src/hotspot/share/code/nmethod.cpp

rev 54589 : 8219586: CodeHeap State Analytics processes dead nmethods
Reviewed-by:

*** 843,852 ****
--- 843,870 ----
  }
  
  #undef LOG_OFFSET
  
  
+ // Iterating over all nmethods, e.g. with the help of CodeCache::nmethods_do(fun) was found
+ // to not be inherently safe. There is a chance that fields are seen which are not properly
+ // initialized. This happens despite the fact that nmethods_do() asserts the CodeCache_lock
+ // to be held.
+ // To bundle knowledge about necessary checks in one place, this function was introduced.
+ // It is not claimed that these checks are sufficient, but they were found to be necessary.
+ bool nmethod::access_is_safe(nmethod* nm) {
+   Method* method = (nm == NULL) ? NULL : nm->method();  // nm->method() may be uninitialized, i.e. != NULL, but invalid
+   return (nm != NULL) && (method != NULL) &&
+          nm->is_alive() && !nm->is_not_installed() &&
+          os::is_readable_pointer(method) &&
+          os::is_readable_pointer(method->constMethod()) &&
+          os::is_readable_pointer(method->constants()) &&
+          (method->signature() != NULL) &&
+          os::is_readable_pointer(method->signature());
+ }
+ 
+ 
  // Print out more verbose output usually for a newly created nmethod.
  void nmethod::print_on(outputStream* st, const char* msg) const {
    if (st != NULL) {
      ttyLocker ttyl;
      if (WizardMode) {