Function parallelism (#343)

* allow traversals to mark themselves as function-parallel, in which case we run them using a thread pool. also mark some thread-safety risks (interned strings, arena allocators) with assertions they modify only on the main thread

1 files changed, 7 insertions, 0 deletions

diff --git a/src/mixed_arena.h b/src/mixed_arena.h
index 82464d51e..dc8cbad5b 100644
--- a/src/mixed_arena.h
+++ b/src/mixed_arena.h
@@ -19,6 +19,8 @@
 
 #include <vector>
 
+#include "support/threads.h"
+
 //
 // Arena allocation for mixed-type data.
 //
@@ -29,6 +31,9 @@ struct MixedArena {
 
   template<class T>
   T* alloc() {
+    // this structure should not be modified by multiple threads at once.
+    assert(!wasm::ThreadPool::isRunning());
+
     const size_t CHUNK = 10000;
     size_t currSize = (sizeof(T) + 7) & (-8); // same alignment as malloc TODO optimize?
     assert(currSize < CHUNK);
@@ -43,6 +48,8 @@ struct MixedArena {
   }
 
   void clear() {
+    assert(!wasm::ThreadPool::isRunning());
+
     for (char* chunk : chunks) {
       delete[] chunk;
     }