Make mutex semaphore based.

include/ports/SkMutex_pthread.h

-/*
- * Copyright 2013 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkMutex_pthread_DEFINED
-#define SkMutex_pthread_DEFINED
-
-/** Posix pthread_mutex based mutex. */
-
-#include <errno.h>
-#include <pthread.h>
-
-// We use error-checking mutexes in Debug builds or normal fast mutexes in Release builds.
-// Debug builds get these checks for free:
-//   - a double acquire() from the same thread fails immediately instead of deadlocking;
-//   - release() checks that the mutex is being unlocked by its owner thread.
-// I don't see a built-in way to implement assertHeld(), so we track that with an fOwner field.
-
-// This isn't technically portable, but on Linux and Android pthread_t is some sort of int, and
-// on Darwin it's a pointer.  So assuming pthread_self() never returns 0, it works as a sentinel.
-SkDEBUGCODE(static const pthread_t kNoOwner = 0;)
-
-// An SkBaseMutex is a POD structure that can be directly initialized at declaration time with
-// SK_DECLARE_STATIC_MUTEX. This avoids the generation of a static initializer in the final
-// machine code (and a corresponding static finalizer).
-struct SkBaseMutex {
-    void acquire() {
-        SkDEBUGCODE(int rc = ) pthread_mutex_lock(&fMutex);
-        SkASSERT(0 == rc);
-        SkDEBUGCODE(fOwner = pthread_self();)
-    }
-    void release() {
-        this->assertHeld();  // Usually redundant, but not for static mutexes on Macs (see below).
-        SkDEBUGCODE(fOwner = kNoOwner;)
-        SkDEBUGCODE(int rc = ) pthread_mutex_unlock(&fMutex);
-        SkASSERT(0 == rc);
-    }
-    void assertHeld() {
-        SkASSERT(0 != pthread_equal(fOwner, pthread_self()));
-    }
-
-    pthread_mutex_t fMutex;
-    SkDEBUGCODE(pthread_t fOwner;)  // Read and write only when holding fMutex.
-};
-
-// A normal mutex that's required to be initialized through normal C++ construction,
-// i.e. when it's a member of another class, or allocated on the heap.
-class SkMutex : public SkBaseMutex {
-public:
-    SkMutex() {
-#ifdef SK_DEBUG
-        pthread_mutexattr_t attr;
-        SkASSERT(0 == pthread_mutexattr_init(&attr));
-        SkASSERT(0 == pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK));
-        SkASSERT(0 == pthread_mutex_init(&fMutex, &attr));
-        SkASSERT(0 == pthread_mutexattr_destroy(&attr));
-        fOwner = kNoOwner;
-#else
-        (void)pthread_mutex_init(&fMutex, NULL);
-#endif
-    }
-
-    ~SkMutex() {
-        SkDEBUGCODE(int rc = )pthread_mutex_destroy(&fMutex);
-        SkASSERT(0 == rc);
-    }
-
-private:
-    SkMutex(const SkMutex&);
-    SkMutex& operator=(const SkMutex&);
-};
-
-#if defined(SK_DEBUG) && defined(PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP)
-    // When possible we want to use error-check mutexes in Debug builds.  See the note at the top.
-    #define SK_BASE_MUTEX_INIT { PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP, kNoOwner }
-#elif defined(SK_DEBUG)
-    // Macs don't support PTHREAD_ERRORCHECK_MUTEX_INITIALIZER when targeting <10.7. We target 10.6.
-    #define SK_BASE_MUTEX_INIT { PTHREAD_MUTEX_INITIALIZER, kNoOwner }
-#else
-    #define SK_BASE_MUTEX_INIT { PTHREAD_MUTEX_INITIALIZER }
-#endif
-
-// Using POD-style initialization prevents the generation of a static initializer.
-//
-// Without magic statics there are no thread safety guarantees on initialization
-// of local statics (even POD). As a result, it is illegal to use
-// SK_DECLARE_STATIC_MUTEX in a function.
-//
-// Because SkBaseMutex is not a primitive, a static SkBaseMutex cannot be
-// initialized in a class with this macro.
-#define SK_DECLARE_STATIC_MUTEX(name) namespace {} static SkBaseMutex name = SK_BASE_MUTEX_INIT
-
-#endif