/* * Copyright (c) 1997, 2014, 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 * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #ifndef SHARE_VM_RUNTIME_SAFEPOINT_HPP #define SHARE_VM_RUNTIME_SAFEPOINT_HPP #include "asm/assembler.hpp" #include "code/nmethod.hpp" #include "memory/allocation.hpp" #include "runtime/extendedPC.hpp" #include "runtime/mutexLocker.hpp" #include "runtime/os.hpp" #include "utilities/ostream.hpp" // // Safepoint synchronization //// // The VMThread or CMS_thread uses the SafepointSynchronize::begin/end // methods to enter/exit a safepoint region. The begin method will roll // all JavaThreads forward to a safepoint. // // JavaThreads must use the ThreadSafepointState abstraction (defined in // thread.hpp) to indicate that that they are at a safepoint. // // The Mutex/Condition variable and ObjectLocker classes calls the enter/ // exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/ // exit points *must* be at a safepoint. class ThreadSafepointState; class SnippetCache; class nmethod; // // Implements roll-forward to safepoint (safepoint synchronization) // class SafepointSynchronize : AllStatic { public: enum SynchronizeState { _not_synchronized = 0, // Threads not synchronized at a safepoint // Keep this value 0. See the comment in do_call_back() _synchronizing = 1, // Synchronizing in progress _synchronized = 2 // All Java threads are stopped at a safepoint. Only VM thread is running }; enum SafepointingThread { _null_thread = 0, _vm_thread = 1, _other_thread = 2 }; enum SafepointTimeoutReason { _spinning_timeout = 0, _blocking_timeout = 1 }; enum SafepointCleanupTasks { SAFEPOINT_CLEANUP_DEFLATE_MONITORS, SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES, SAFEPOINT_CLEANUP_COMPILATION_POLICY, SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH, SAFEPOINT_CLEANUP_STRING_TABLE_REHASH, SAFEPOINT_CLEANUP_CLD_PURGE, // Leave this one last. SAFEPOINT_CLEANUP_NUM_TASKS }; typedef struct { float _time_stamp; // record when the current safepoint occurs in seconds int _vmop_type; // type of VM operation triggers the safepoint int _nof_total_threads; // total number of Java threads int _nof_initial_running_threads; // total number of initially seen running threads int _nof_threads_wait_to_block; // total number of threads waiting for to block bool _page_armed; // true if polling page is armed, false otherwise int _nof_threads_hit_page_trap; // total number of threads hitting the page trap jlong _time_to_spin; // total time in millis spent in spinning jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block jlong _time_to_do_cleanups; // total time in millis spent in performing cleanups jlong _time_to_sync; // total time in millis spent in getting to _synchronized jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself } SafepointStats; private: static volatile SynchronizeState _state; // Threads might read this flag directly, without acquiring the Threads_lock static volatile int _waiting_to_block; // number of threads we are waiting for to block static int _current_jni_active_count; // Counts the number of active critical natives during the safepoint // This counter is used for fast versions of jni_GetField. // An even value means there is no ongoing safepoint operations. // The counter is incremented ONLY at the beginning and end of each // safepoint. The fact that Threads_lock is held throughout each pair of // increments (at the beginning and end of each safepoint) guarantees // race freedom. public: static volatile int _safepoint_counter; private: static long _end_of_last_safepoint; // Time of last safepoint in milliseconds // Statistics static jlong _safepoint_begin_time; // time when safepoint begins static SafepointStats* _safepoint_stats; // array of SafepointStats struct static int _cur_stat_index; // current index to the above array static julong _safepoint_reasons[]; // safepoint count for each VM op static julong _coalesced_vmop_count; // coalesced vmop count static jlong _max_sync_time; // maximum sync time in nanos static jlong _max_vmop_time; // maximum vm operation time in nanos static float _ts_of_current_safepoint; // time stamp of current safepoint in seconds static void begin_statistics(int nof_threads, int nof_running); static void update_statistics_on_spin_end(); static void update_statistics_on_sync_end(jlong end_time); static void update_statistics_on_cleanup_end(jlong end_time); static void end_statistics(jlong end_time); static void print_statistics(); inline static void inc_page_trap_count() { Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap); } // For debug long safepoint static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason); public: // Main entry points // Roll all threads forward to safepoint. Must be called by the // VMThread or CMS_thread. static void begin(); static void end(); // Start all suspended threads again... static bool safepoint_safe(JavaThread *thread, JavaThreadState state); static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state); // Query inline static bool is_at_safepoint() { return _state == _synchronized; } inline static bool is_synchronizing() { return _state == _synchronizing; } inline static int safepoint_counter() { return _safepoint_counter; } inline static bool do_call_back() { return (_state != _not_synchronized); } inline static void increment_jni_active_count() { assert_locked_or_safepoint(Safepoint_lock); _current_jni_active_count++; } // Called when a thread voluntarily blocks static void block(JavaThread *thread); static void signal_thread_at_safepoint() { _waiting_to_block--; } // Exception handling for page polling static void handle_polling_page_exception(JavaThread *thread); // VM Thread interface for determining safepoint rate static long last_non_safepoint_interval() { return os::javaTimeMillis() - _end_of_last_safepoint; } static long end_of_last_safepoint() { return _end_of_last_safepoint; } static bool is_cleanup_needed(); static void do_cleanup_tasks(); // Debugging static void print_state() PRODUCT_RETURN; static void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(1, 2) PRODUCT_RETURN; static void deferred_initialize_stat(); static void print_stat_on_exit(); inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; } static void set_is_at_safepoint() { _state = _synchronized; } static void set_is_not_at_safepoint() { _state = _not_synchronized; } // Assembly support static address address_of_state() { return (address)&_state; } static address safepoint_counter_addr() { return (address)&_safepoint_counter; } }; // State class for a thread suspended at a safepoint class ThreadSafepointState: public CHeapObj { public: // These states are maintained by VM thread while threads are being brought // to a safepoint. After SafepointSynchronize::end(), they are reset to // _running. enum suspend_type { _running = 0, // Thread state not yet determined (i.e., not at a safepoint yet) _at_safepoint = 1, // Thread at a safepoint (f.ex., when blocked on a lock) _call_back = 2 // Keep executing and wait for callback (if thread is in interpreted or vm) }; private: volatile bool _at_poll_safepoint; // At polling page safepoint (NOT a poll return safepoint) // Thread has called back the safepoint code (for debugging) bool _has_called_back; JavaThread * _thread; volatile suspend_type _type; JavaThreadState _orig_thread_state; public: ThreadSafepointState(JavaThread *thread); // examine/roll-forward/restart void examine_state_of_thread(); void roll_forward(suspend_type type); void restart(); // Query JavaThread* thread() const { return _thread; } suspend_type type() const { return _type; } bool is_running() const { return (_type==_running); } JavaThreadState orig_thread_state() const { return _orig_thread_state; } // Support for safepoint timeout (debugging) bool has_called_back() const { return _has_called_back; } void set_has_called_back(bool val) { _has_called_back = val; } bool is_at_poll_safepoint() { return _at_poll_safepoint; } void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; } void handle_polling_page_exception(); // debugging void print_on(outputStream* st) const; void print() const { print_on(tty); } // Initialize static void create(JavaThread *thread); static void destroy(JavaThread *thread); void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(2, 3) { if (ShowSafepointMsgs) { va_list ap; va_start(ap, format); tty->vprint_cr(format, ap); va_end(ap); } } }; #endif // SHARE_VM_RUNTIME_SAFEPOINT_HPP