1 /*
   2  * Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_RUNTIME_SAFEPOINTMECHANISM_HPP
  26 #define SHARE_RUNTIME_SAFEPOINTMECHANISM_HPP
  27 
  28 #include "runtime/globals.hpp"
  29 #include "utilities/globalDefinitions.hpp"
  30 #include "utilities/macros.hpp"
  31 #include "utilities/sizes.hpp"
  32 
  33 // This is the abstracted interface for the safepoint implementation
  34 class SafepointMechanism : public AllStatic {
  35   enum PollingType {
  36     _global_page_poll,
  37     _thread_local_poll
  38   };
  39   static PollingType _polling_type;
  40   static void* _poll_armed_value;
  41   static void* _poll_disarmed_value;
  42   static void set_uses_thread_local_poll()            { _polling_type     = _thread_local_poll; }
  43 
  44   static void* poll_armed_value()                     { return _poll_armed_value; }
  45   static void* poll_disarmed_value()                  { return _poll_disarmed_value; }
  46 
  47   static inline bool local_poll_armed(JavaThread* thread);
  48 
  49   static inline bool local_poll(Thread* thread);
  50   static inline bool global_poll();
  51 
  52   static void block_if_requested_slow(JavaThread *thread);
  53 
  54   static void default_initialize();
  55 
  56   static void pd_initialize() NOT_AIX({ default_initialize(); });
  57 
  58   // By adding 8 to the base address of the protected polling page we can differentiate
  59   // between the armed and disarmed value by masking out this bit.
  60   const static intptr_t _poll_bit = 8;
  61 public:
  62   static intptr_t poll_bit() { return _poll_bit; }
  63 
  64   static bool uses_global_page_poll() { return _polling_type == _global_page_poll; }
  65   static bool uses_thread_local_poll() { return _polling_type == _thread_local_poll; }
  66 
  67   static bool supports_thread_local_poll() {
  68 #ifdef THREAD_LOCAL_POLL
  69     return true;
  70 #else
  71     return false;
  72 #endif
  73   }
  74 
  75   // Call this method to see if this thread should block for a safepoint.
  76   static inline bool should_block(Thread* thread);
  77 
  78   // Blocks a thread until safepoint is completed
  79   static inline void block_if_requested(JavaThread* thread);
  80 
  81   // Caller is responsible for using a memory barrier if needed.
  82   static inline void arm_local_poll(JavaThread* thread);
  83   static inline void disarm_local_poll(JavaThread* thread);
  84 
  85   static inline void arm_local_poll_release(JavaThread* thread);
  86   static inline void disarm_local_poll_release(JavaThread* thread);
  87 
  88   // Setup the selected safepoint mechanism
  89   static void initialize();
  90   static void initialize_header(JavaThread* thread);
  91 };
  92 
  93 #endif // SHARE_RUNTIME_SAFEPOINTMECHANISM_HPP