--- old/src/hotspot/share/runtime/safepointMechanism.cpp 2017-12-28 18:15:49.476788000 +0100 +++ new/src/hotspot/share/runtime/safepointMechanism.cpp 2017-12-28 18:15:49.264843000 +0100 @@ -36,23 +36,39 @@ void SafepointMechanism::default_initialize() { if (ThreadLocalHandshakes) { set_uses_thread_local_poll(); - const size_t page_size = os::vm_page_size(); - const size_t allocation_size = 2 * page_size; - char* polling_page = os::reserve_memory(allocation_size, NULL, page_size); - os::commit_memory_or_exit(polling_page, allocation_size, false, "Unable to commit Safepoint polling page"); - - char* bad_page = polling_page; - char* good_page = polling_page + page_size; - - os::protect_memory(bad_page, page_size, os::MEM_PROT_NONE); - os::protect_memory(good_page, page_size, os::MEM_PROT_READ); - - log_info(os)("SafePoint Polling address, bad (protected) page:" INTPTR_FORMAT ", good (unprotected) page:" INTPTR_FORMAT, p2i(bad_page), p2i(good_page)); - os::set_polling_page((address)(bad_page)); - - intptr_t poll_page_val = reinterpret_cast(bad_page); - _poll_armed_value = reinterpret_cast(poll_page_val | poll_bit()); - _poll_disarmed_value = good_page; + + // Poll bit values + intptr_t poll_armed_value = poll_bit(); + intptr_t poll_disarmed_value = 0; + +#ifdef USE_POLL_BIT_ONLY + if (!USE_POLL_BIT_ONLY) +#endif + { + // Polling page + const size_t page_size = os::vm_page_size(); + const size_t allocation_size = 2 * page_size; + char* polling_page = os::reserve_memory(allocation_size, NULL, page_size); + os::commit_memory_or_exit(polling_page, allocation_size, false, "Unable to commit Safepoint polling page"); + + char* bad_page = polling_page; + char* good_page = polling_page + page_size; + + os::protect_memory(bad_page, page_size, os::MEM_PROT_NONE); + os::protect_memory(good_page, page_size, os::MEM_PROT_READ); + + log_info(os)("SafePoint Polling address, bad (protected) page:" INTPTR_FORMAT ", good (unprotected) page:" INTPTR_FORMAT, p2i(bad_page), p2i(good_page)); + os::set_polling_page((address)(bad_page)); + + // Poll address values + intptr_t bad_page_val = reinterpret_cast(bad_page), + good_page_val = reinterpret_cast(good_page); + poll_armed_value |= bad_page_val; + poll_disarmed_value |= good_page_val; + } + + _poll_armed_value = reinterpret_cast(poll_armed_value); + _poll_disarmed_value = reinterpret_cast(poll_disarmed_value); } else { const size_t page_size = os::vm_page_size(); char* polling_page = os::reserve_memory(page_size, NULL, page_size);