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 #include "precompiled.hpp"
  26 #include "logging/log.hpp"
  27 #include "runtime/globals.hpp"
  28 #include "runtime/os.hpp"
  29 #include "runtime/safepointMechanism.inline.hpp"
  30 #include "services/memTracker.hpp"
  31 #include "utilities/globalDefinitions.hpp"
  32 
  33 SafepointMechanism::PollingType SafepointMechanism::_polling_type = SafepointMechanism::_global_page_poll;
  34 void* SafepointMechanism::_poll_armed_value;
  35 void* SafepointMechanism::_poll_disarmed_value;
  36 
  37 void SafepointMechanism::default_initialize() {
  38   if (ThreadLocalHandshakes) {
  39     set_uses_thread_local_poll();
  40 
  41     // Poll bit values
  42     intptr_t poll_armed_value = poll_bit();
  43     intptr_t poll_disarmed_value = 0;
  44 
  45 #ifdef USE_POLL_BIT_ONLY
  46     if (!USE_POLL_BIT_ONLY)
  47 #endif
  48     {
  49       // Polling page
  50       const size_t page_size = os::vm_page_size();
  51       const size_t allocation_size = 2 * page_size;
  52       char* polling_page = os::reserve_memory(allocation_size, NULL, page_size);
  53       os::commit_memory_or_exit(polling_page, allocation_size, false, "Unable to commit Safepoint polling page");
  54       MemTracker::record_virtual_memory_type((address)polling_page, mtSafepoint);
  55 
  56       char* bad_page  = polling_page;
  57       char* good_page = polling_page + page_size;
  58 
  59       os::protect_memory(bad_page,  page_size, os::MEM_PROT_NONE);
  60       os::protect_memory(good_page, page_size, os::MEM_PROT_READ);
  61 
  62       log_info(os)("SafePoint Polling address, bad (protected) page:" INTPTR_FORMAT ", good (unprotected) page:" INTPTR_FORMAT, p2i(bad_page), p2i(good_page));
  63       os::set_polling_page((address)(bad_page));
  64 
  65       // Poll address values
  66       intptr_t bad_page_val  = reinterpret_cast<intptr_t>(bad_page),
  67                good_page_val = reinterpret_cast<intptr_t>(good_page);
  68       poll_armed_value    |= bad_page_val;
  69       poll_disarmed_value |= good_page_val;
  70     }
  71 
  72     _poll_armed_value    = reinterpret_cast<void*>(poll_armed_value);
  73     _poll_disarmed_value = reinterpret_cast<void*>(poll_disarmed_value);
  74   } else {
  75     const size_t page_size = os::vm_page_size();
  76     char* polling_page = os::reserve_memory(page_size, NULL, page_size);
  77     os::commit_memory_or_exit(polling_page, page_size, false, "Unable to commit Safepoint polling page");
  78     os::protect_memory(polling_page, page_size, os::MEM_PROT_READ);
  79     MemTracker::record_virtual_memory_type((address)polling_page, mtSafepoint);
  80 
  81     log_info(os)("SafePoint Polling address: " INTPTR_FORMAT, p2i(polling_page));
  82     os::set_polling_page((address)(polling_page));
  83   }
  84 }
  85 
  86 void SafepointMechanism::block_or_handshake(JavaThread *thread) {
  87   if (global_poll()) {
  88     // Any load in ::block must not pass the global poll load.
  89     // Otherwise we might load an old safepoint counter (for example).
  90     OrderAccess::loadload();
  91     SafepointSynchronize::block(thread);
  92   }
  93   if (uses_thread_local_poll() && thread->has_handshake()) {
  94     thread->handshake_process_by_self();
  95   }
  96 }
  97 
  98 void SafepointMechanism::block_if_requested_slow(JavaThread *thread) {
  99   // Read global poll and has_handshake after local poll
 100   OrderAccess::loadload();
 101 
 102   // local poll already checked, if used.
 103   block_or_handshake(thread);
 104 
 105   OrderAccess::loadload();
 106 
 107   if (uses_thread_local_poll() && local_poll_armed(thread)) {
 108     disarm_local_poll_release(thread);
 109     // We might have disarmed next safepoint/handshake
 110     OrderAccess::storeload();
 111     if (global_poll() || thread->has_handshake()) {
 112       arm_local_poll(thread);
 113     }
 114   }
 115 
 116   OrderAccess::cross_modify_fence();
 117 }
 118 
 119 void SafepointMechanism::initialize_header(JavaThread* thread) {
 120   disarm_local_poll(thread);
 121 }
 122 
 123 void SafepointMechanism::initialize() {
 124   pd_initialize();
 125 }