diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/runtime/safepoint.hpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/hotspot/share/runtime/safepoint.hpp Tue Sep 12 19:03:39 2017 +0200 @@ -0,0 +1,268 @@ +/* + * Copyright (c) 1997, 2017, 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 + }; + + // The enums are listed in the order of the tasks when done serially. + 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