8047373: Clean the ExceptionCache in one pass

Summary: Also-reviewed-by: kim.barrett@oracle.com
Reviewed-by: jmasa, jwilhelm

src/share/vm/code/nmethod.cpp

@@ -384,26 +384,29 @@ void nmethod::add_exception_cache_entry(ExceptionCache* new_entry) {
   set_exception_cache(new_entry);
 }
 
-void nmethod::remove_from_exception_cache(ExceptionCache* ec) {
+void nmethod::clean_exception_cache(BoolObjectClosure* is_alive) {
   ExceptionCache* prev = NULL;
   ExceptionCache* curr = exception_cache();
-  assert(curr != NULL, "nothing to remove");
-  // find the previous and next entry of ec
-  while (curr != ec) {
-    prev = curr;
-    curr = curr->next();
-    assert(curr != NULL, "ExceptionCache not found");
-  }
-  // now: curr == ec
+
+  while (curr != NULL) {
     ExceptionCache* next = curr->next();
+
+    Klass* ex_klass = curr->exception_type();
+    if (ex_klass != NULL && !ex_klass->is_loader_alive(is_alive)) {
       if (prev == NULL) {
         set_exception_cache(next);
       } else {
         prev->set_next(next);
       }
       delete curr;
-}
+      // prev stays the same.
+    } else {
+      prev = curr;
+    }
 
+    curr = next;
+  }
+}
 
 // public method for accessing the exception cache
 // These are the public access methods.
@@ -1650,15 +1653,7 @@ void nmethod::do_unloading(BoolObjectClosure* is_alive, bool unloading_occurred)
   }
 
   // Exception cache
-  ExceptionCache* ec = exception_cache();
-  while (ec != NULL) {
-    Klass* ex_klass = ec->exception_type();
-    ExceptionCache* next_ec = ec->next();
-    if (ex_klass != NULL && !ex_klass->is_loader_alive(is_alive)) {
-      remove_from_exception_cache(ec);
-    }
-    ec = next_ec;
-  }
+  clean_exception_cache(is_alive);
 
   // If class unloading occurred we first iterate over all inline caches and
   // clear ICs where the cached oop is referring to an unloaded klass or method.

src/share/vm/code/nmethod.hpp

@@ -534,7 +534,7 @@ public:
   void set_exception_cache(ExceptionCache *ec)    { _exception_cache = ec; }
   address handler_for_exception_and_pc(Handle exception, address pc);
   void add_handler_for_exception_and_pc(Handle exception, address pc, address handler);
-  void remove_from_exception_cache(ExceptionCache* ec);
+  void clean_exception_cache(BoolObjectClosure* is_alive);
 
   // implicit exceptions support
   address continuation_for_implicit_exception(address pc);