Add/reorganize locks for thread synchronization (#1995)

Attempt to fix data races when using threads.
- Protect access (from multiple threads) to exception and memory
- Fix shared memory lock usage

core/iwasm/interpreter/wasm_runtime.h

@@ -19,6 +19,8 @@
 extern "C" {
 #endif
 
+#define EXCEPTION_BUF_LEN 128
+
 typedef struct WASMModuleInstance WASMModuleInstance;
 typedef struct WASMFunctionInstance WASMFunctionInstance;
 typedef struct WASMMemoryInstance WASMMemoryInstance;
@@ -282,7 +284,7 @@ struct WASMModuleInstance {
     DefPointer(WASMExportTabInstance *, export_tables);
 
     /* The exception buffer of wasm interpreter for current thread. */
-    char cur_exception[128];
+    char cur_exception[EXCEPTION_BUF_LEN];
 
     /* The WASM module or AOT module, for AOTModuleInstance,
        it denotes `AOTModule *` */
@@ -444,6 +446,15 @@ wasm_set_exception_with_id(WASMModuleInstance *module_inst, uint32 id);
 const char *
 wasm_get_exception(WASMModuleInstance *module);
 
+/**
+ * @brief Copy exception in buffer passed as parameter. Thread-safe version of
+ * `wasm_get_exception()`
+ * @note Buffer size must be no smaller than EXCEPTION_BUF_LEN
+ * @return true if exception found
+ */
+bool
+wasm_copy_exception(WASMModuleInstance *module_inst, char *exception_buf);
+
 uint32
 wasm_module_malloc(WASMModuleInstance *module_inst, uint32 size,
                    void **p_native_addr);