posix: Avoid static initializers in static/global mutexes

This patch removes static initializers related to static and
global mutexes from the final library's machine code when
building on a pthread-capable system.

We use PTHREAD_MUTEX_INITIALIZER to perform POD-style
initialization. You need a line like the following to declare
a global mutex with it:

    SkBaseMutex gMutex = { PTHREAD_MUTEX_INITIALIZER };

We introduce the SK_DECLARE_STATIC_MUTEX and SK_DECLARE_GLOBAL_MUTEX
macros to be able to declare static/global mutexes in the source tree
uniformly.

SkMutex is now defined as a sub-class of SkBaseMutex, with standard
construction/destruction semantics. This is useful if the mutex
object is a member of another C++ class, or allocated dynamically.

We also modify a few places to refer to SkBaseMutex instead of a
SkMutex, where it makes sense. Generally speaking, client code
should hold and use pointers to SkBaseMutex whenever they can
now.

We defined a new built-time macro named SK_USE_POSIX_THREADS
to indicate that we're using a pthread-based SkThread.h
interface. The macro will also be used in future patches
to implement other helper thread synchronization classes.

Finally, we inline the acquire() and release() functions in the
case of Posix to improve performance a bit.

Running: 'bench -repeat 10 -match mutex' on an Android device or
a 2.4GHz Xeon Linux desktop shows the following improvements:

                      Before     After

        Galaxy Nexus    1.64      1.45
        Nexus S         1.47      1.16
        Xoom            1.86      1.66
        Xeon            0.36      0.31

This removes 5 static mutex initializers from the library
Review URL: https://codereview.appspot.com/5501066

git-svn-id: http://skia.googlecode.com/svn/trunk@3091 2bbb7eff-a529-9590-31e7-b0007b416f81

bench/MutexBench.cpp

@@ -23,7 +23,7 @@ protected:
 
     virtual void onDraw(SkCanvas* canvas) {
         for (int i = 0; i < N; i++) {
-            SkMutex mu;
+            SK_DECLARE_STATIC_MUTEX(mu);
             for (int j = 0; j < M; j++) {
                 mu.acquire();
                 mu.release();

gyp/common_conditions.gypi

@@ -205,6 +205,14 @@
       },
     ],
 
+    # We can POD-style initialization of static mutexes to avoid generating
+    # static initializers if we're using a pthread-compatible thread interface.
+    [ 'skia_os != "win"', {
+      'defines': [
+        'SK_USE_POSIX_THREADS'
+      ],
+    }],
+
   ], # end 'conditions'
 }
 

include/core/SkPixelRef.h

@@ -52,7 +52,7 @@ class SkGpuTexture;
 */
 class SkPixelRef : public SkRefCnt {
 public:
-    explicit SkPixelRef(SkMutex* mutex = NULL);
+    explicit SkPixelRef(SkBaseMutex* mutex = NULL);
 
     /** Return the pixel memory returned from lockPixels, or null if the
         lockCount is 0.
@@ -201,16 +201,16 @@ protected:
     /** Return the mutex associated with this pixelref. This value is assigned
         in the constructor, and cannot change during the lifetime of the object.
     */
-    SkMutex* mutex() const { return fMutex; }
+    SkBaseMutex* mutex() const { return fMutex; }
 
-    SkPixelRef(SkFlattenableReadBuffer&, SkMutex*);
+    SkPixelRef(SkFlattenableReadBuffer&, SkBaseMutex*);
 
 private:
 #if !SK_ALLOW_STATIC_GLOBAL_INITIALIZERS
     static void InitializeFlattenables();
 #endif
 
-    SkMutex*        fMutex; // must remain in scope for the life of this object
+    SkBaseMutex*    fMutex; // must remain in scope for the life of this object
     void*           fPixels;
     SkColorTable*   fColorTable;    // we do not track ownership, subclass does
     int             fLockCount;

include/core/SkThread.h

@@ -31,7 +31,7 @@ public:
 
 class SkAutoMutexAcquire : SkNoncopyable {
 public:
-    explicit SkAutoMutexAcquire(SkMutex& mutex) : fMutex(&mutex)
+    explicit SkAutoMutexAcquire(SkBaseMutex& mutex) : fMutex(&mutex)
     {
         SkASSERT(fMutex != NULL);
         mutex.acquire();
@@ -55,7 +55,7 @@ public:
     }
         
 private:
-    SkMutex* fMutex;
+    SkBaseMutex* fMutex;
 };
 
 #endif

include/core/SkThread_platform.h

@@ -78,7 +78,44 @@ SK_API int32_t sk_atomic_inc(int32_t* addr);
 */
 SK_API int32_t sk_atomic_dec(int32_t* addr);
 
-class SkMutex {
+#endif
+
+#ifdef SK_USE_POSIX_THREADS
+
+#include <pthread.h>
+
+// A SkBaseMutex is a POD structure that can be directly initialized
+// at declaration time with SK_DECLARE_STATIC/GLOBAL_MUTEX. This avoids the
+// generation of a static initializer in the final machine code (and
+// a corresponding static finalizer).
+//
+struct SkBaseMutex {
+    void    acquire() { pthread_mutex_lock(&fMutex); }
+    void    release() { pthread_mutex_unlock(&fMutex); }
+    pthread_mutex_t  fMutex;
+};
+
+// Using POD-style initialization prevents the generation of a static initializer
+// and keeps the acquire() implementation small and fast.
+#define SK_DECLARE_STATIC_MUTEX(name)   static SkBaseMutex  name = { PTHREAD_MUTEX_INITIALIZER }
+
+// Special case used when the static mutex must be available globally.
+#define SK_DECLARE_GLOBAL_MUTEX(name)   SkBaseMutex  name = { PTHREAD_MUTEX_INITIALIZER }
+
+// A normal mutex that requires 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, SkNoncopyable {
+public:
+    SkMutex();
+    ~SkMutex();
+};
+
+#else // !SK_USE_POSIX_THREADS
+
+// In the generic case, SkBaseMutex and SkMutex are the same thing, and we
+// can't easily get rid of static initializers.
+//
+class SkMutex : SkNoncopyable {
 public:
     SkMutex();
     ~SkMutex();
@@ -94,6 +131,12 @@ private:
     uint32_t    fStorage[kStorageIntCount];
 };
 
-#endif
+typedef SkMutex SkBaseMutex;
+
+#define SK_DECLARE_STATIC_MUTEX(name)  static SkBaseMutex  name
+#define SK_DECLARE_GLOBAL_MUTEX(name)  SkBaseMutex  name
+
+#endif // !SK_USE_POSIX_THREADS
+
 
 #endif

include/pdf/SkPDFFont.h

@@ -196,7 +196,7 @@ private:
 
     // This should be made a hash table if performance is a problem.
     static SkTDArray<FontRec>& CanonicalFonts();
-    static SkMutex& CanonicalFontsMutex();
+    static SkBaseMutex& CanonicalFontsMutex();
 };
 
 #endif

include/pdf/SkPDFGraphicState.h

@@ -86,7 +86,7 @@ private:
 
     // This should be made a hash table if performance is a problem.
     static SkTDArray<GSCanonicalEntry>& CanonicalPaints();
-    static SkMutex& CanonicalPaintsMutex();
+    static SkBaseMutex& CanonicalPaintsMutex();
 
     SkPDFGraphicState();
     explicit SkPDFGraphicState(const SkPaint& paint);

include/pdf/SkPDFShader.h

@@ -56,7 +56,7 @@ protected:
     };
     // This should be made a hash table if performance is a problem.
     static SkTDArray<ShaderCanonicalEntry>& CanonicalShaders();
-    static SkMutex& CanonicalShadersMutex();
+    static SkBaseMutex& CanonicalShadersMutex();
     static void RemoveShader(SkPDFObject* shader);
 
     SkPDFShader();

obsolete/SkGLDevice.cpp

@@ -867,7 +867,7 @@ void SkGLDevice::drawTextOnPath(const SkDraw& draw, const void* text,
 #include "SkTextureCache.h"
 #include "SkThread.h"
 
-static SkMutex gTextureCacheMutex;
+SK_DECLARE_STATIC_MUTEX(gTextureCacheMutex);
 static SkTextureCache gTextureCache(kTexCountMax_Default, kTexSizeMax_Default);
 
 SkGLDevice::TexCache* SkGLDevice::LockTexCache(const SkBitmap& bitmap,

src/core/SkMemory_stdlib.cpp

@@ -29,7 +29,7 @@ static const char kBlockTrailerTag[] = { 'a', 'i', 'k', 's' };
 #define kByteFill 0xCD
 #define kDeleteFill 0xEF
 
-static SkMutex& get_block_mutex() {
+static SkBaseMutex& get_block_mutex() {
     static SkMutex* gBlockMutex;
     if (NULL == gBlockMutex) {
         gBlockMutex = new SkMutex;

src/core/SkPixelRef.cpp

@@ -9,7 +9,7 @@
 #include "SkFlattenable.h"
 #include "SkThread.h"
 
-static SkMutex  gPixelRefMutex;
+SK_DECLARE_STATIC_MUTEX(gPixelRefMutex);
 
 extern int32_t SkNextPixelRefGenerationID();
 int32_t SkNextPixelRefGenerationID() {
@@ -24,7 +24,7 @@ int32_t SkNextPixelRefGenerationID() {
 }
 
 
-SkPixelRef::SkPixelRef(SkMutex* mutex) {
+SkPixelRef::SkPixelRef(SkBaseMutex* mutex) {
     if (NULL == mutex) {
         mutex = &gPixelRefMutex;
     }
@@ -36,7 +36,7 @@ SkPixelRef::SkPixelRef(SkMutex* mutex) {
     fIsImmutable = false;
 }
 
-SkPixelRef::SkPixelRef(SkFlattenableReadBuffer& buffer, SkMutex* mutex) {
+SkPixelRef::SkPixelRef(SkFlattenableReadBuffer& buffer, SkBaseMutex* mutex) {
     if (NULL == mutex) {
         mutex = &gPixelRefMutex;
     }

src/core/SkTypefaceCache.cpp

@@ -82,7 +82,7 @@ SkFontID SkTypefaceCache::NewFontID() {
     return sk_atomic_inc(&gFontID) + 1;
 }
 
-static SkMutex gMutex;
+SK_DECLARE_STATIC_MUTEX(gMutex);
 
 void SkTypefaceCache::Add(SkTypeface* face, SkTypeface::Style requestedStyle) {
     SkAutoMutexAcquire ama(gMutex);

src/effects/SkGradientShader.cpp

@@ -755,7 +755,7 @@ void Gradient_Shader::commonAsABitmap(SkBitmap* bitmap) const {
 
     ///////////////////////////////////
 
-    static SkMutex gMutex;
+    SK_DECLARE_STATIC_MUTEX(gMutex);
     static SkBitmapCache* gCache;
     // each cache cost 1K of RAM, since each bitmap will be 1x256 at 32bpp
     static const int MAX_NUM_CACHED_GRADIENT_BITMAPS = 32;

src/gpu/SkGrTexturePixelRef.cpp

@@ -16,7 +16,7 @@
 
 // since we call lockPixels recursively on fBitmap, we need a distinct mutex,
 // to avoid deadlock with the default one provided by SkPixelRef.
-static SkMutex  gROLockPixelsPixelRefMutex;
+SK_DECLARE_STATIC_MUTEX(gROLockPixelsPixelRefMutex);
 
 SkROLockPixelsPixelRef::SkROLockPixelsPixelRef() : INHERITED(&gROLockPixelsPixelRefMutex) {
 }

src/images/SkImageRef.cpp

@@ -16,7 +16,7 @@
 //#define DUMP_IMAGEREF_LIFECYCLE
 
 // can't be static, as SkImageRef_Pool needs to see it
-SkMutex gImageRefMutex;
+SK_DECLARE_GLOBAL_MUTEX(gImageRefMutex);
 
 ///////////////////////////////////////////////////////////////////////////////
 

src/images/SkImageRef_GlobalPool.cpp

@@ -9,7 +9,7 @@
 #include "SkImageRefPool.h"
 #include "SkThread.h"
 
-extern SkMutex gImageRefMutex;
+extern SkBaseMutex gImageRefMutex;
 
 static SkImageRefPool gGlobalImageRefPool;
 

src/pdf/SkPDFFont.cpp

@@ -797,9 +797,10 @@ SkTDArray<SkPDFFont::FontRec>& SkPDFFont::CanonicalFonts() {
 }
 
 // static
-SkMutex& SkPDFFont::CanonicalFontsMutex() {
-    // This initialization is only thread safe with gcc.
-    static SkMutex gCanonicalFontsMutex;
+SkBaseMutex& SkPDFFont::CanonicalFontsMutex() {
+    // This initialization is only thread safe with gcc, or when
+    // POD-style mutex initialization is used.
+    SK_DECLARE_STATIC_MUTEX(gCanonicalFontsMutex);
     return gCanonicalFontsMutex;
 }
 

src/pdf/SkPDFGraphicState.cpp

@@ -85,9 +85,10 @@ SkPDFGraphicState::CanonicalPaints() {
 }
 
 // static
-SkMutex& SkPDFGraphicState::CanonicalPaintsMutex() {
-    // This initialization is only thread safe with gcc.
-    static SkMutex gCanonicalPaintsMutex;
+SkBaseMutex& SkPDFGraphicState::CanonicalPaintsMutex() {
+    // This initialization is only thread safe with gcc or when
+    // POD-style mutex initialization is used.
+    SK_DECLARE_STATIC_MUTEX(gCanonicalPaintsMutex);
     return gCanonicalPaintsMutex;
 }
 

src/pdf/SkPDFShader.cpp

@@ -391,9 +391,10 @@ SkTDArray<SkPDFShader::ShaderCanonicalEntry>& SkPDFShader::CanonicalShaders() {
 }
 
 // static
-SkMutex& SkPDFShader::CanonicalShadersMutex() {
-    // This initialization is only thread safe with gcc.
-    static SkMutex gCanonicalShadersMutex;
+SkBaseMutex& SkPDFShader::CanonicalShadersMutex() {
+    // This initialization is only thread safe with gcc or when
+    // POD-style mutex initialization is used.
+    SK_DECLARE_STATIC_MUTEX(gCanonicalShadersMutex);
     return gCanonicalShadersMutex;
 }
 

src/ports/SkFontHost_FreeType.cpp

@@ -88,7 +88,7 @@ static bool isLCD(const SkScalerContext::Rec& rec) {
 
 struct SkFaceRec;
 
-static SkMutex      gFTMutex;
+SK_DECLARE_STATIC_MUTEX(gFTMutex);
 static int          gFTCount;
 static FT_Library   gFTLibrary;
 static SkFaceRec*   gFaceRecHead;

src/ports/SkFontHost_android.cpp

@@ -67,7 +67,7 @@ struct NameFamilyPair {
 static int32_t gUniqueFontID;
 
 // this is the mutex that protects these globals
-static SkMutex gFamilyMutex;
+SK_DECLARE_STATIC_MUTEX(gFamilyMutex);
 static FamilyRec* gFamilyHead;
 static SkTDArray<NameFamilyPair> gNameList;
 

src/ports/SkFontHost_fontconfig.cpp

@@ -38,7 +38,7 @@ SkTypeface::Style find_name_and_style(SkStream* stream, SkString* name);
 // Although truetype fonts can support multiple faces in a single file, at the
 // moment Skia doesn't.
 // -----------------------------------------------------------------------------
-static SkMutex global_fc_map_lock;
+SK_DECLARE_STATIC_MUTEX(global_fc_map_lock);
 static std::map<std::string, unsigned> global_fc_map;
 static std::map<unsigned, std::string> global_fc_map_inverted;
 static std::map<uint32_t, SkTypeface *> global_fc_typefaces;

src/ports/SkFontHost_linux.cpp

@@ -60,7 +60,7 @@ struct NameFamilyPair {
 static int32_t gUniqueFontID;
 
 // this is the mutex that protects these globals
-static SkMutex gFamilyMutex;
+SK_DECLARE_STATIC_MUTEX(gFamilyMutex);
 static FamilyRec* gFamilyHead;
 static SkTDArray<NameFamilyPair> gNameList;
 

src/ports/SkFontHost_mac_atsui.cpp

@@ -16,7 +16,7 @@
 #include "SkPoint.h"
 
 const char* gDefaultfont = "Arial"; // hard code for now
-static SkMutex      gFTMutex;
+SK_DECLARE_STATIC_MUTEX(gFTMutex);
 
 static inline SkPoint F32PtToSkPoint(const Float32Point p) {
     SkPoint sp = { SkFloatToScalar(p.x), SkFloatToScalar(p.y) };

src/ports/SkFontHost_mac_coretext.cpp

@@ -450,7 +450,7 @@ static CTFontRef GetFontRefFromFontID(SkFontID fontID) {
 }
 
 static SkTypeface* GetDefaultFace() {
-    static SkMutex gMutex;
+    SK_DECLARE_STATIC_MUTEX(gMutex);
     SkAutoMutexAcquire ma(gMutex);
 
     static SkTypeface* gDefaultFace;

src/ports/SkFontHost_simple.cpp

@@ -59,7 +59,7 @@ struct NameFamilyPair {
 static int32_t gUniqueFontID;
 
 // this is the mutex that protects these globals
-static SkMutex gFamilyMutex;
+SK_DECLARE_STATIC_MUTEX(gFamilyMutex);
 static FamilyRec* gFamilyHead;
 static SkTDArray<NameFamilyPair> gNameList;
 

src/ports/SkFontHost_win.cpp

@@ -448,7 +448,7 @@ static FIXED float2FIXED(float x) {
     return SkFixedToFIXED(SkFloatToFixed(x));
 }
 
-static SkMutex gFTMutex;
+SK_DECLARE_STATIC_MUTEX(gFTMutex);
 
 #define HIRES_TEXTSIZE  2048
 #define HIRES_SHIFT     11

src/ports/SkThread_pthread.cpp

@@ -55,7 +55,7 @@ int32_t sk_atomic_inc(int32_t* addr)
 int32_t sk_atomic_dec(int32_t* addr)
 {
     SkAutoMutexAcquire ac(gAtomicMutex);
-    
+
     int32_t value = *addr;
     *addr = value - 1;
     return value;
@@ -83,6 +83,30 @@ static void print_pthread_error(int status) {
     }
 }
 
+#ifdef SK_USE_POSIX_THREADS
+
+SkMutex::SkMutex() {
+    int status;
+
+    status = pthread_mutex_init(&fMutex, NULL);
+    if (status != 0) {
+        print_pthread_error(status);
+        SkASSERT(0 == status);
+    }
+}
+
+SkMutex::~SkMutex() {
+    int status = pthread_mutex_destroy(&fMutex);
+
+    // only report errors on non-global mutexes
+    if (status != 0) {
+        print_pthread_error(status);
+        SkASSERT(0 == status);
+    }
+}
+
+#else // !SK_USE_POSIX_THREADS
+
 SkMutex::SkMutex() {
     if (sizeof(pthread_mutex_t) > sizeof(fStorage)) {
         SkDEBUGF(("pthread mutex size = %d\n", sizeof(pthread_mutex_t)));
@@ -124,3 +148,4 @@ void SkMutex::release() {
     SkASSERT(0 == status);
 }
 
+#endif // !SK_USE_POSIX_THREADS

src/views/SkEventSink.cpp

@@ -260,7 +260,7 @@ SkEventSink* SkEventSink::FindSink(SkEventSinkID sinkID)
 #include "SkTDict.h"
 
 #define kMinStringBufferSize    128
-static SkMutex                  gNamedSinkMutex;
+SK_DECLARE_STATIC_MUTEX(gNamedSinkMutex);
 static SkTDict<SkEventSinkID>   gNamedSinkIDs(kMinStringBufferSize);
 
 /** Register a name/id pair with the system. If the name already exists,