add more locking around GlyphStore and FontStack

this is a stopgap until we have a solution that gives every worker thread their own copy

include/mbgl/util/uv.hpp

@@ -60,6 +60,39 @@ private:
     rwlock *mtx = nullptr;
 };
 
+template <class T>
+class exclusive {
+public:
+    exclusive(T& val, mutex &mtx) : ptr(&val), lock(mtx) {}
+    exclusive(T *val, mutex &mtx) : ptr(val), lock(mtx) {}
+    exclusive(mutex &mtx) : lock(mtx) {}
+    exclusive(const std::unique_ptr<mutex> &mtx) : lock(mtx) {}
+    exclusive(const exclusive &) = delete;
+    exclusive(exclusive &&) = default;
+    exclusive &operator=(const exclusive &) = delete;
+    exclusive &operator=(exclusive &&) = default;
+
+    T *operator->() { return ptr; }
+    const T *operator->() const { return ptr; }
+    T *operator*() { return ptr; }
+    const T *operator*() const { return ptr; }
+    operator T&() { return *ptr; }
+    operator const T&() const { return *ptr; }
+
+    void operator<<(T& val) { operator<<(&val); }
+    void operator<<(T *val) {
+        if (ptr) {
+            throw std::runtime_error("exclusive<> was assigned before");
+        }
+        ptr = val;
+    }
+
+private:
+    T *ptr = nullptr;
+    lock lock;
+};
+
+
 
 const char *getFileRequestError(uv_fs_t *req);
 

src/mbgl/renderer/symbol_bucket.cpp

@@ -172,7 +172,7 @@ void SymbolBucket::addFeatures(const VectorTileLayer &layer, const FilterExpress
     if (layout.text.justify == TextJustifyType::Right) justify = 1;
     else if (layout.text.justify == TextJustifyType::Left) justify = 0;
 
-    const FontStack &fontStack = glyphStore.getFontStack(layout.text.font);
+    const auto &fontStack = glyphStore.getFontStack(layout.text.font);
 
     for (const SymbolFeature &feature : features) {
         if (!feature.geometry.size()) continue;
@@ -183,7 +183,7 @@ void SymbolBucket::addFeatures(const VectorTileLayer &layer, const FilterExpress
 
         // if feature has text, shape the text
         if (feature.label.length()) {
-            shaping = fontStack.getShaping(
+            shaping = fontStack->getShaping(
                 /* string */ feature.label,
                 /* maxWidth: ems */ layout.text.max_width * 24,
                 /* lineHeight: ems */ layout.text.line_height * 24,

src/mbgl/text/glyph_store.cpp

@@ -223,7 +223,7 @@ void GlyphPBF::parse(FontStack &stack) {
     data.clear();
 }
 
-GlyphStore::GlyphStore(FileSource& fileSource_) : fileSource(fileSource_) {}
+GlyphStore::GlyphStore(FileSource& fileSource_) : fileSource(fileSource_), mtx(util::make_unique<uv::mutex>()) {}
 
 void GlyphStore::setURL(const std::string &url) {
     glyphURL = url;
@@ -237,15 +237,14 @@ void GlyphStore::waitForGlyphRanges(const std::string &fontStack, const std::set
         return;
     }
 
-    FontStack *stack = nullptr;
+    uv::exclusive<FontStack> stack(mtx);
 
     std::vector<std::shared_future<GlyphPBF &>> futures;
     futures.reserve(glyphRanges.size());
     {
-        std::lock_guard<std::mutex> lock(mtx);
         auto &rangeSets = ranges[fontStack];
 
-        stack = &createFontStack(fontStack);
+        stack << createFontStack(fontStack);
 
         // Attempt to load the glyph range. If the GlyphSet already exists, we are getting back
         // the same shared_future.
@@ -258,7 +257,7 @@ void GlyphStore::waitForGlyphRanges(const std::string &fontStack, const std::set
     // When we get a result (or the GlyphSet is aready loaded), we are attempting to parse the
     // GlyphSet.
     for (std::shared_future<GlyphPBF &> &future : futures) {
-        future.get().parse(*stack);
+        future.get().parse(stack);
     }
 }
 
@@ -277,12 +276,14 @@ FontStack &GlyphStore::createFontStack(const std::string &fontStack) {
     if (stack_it == stacks.end()) {
         stack_it = stacks.emplace(fontStack, util::make_unique<FontStack>()).first;
     }
+
     return *stack_it->second.get();
 }
 
-FontStack &GlyphStore::getFontStack(const std::string &fontStack) {
-    std::lock_guard<std::mutex> lock(mtx);
-    return createFontStack(fontStack);
+uv::exclusive<FontStack> GlyphStore::getFontStack(const std::string &fontStack) {
+    uv::exclusive<FontStack> stack(mtx);
+    stack << createFontStack(fontStack);
+    return stack;
 }
 
 

src/mbgl/text/glyph_store.hpp

@@ -5,6 +5,7 @@
 #include <mbgl/util/pbf.hpp>
 #include <mbgl/util/vec.hpp>
 #include <mbgl/util/ptr.hpp>
+#include <mbgl/util/uv.hpp>
 
 #include <cstdint>
 #include <vector>
@@ -76,7 +77,7 @@ public:
     // Block until all specified GlyphRanges of the specified font stack are loaded.
     void waitForGlyphRanges(const std::string &fontStack, const std::set<GlyphRange> &glyphRanges);
 
-    FontStack &getFontStack(const std::string &fontStack);
+    uv::exclusive<FontStack> getFontStack(const std::string &fontStack);
 
     void setURL(const std::string &url);
 
@@ -90,7 +91,7 @@ private:
     FileSource& fileSource;
     std::unordered_map<std::string, std::map<GlyphRange, std::unique_ptr<GlyphPBF>>> ranges;
     std::unordered_map<std::string, std::unique_ptr<FontStack>> stacks;
-    std::mutex mtx;
+    std::unique_ptr<uv::mutex> mtx;
 };