[wasm] Initial signal handler

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 38a26be1e29a70450d6d08460fbe0e7473b25244..bd5aadb72265384515bf732be9adf39791767476 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -1201,6 +1201,10 @@ Object* Isolate::UnwindAndFindHandler() {
   for (StackFrameIterator iter(this); !iter.done(); iter.Advance()) {
     StackFrame* frame = iter.frame();
 
+    if (frame->is_wasm()) {
+      trap_handler::ClearThreadInWasm();

[Mark Seaborn, 2017/02/17 21:41:12]

The other calls are guarded by "if (trap_handler::ShouldEnableTrapHandler())"

Maybe that guard should go into trap_handler::Set/ClearThreadInWasm()?

[ahaas, 2017/02/20 09:27:24]

Is it intentional that ClearThreadInWasm is called multiple times here?

[titzer, 2017/02/20 09:50:08]

+1 and make the method inline

[Eric Holk, 2017/02/23 02:16:55]

Originally, it didn't really matter either way since ClearThreadInWasm was
idempotent. Just calling ClearThreadInWasm is probably cheaper than determining
whether to call it.

However, I made Set/ClearThreadInWasm DCHECK the correct state first, so now we
can't call them multiple times. I've added IsThreadInWasm() to the if condition
here.

[Eric Holk, 2017/02/23 02:16:55]

Done.

[Eric Holk, 2017/02/23 02:16:56]

Done.

+    }
+
     // For JSEntryStub frames we always have a handler.
     if (frame->is_entry() || frame->is_entry_construct()) {
       StackHandler* handler = frame->top_handler();
@@ -1232,6 +1236,13 @@ Object* Isolate::UnwindAndFindHandler() {
 
           handler_sp = return_sp;
           handler_fp = frame->fp();
+
+          // This is going to be handled by Wasm, so we need to set the TLS flag
+          // again.
+          if (trap_handler::ShouldEnableTrapHandler()) {
+            trap_handler::SetThreadInWasm();
+          }
+
           break;
         }
       }