8237750: Load libzip.so only if necessary

Libzip.so is unconditionally loaded even without usage. Fix by on demand loading.

Reviewed-by: dlong, iklam, ccheung

src/hotspot/share/classfile/classLoader.cpp

@@ -95,6 +95,7 @@ static FindEntry_t       FindEntry          = NULL;
 static ReadEntry_t       ReadEntry          = NULL;
 static GetNextEntry_t    GetNextEntry       = NULL;
 static Crc32_t           Crc32              = NULL;
+int ClassLoader::_libzip_loaded = 0;
 
 // Entry points for jimage.dll for loading jimage file entries
 
@@ -747,6 +748,7 @@ ClassPathEntry* ClassLoader::create_class_path_entry(const char *path, const str
         // enable call to C land
         ThreadToNativeFromVM ttn(thread);
         HandleMark hm(thread);
+        load_zip_library_if_needed();
         zip = (*ZipOpen)(canonical_path, &error_msg);
       }
       if (zip != NULL && error_msg == NULL) {
@@ -796,6 +798,7 @@ ClassPathZipEntry* ClassLoader::create_class_path_zip_entry(const char *path, bo
           JavaThread* thread = JavaThread::current();
           ThreadToNativeFromVM ttn(thread);
           HandleMark hm(thread);
+          load_zip_library_if_needed();
           zip = (*ZipOpen)(canonical_path, &error_msg);
         }
         if (zip != NULL && error_msg == NULL) {
@@ -967,6 +970,14 @@ void ClassLoader::load_java_library() {
   CanonicalizeEntry = CAST_TO_FN_PTR(canonicalize_fn_t, dll_lookup(javalib_handle, "JDK_Canonicalize", NULL));
 }
 
+void ClassLoader::release_load_zip_library() {
+  MutexLocker locker(Zip_lock, Monitor::_no_safepoint_check_flag);
+  if (_libzip_loaded == 0) {
+    load_zip_library();
+    Atomic::release_store(&_libzip_loaded, 1);
+  }
+}
+
 void ClassLoader::load_zip_library() {
   assert(ZipOpen == NULL, "should not load zip library twice");
   char path[JVM_MAXPATHLEN];
@@ -1008,6 +1019,7 @@ void ClassLoader::load_jimage_library() {
 }
 
 int ClassLoader::crc32(int crc, const char* buf, int len) {
+  load_zip_library_if_needed();
   return (*Crc32)(crc, (const jbyte*)buf, len);
 }
 
@@ -1466,8 +1478,6 @@ void ClassLoader::initialize() {
 
   // lookup java library entry points
   load_java_library();
-  // lookup zip library entry points
-  load_zip_library();
   // jimage library entry points are loaded below, in lookup_vm_options
   setup_bootstrap_search_path();
 }

src/hotspot/share/classfile/classLoader.hpp

@@ -252,6 +252,11 @@ class ClassLoader: AllStatic {
   static void load_zip_library();
   static void load_jimage_library();
 
+ private:
+  static int  _libzip_loaded; // used to sync loading zip.
+  static void release_load_zip_library();
+  static inline void load_zip_library_if_needed();
+
  public:
   static ClassPathEntry* create_class_path_entry(const char *path, const struct stat* st,
                                                  bool throw_exception,

src/hotspot/share/classfile/classLoader.inline.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -56,6 +56,12 @@ inline ClassPathEntry* ClassLoader::classpath_entry(int n) {
   }
 }
 
+inline void ClassLoader::load_zip_library_if_needed() {
+  if (Atomic::load_acquire(&_libzip_loaded) == 0) {
+    release_load_zip_library();
+  }
+}
+
 #if INCLUDE_CDS
 
 // Helper function used by CDS code to get the number of boot classpath

src/hotspot/share/runtime/mutexLocker.cpp

@@ -120,6 +120,7 @@ Monitor* Notification_lock            = NULL;
 Monitor* PeriodicTask_lock            = NULL;
 Monitor* RedefineClasses_lock         = NULL;
 Mutex*   Verify_lock                  = NULL;
+Monitor* Zip_lock                     = NULL;
 
 #if INCLUDE_JFR
 Mutex*   JfrStacktrace_lock           = NULL;
@@ -309,6 +310,7 @@ void mutex_init() {
   def(PeriodicTask_lock            , PaddedMonitor, nonleaf+5,   true,  _safepoint_check_always);
   def(RedefineClasses_lock         , PaddedMonitor, nonleaf+5,   true,  _safepoint_check_always);
   def(Verify_lock                  , PaddedMutex,   nonleaf+5,   true,  _safepoint_check_always);
+  def(Zip_lock                     , PaddedMonitor, leaf,        true,  _safepoint_check_never);
 
   if (WhiteBoxAPI) {
     def(Compilation_lock           , PaddedMonitor, leaf,        false, _safepoint_check_never);

src/hotspot/share/runtime/mutexLocker.hpp

@@ -115,6 +115,7 @@ extern Monitor* Notification_lock;               // a lock used for notification
 extern Monitor* PeriodicTask_lock;               // protects the periodic task structure
 extern Monitor* RedefineClasses_lock;            // locks classes from parallel redefinition
 extern Mutex*   Verify_lock;                     // synchronize initialization of verify library
+extern Monitor* Zip_lock;                        // synchronize initialization of zip library
 extern Monitor* ThreadsSMRDelete_lock;           // Used by ThreadsSMRSupport to take pressure off the Threads_lock
 extern Mutex*   ThreadIdTableCreate_lock;        // Used by ThreadIdTable to lazily create the thread id table
 extern Mutex*   SharedDecoder_lock;              // serializes access to the decoder during normal (not error reporting) use

test/hotspot/jtreg/serviceability/sa/ClhsdbPmap.java

@@ -57,7 +57,7 @@ public static void main(String[] args) throws Exception {
                     List.of("Not available on Mac OS X"));
             } else {
                 expStrMap.put("pmap",
-                    List.of("jvm", "java", "net", "nio", "jimage", "zip"));
+                    List.of("jvm", "java", "net", "nio", "jimage"));
             }
 
             test.run(theApp.getPid(), cmds, expStrMap, null);