Fix racy global in gl::Compiler.

We introduce a new Display Global Mutex in egl::Display that
can guard access to gActiveCompilers in Compiler.cpp.

Was detected by running MultithreadingTest against TSAN.

Bug: b/168744561
Change-Id: I97866b60a173f60899cd0406fe0f71000035c0cf
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2415181
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>

src/libANGLE/Compiler.cpp

@@ -9,6 +9,8 @@
 #include "libANGLE/Compiler.h"
 
 #include "common/debug.h"
+#include "libANGLE/Context.h"
+#include "libANGLE/Display.h"
 #include "libANGLE/State.h"
 #include "libANGLE/renderer/CompilerImpl.h"
 #include "libANGLE/renderer/GLImplFactory.h"
@@ -56,7 +58,7 @@ ShShaderSpec SelectShaderSpec(GLint majorVersion,
 
 }  // anonymous namespace
 
-Compiler::Compiler(rx::GLImplFactory *implFactory, const State &state)
+Compiler::Compiler(rx::GLImplFactory *implFactory, const State &state, egl::Display *display)
     : mImplementation(implFactory->createCompiler()),
       mSpec(SelectShaderSpec(state.getClientMajorVersion(),
                              state.getClientMinorVersion(),
@@ -72,11 +74,14 @@ Compiler::Compiler(rx::GLImplFactory *implFactory, const State &state)
     const gl::Caps &caps             = state.getCaps();
     const gl::Extensions &extensions = state.getExtensions();
 
-    if (gActiveCompilers == 0)
     {
-        sh::Initialize();
+        std::lock_guard<std::mutex> lock(display->getDisplayGlobalMutex());
+        if (gActiveCompilers == 0)
+        {
+            sh::Initialize();
+        }
+        ++gActiveCompilers;
     }
-    ++gActiveCompilers;
 
     sh::InitBuiltInResources(&mResources);
     mResources.MaxVertexAttribs             = caps.maxVertexAttributes;
@@ -211,8 +216,11 @@ Compiler::Compiler(rx::GLImplFactory *implFactory, const State &state)
     mResources.SubPixelBits = static_cast<int>(caps.subPixelBits);
 }
 
-Compiler::~Compiler()
+Compiler::~Compiler() = default;
+
+void Compiler::onDestroy(const Context *context)
 {
+    std::lock_guard<std::mutex> lock(context->getDisplay()->getDisplayGlobalMutex());
     for (auto &pool : mPools)
     {
         for (ShCompilerInstance &instance : pool)

src/libANGLE/Compiler.h

@@ -31,7 +31,9 @@ class State;
 class Compiler final : public RefCountObjectNoID
 {
   public:
-    Compiler(rx::GLImplFactory *implFactory, const State &data);
+    Compiler(rx::GLImplFactory *implFactory, const State &data, egl::Display *display);
+
+    void onDestroy(const Context *context) override;
 
     ShCompilerInstance getInstance(ShaderType shaderType);
     void putInstance(ShCompilerInstance &&instance);

src/libANGLE/Context.cpp

@@ -1367,7 +1367,7 @@ Compiler *Context::getCompiler() const
 {
     if (mCompiler.get() == nullptr)
     {
-        mCompiler.set(this, new Compiler(mImplementation.get(), mState));
+        mCompiler.set(this, new Compiler(mImplementation.get(), mState, mDisplay));
     }
     return mCompiler.get();
 }

src/libANGLE/Display.h

@@ -255,6 +255,8 @@ class Display final : public LabeledObject,
 
     egl::Error handleGPUSwitch();
 
+    std::mutex &getDisplayGlobalMutex() { return mDisplayGlobalMutex; }
+
   private:
     Display(EGLenum platform, EGLNativeDisplayType displayId, Device *eglDevice);
 
@@ -323,6 +325,8 @@ class Display final : public LabeledObject,
     std::mutex mScratchBufferMutex;
     std::vector<angle::ScratchBuffer> mScratchBuffers;
     std::vector<angle::ScratchBuffer> mZeroFilledBuffers;
+
+    std::mutex mDisplayGlobalMutex;
 };
 
 }  // namespace egl