Protect EVM JIT cache with mutex.

Fixes ethereum/cpp-ethereum#2086.

evmjit/libevmjit/Cache.cpp

@@ -1,5 +1,7 @@
 #include "Cache.h"
 
+#include <mutex>
+
 #include "preprocessor/llvm_includes_start.h"
 #include <llvm/IR/Module.h>
 #include <llvm/IR/LLVMContext.h>
@@ -23,6 +25,8 @@ namespace jit
 
 namespace
 {
+	using Guard = std::lock_guard<std::mutex>;
+	std::mutex x_cacheMutex;
 	CacheMode g_mode;
 	llvm::MemoryBuffer* g_lastObject;
 	ExecutionEngineListener* g_listener;
@@ -43,6 +47,9 @@ namespace
 ObjectCache* Cache::getObjectCache(CacheMode _mode, ExecutionEngineListener* _listener)
 {
 	static ObjectCache objectCache;
+
+	Guard g{x_cacheMutex};
+
 	g_mode = _mode;
 	g_listener = _listener;
 	return &objectCache;
@@ -50,6 +57,8 @@ ObjectCache* Cache::getObjectCache(CacheMode _mode, ExecutionEngineListener* _li
 
 void Cache::clear()
 {
+	Guard g{x_cacheMutex};
+
 	using namespace llvm::sys;
 	llvm::SmallString<256> cachePath;
 	path::system_temp_directory(false, cachePath);
@@ -62,6 +71,8 @@ void Cache::clear()
 
 void Cache::preload(llvm::ExecutionEngine& _ee, std::unordered_map<std::string, uint64_t>& _funcCache)
 {
+	Guard g{x_cacheMutex};
+
 	// TODO: Cache dir should be in one place
 	using namespace llvm::sys;
 	llvm::SmallString<256> cachePath;
@@ -92,11 +103,14 @@ void Cache::preload(llvm::ExecutionEngine& _ee, std::unordered_map<std::string,
 
 std::unique_ptr<llvm::Module> Cache::getObject(std::string const& id)
 {
+	Guard g{x_cacheMutex};
+
 	if (g_mode != CacheMode::on && g_mode != CacheMode::read)
 		return nullptr;
 
-	if (g_listener)
-		g_listener->stateChanged(ExecState::CacheLoad);
+	// TODO: Disabled because is not thread-safe.
+	//if (g_listener)
+	//	g_listener->stateChanged(ExecState::CacheLoad);
 
 	DLOG(cache) << id << ": search\n";
 	if (!CHECK(!g_lastObject))
@@ -136,12 +150,15 @@ std::unique_ptr<llvm::Module> Cache::getObject(std::string const& id)
 
 void ObjectCache::notifyObjectCompiled(llvm::Module const* _module, llvm::MemoryBuffer const* _object)
 {
+	Guard g{x_cacheMutex};
+
 	// Only in "on" and "write" mode
 	if (g_mode != CacheMode::on && g_mode != CacheMode::write)
 		return;
 
-	if (g_listener)
-		g_listener->stateChanged(ExecState::CacheWrite);
+	// TODO: Disabled because is not thread-safe.
+	// if (g_listener)
+		// g_listener->stateChanged(ExecState::CacheWrite);
 
 	auto&& id = _module->getModuleIdentifier();
 	llvm::SmallString<256> cachePath;
@@ -161,6 +178,8 @@ void ObjectCache::notifyObjectCompiled(llvm::Module const* _module, llvm::Memory
 
 llvm::MemoryBuffer* ObjectCache::getObject(llvm::Module const* _module)
 {
+	Guard g{x_cacheMutex};
+
 	DLOG(cache) << _module->getModuleIdentifier() << ": use\n";
 	auto o = g_lastObject;
 	g_lastObject = nullptr;