Add global fontconfig lock.

src/fonts/SkFontMgr_fontconfig.cpp

Index: src/fonts/SkFontMgr_fontconfig.cpp
diff --git a/src/fonts/SkFontMgr_fontconfig.cpp b/src/fonts/SkFontMgr_fontconfig.cpp
index bd4c8ddc1db2a275b51c4d0b586efadcbf183b0d..af460b0180ffe086bb5570accaa77fe071780e4a 100644
--- a/src/fonts/SkFontMgr_fontconfig.cpp
+++ b/src/fonts/SkFontMgr_fontconfig.cpp
@@ -12,6 +12,34 @@
 #include "SkMath.h"
 #include "SkString.h"
 #include "SkTDArray.h"
+#include "SkThread.h"
+
+namespace {
+
+// See skia:1497 for background.
+
+#if FC_VERSION < 21091

[bungeman-skia, 2014/03/31 17:25:51]

I'm not sure that it makes sense to use the version we compile against instead
of the runtime version (use FcGetVersion)?

[mtklein, 2014/03/31 17:37:36]

Duh, fixed.

+
+// Fontconfig is not threadsafe.  We sadly need to manually synchronize all Fc...() calls.
+SK_DECLARE_STATIC_MUTEX(gFCMutex);
+static bool gFCSafeToUse;
+
+struct FCLocker {
+    FCLocker() { gFCMutex.acquire(); gFCSafeToUse = true; }
+    ~FCLocker() { gFCSafeToUse = false; gFCMutex.release(); }
+};
+
+#else
+
+// Fontconfig is threadsafe.  Noops for locking.
+static const bool gFCSafeToUse = true;
+struct FCLocker {
+    FCLocker() {}  // Stifles unused variable warnings.
+};
+
+#endif
+
+} // namespace
 
 // for now we pull these in directly. eventually we will solely rely on the
 // SkFontConfigInterface instance.
@@ -40,6 +68,7 @@ static bool is_lower(char c) {
 }
 
 static int get_int(FcPattern* pattern, const char field[]) {
+    SkASSERT(gFCSafeToUse);
     int value;
     if (FcPatternGetInteger(pattern, field, 0, &value) != FcResultMatch) {
         value = SK_MinS32;
@@ -48,6 +77,7 @@ static int get_int(FcPattern* pattern, const char field[]) {
 }
 
 static const char* get_name(FcPattern* pattern, const char field[]) {
+    SkASSERT(gFCSafeToUse);
     const char* name;
     if (FcPatternGetString(pattern, field, 0, (FcChar8**)&name) != FcResultMatch) {
         name = "";
@@ -56,6 +86,7 @@ static const char* get_name(FcPattern* pattern, const char field[]) {
 }
 
 static bool valid_pattern(FcPattern* pattern) {
+    SkASSERT(gFCSafeToUse);
     FcBool is_scalable;
     if (FcPatternGetBool(pattern, FC_SCALABLE, 0, &is_scalable) != FcResultMatch || !is_scalable) {
         return false;
@@ -208,6 +239,8 @@ protected:
     }
 
     virtual SkFontStyleSet* onMatchFamily(const char familyName[]) const SK_OVERRIDE {
+        FCLocker lock;
+
         FcPattern* pattern = FcPatternCreate();
 
         FcPatternAddString(pattern, FC_FAMILY, (FcChar8*)familyName);
@@ -284,6 +317,7 @@ protected:
 
     virtual SkTypeface* onLegacyCreateTypeface(const char familyName[],
                                                unsigned styleBits) const SK_OVERRIDE {
+        FCLocker lock;
         return FontConfigTypeface::LegacyCreateTypeface(NULL, familyName,
                                                   (SkTypeface::Style)styleBits);
     }