Modernize SkMutex and SkSemaphore.

src/core/SkSemaphore.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "../private/SkSemaphore.h"
 
 #if defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_IOS)
@@ skipping 39 matching lines @@
         void signal(int n) { while (n --> 0) { sem_post(&fSemaphore); } }
         void wait() {
             // Try until we're not interrupted.
             while(sem_wait(&fSemaphore) == -1 && errno == EINTR);
         }
     };
 #endif
 
 ///////////////////////////////////////////////////////////////////////////////
 
-void SkBaseSemaphore::signal(int n) {
-    SkASSERT(n >= 0);
-
-    // We only want to call the OS semaphore when our logical count crosses
-    // from <= 0 to >0 (when we need to wake sleeping threads).
-    //
-    // This is easiest to think about with specific examples of prev and n.
-    // If n == 5 and prev == -3, there are 3 threads sleeping and we signal
-    // SkTMin(-(-3), 5) == 3 times on the OS semaphore, leaving the count at 2.
-    //
-    // If prev >= 0, no threads are waiting, SkTMin(-prev, n) is always <= 0,
-    // so we don't call the OS semaphore, leaving the count at (prev + n).
-    int prev = sk_atomic_fetch_add(&fCount, n, sk_memory_order_release);
-    int toSignal = SkTMin(-prev, n);
-    if (toSignal > 0) {
-        this->osSignal(toSignal);
-    }
+void SkBaseSemaphore::osSignal(int n) {
+    fOSSemaphoreOnce([this] { fOSSemaphore = new OSSemaphore; });
+    fOSSemaphore->signal(n);
 }
 
-static SkBaseSemaphore::OSSemaphore* semaphore(SkBaseSemaphore* semaphore) {
-    return semaphore->fOSSemaphore.get([](){ return new SkBaseSemaphore::OSSemaphore(); });
+void SkBaseSemaphore::osWait() {
+    fOSSemaphoreOnce([this] { fOSSemaphore = new OSSemaphore; });
+    fOSSemaphore->wait();
 }
 
-void SkBaseSemaphore::osSignal(int n) { semaphore(this)->signal(n); }
-
-void SkBaseSemaphore::osWait() { semaphore(this)->wait(); }
-
-void SkBaseSemaphore::deleteSemaphore() {
-    delete (OSSemaphore*) fOSSemaphore;
+void SkBaseSemaphore::cleanup() {
+    delete fOSSemaphore;
 }
-
-///////////////////////////////////////////////////////////////////////////////
-
-SkSemaphore::SkSemaphore(){ fBaseSemaphore = {0, {0}}; }
-
-SkSemaphore::~SkSemaphore() { fBaseSemaphore.deleteSemaphore(); }
-
-void SkSemaphore::wait() { fBaseSemaphore.wait(); }
-
-void SkSemaphore::signal(int n) {fBaseSemaphore.signal(n); }