8024007: Misc. cleanup of static agent code

Summary: Minor cleanup of static agent code from 8014135
Reviewed-by: dcubed, sspitsyn

src/os/windows/vm/os_windows.cpp

@@ -5429,7 +5429,7 @@ char* os::build_agent_function_name(const char *sym_name, const char *lib_name,
       if ((start = strrchr(lib_name, *os::file_separator())) != NULL) {
         lib_name = ++start;
       } else {
-        // Need to check for C:
+        // Need to check for drive prefix
         if ((start = strchr(lib_name, ':')) != NULL) {
           lib_name = ++start;
         }

src/share/vm/prims/jvmti.xml

@@ -458,8 +458,10 @@
       the same name from being loaded dynamically.
 <p/>
       The VM will invoke the Agent_OnUnload_L function of the agent, if such
-      a function is exported, at the same point during startup as it would
-      have called the dynamic entry point Agent_OnUnLoad.
+      a function is exported, at the same point during VM execution as it would
+      have called the dynamic entry point Agent_OnUnLoad. A statically loaded
+      agent cannot be unloaded. The Agent_OnUnload_L function will still be
+      called to do any other agent shutdown related tasks. 
       If a <i>statically linked</i> agent L exports a function called
       Agent_OnUnLoad_L and a function called Agent_OnUnLoad, the Agent_OnUnLoad
       function will be ignored.

src/share/vm/runtime/arguments.hpp

@@ -144,7 +144,7 @@ public:
   void set_os_lib(void* os_lib)             { _os_lib = os_lib; }
   AgentLibrary* next() const                { return _next; }
   bool is_static_lib() const                { return _is_static_lib; }
-  void set_static_lib(bool static_lib)      { _is_static_lib = static_lib; }
+  void set_static_lib(bool is_static_lib)   { _is_static_lib = is_static_lib; }
   bool valid()                              { return (_state == agent_valid); }
   void set_valid()                          { _state = agent_valid; }
   void set_invalid()                        { _state = agent_invalid; }

src/share/vm/runtime/os.cpp

@@ -454,6 +454,7 @@ void* os::native_java_library() {
  */
 void* os::find_agent_function(AgentLibrary *agent_lib, bool check_lib,
                               const char *syms[], size_t syms_len) {
+  assert(agent_lib != NULL, "sanity check");
   const char *lib_name;
   void *handle = agent_lib->os_lib();
   void *entryName = NULL;
@@ -484,6 +485,7 @@ bool os::find_builtin_agent(AgentLibrary *agent_lib, const char *syms[],
   void *proc_handle;
   void *save_handle;
 
+  assert(agent_lib != NULL, "sanity check");
   if (agent_lib->name() == NULL) {
     return false;
   }
@@ -493,14 +495,13 @@ bool os::find_builtin_agent(AgentLibrary *agent_lib, const char *syms[],
   // We want to look in this process' symbol table.
   agent_lib->set_os_lib(proc_handle);
   ret = find_agent_function(agent_lib, true, syms, syms_len);
-  agent_lib->set_os_lib(save_handle);
   if (ret != NULL) {
     // Found an entry point like Agent_OnLoad_lib_name so we have a static agent
-    agent_lib->set_os_lib(proc_handle);
     agent_lib->set_valid();
     agent_lib->set_static_lib(true);
     return true;
   }
+  agent_lib->set_os_lib(save_handle);
   return false;
 }
 

src/share/vm/runtime/thread.cpp

@@ -3714,7 +3714,7 @@ static OnLoadEntry_t lookup_on_load(AgentLibrary* agent, const char *on_load_sym
     const char *name = agent->name();
     const char *msg = "Could not find agent library ";
 
-    // First check to see if agent is statcally linked into executable
+    // First check to see if agent is statically linked into executable
     if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
       library = agent->os_lib();
     } else if (agent->is_absolute_path()) {