find ourselves in the halting state, it's quitting time.
+if (kHalting_State == pool->fState) {
+pool->fReady.unlock();
+return;
+}
+// wait yields the lock while waiting, but will have it again when awoken.
+pool->fReady.wait();
+}
+// We've got the lock back here, no matter if we ran wait or not.
+// The queue is not empty, so we have something to run.  Claim it.
+LinkedRunnable* r = pool->fQueue.tail();
+pool->fQueue.remove(r);
+// Having claimed our SkRunnable, we now give up the lock while we run it.
+// Otherwise, we'd only ever do work on one thread at a time, which rather
+// defeats the point of this code.
+pool->fBusyThreads++;
+pool->fReady.unlock();
+// OK, now really do the work.
+threadLocal.run(r->fRunnable);
+SkDELETE(r);
+// Let everyone know we're not busy.
+pool->fReady.lock();
+pool->fBusyThreads--;
+pool->fReady.unlock();
+}
+SkASSERT(false); // Unreachable.  The only exit happens when pool->fState is kHalting_State.
+}
+typedef SkTThreadPool<void> SkThreadPool;
+#endif

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comparison: gfx/skia/trunk/include/utils/SkThreadPool.h

gfx/skia/trunk/include/utils/SkThreadPool.h