305ec3bd3f
Repaired or selectively disabled offending formats; future-proofed with additional checking Reviewed-by: kvn, jrose, stefank
256 lines
10 KiB
C++
256 lines
10 KiB
C++
/*
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* Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_VM_RUNTIME_SAFEPOINT_HPP
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#define SHARE_VM_RUNTIME_SAFEPOINT_HPP
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#include "asm/assembler.hpp"
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#include "code/nmethod.hpp"
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#include "memory/allocation.hpp"
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#include "runtime/extendedPC.hpp"
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#include "runtime/mutexLocker.hpp"
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#include "runtime/os.hpp"
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#include "utilities/ostream.hpp"
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//
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// Safepoint synchronization
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////
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// The VMThread or CMS_thread uses the SafepointSynchronize::begin/end
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// methods to enter/exit a safepoint region. The begin method will roll
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// all JavaThreads forward to a safepoint.
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//
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// JavaThreads must use the ThreadSafepointState abstraction (defined in
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// thread.hpp) to indicate that that they are at a safepoint.
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//
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// The Mutex/Condition variable and ObjectLocker classes calls the enter/
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// exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/
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// exit points *must* be at a safepoint.
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class ThreadSafepointState;
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class SnippetCache;
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class nmethod;
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//
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// Implements roll-forward to safepoint (safepoint synchronization)
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//
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class SafepointSynchronize : AllStatic {
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public:
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enum SynchronizeState {
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_not_synchronized = 0, // Threads not synchronized at a safepoint
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// Keep this value 0. See the comment in do_call_back()
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_synchronizing = 1, // Synchronizing in progress
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_synchronized = 2 // All Java threads are stopped at a safepoint. Only VM thread is running
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};
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enum SafepointingThread {
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_null_thread = 0,
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_vm_thread = 1,
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_other_thread = 2
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};
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enum SafepointTimeoutReason {
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_spinning_timeout = 0,
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_blocking_timeout = 1
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};
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typedef struct {
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float _time_stamp; // record when the current safepoint occurs in seconds
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int _vmop_type; // type of VM operation triggers the safepoint
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int _nof_total_threads; // total number of Java threads
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int _nof_initial_running_threads; // total number of initially seen running threads
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int _nof_threads_wait_to_block; // total number of threads waiting for to block
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bool _page_armed; // true if polling page is armed, false otherwise
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int _nof_threads_hit_page_trap; // total number of threads hitting the page trap
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jlong _time_to_spin; // total time in millis spent in spinning
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jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block
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jlong _time_to_do_cleanups; // total time in millis spent in performing cleanups
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jlong _time_to_sync; // total time in millis spent in getting to _synchronized
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jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself
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} SafepointStats;
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private:
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static volatile SynchronizeState _state; // Threads might read this flag directly, without acquiring the Threads_lock
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static volatile int _waiting_to_block; // number of threads we are waiting for to block
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static int _current_jni_active_count; // Counts the number of active critical natives during the safepoint
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// This counter is used for fast versions of jni_Get<Primitive>Field.
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// An even value means there is no ongoing safepoint operations.
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// The counter is incremented ONLY at the beginning and end of each
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// safepoint. The fact that Threads_lock is held throughout each pair of
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// increments (at the beginning and end of each safepoint) guarantees
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// race freedom.
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public:
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static volatile int _safepoint_counter;
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private:
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static long _end_of_last_safepoint; // Time of last safepoint in milliseconds
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// Statistics
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static jlong _safepoint_begin_time; // time when safepoint begins
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static SafepointStats* _safepoint_stats; // array of SafepointStats struct
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static int _cur_stat_index; // current index to the above array
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static julong _safepoint_reasons[]; // safepoint count for each VM op
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static julong _coalesced_vmop_count; // coalesced vmop count
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static jlong _max_sync_time; // maximum sync time in nanos
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static jlong _max_vmop_time; // maximum vm operation time in nanos
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static float _ts_of_current_safepoint; // time stamp of current safepoint in seconds
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static void begin_statistics(int nof_threads, int nof_running);
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static void update_statistics_on_spin_end();
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static void update_statistics_on_sync_end(jlong end_time);
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static void update_statistics_on_cleanup_end(jlong end_time);
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static void end_statistics(jlong end_time);
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static void print_statistics();
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inline static void inc_page_trap_count() {
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Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap);
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}
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// For debug long safepoint
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static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason);
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public:
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// Main entry points
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// Roll all threads forward to safepoint. Must be called by the
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// VMThread or CMS_thread.
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static void begin();
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static void end(); // Start all suspended threads again...
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static bool safepoint_safe(JavaThread *thread, JavaThreadState state);
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static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state);
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// Query
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inline static bool is_at_safepoint() { return _state == _synchronized; }
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inline static bool is_synchronizing() { return _state == _synchronizing; }
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inline static bool do_call_back() {
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return (_state != _not_synchronized);
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}
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inline static void increment_jni_active_count() {
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assert_locked_or_safepoint(Safepoint_lock);
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_current_jni_active_count++;
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}
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// Called when a thread voluntarily blocks
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static void block(JavaThread *thread);
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static void signal_thread_at_safepoint() { _waiting_to_block--; }
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// Exception handling for page polling
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static void handle_polling_page_exception(JavaThread *thread);
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// VM Thread interface for determining safepoint rate
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static long last_non_safepoint_interval() {
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return os::javaTimeMillis() - _end_of_last_safepoint;
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}
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static long end_of_last_safepoint() {
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return _end_of_last_safepoint;
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}
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static bool is_cleanup_needed();
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static void do_cleanup_tasks();
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// Debugging
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static void print_state() PRODUCT_RETURN;
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static void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(1, 2) PRODUCT_RETURN;
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static void deferred_initialize_stat();
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static void print_stat_on_exit();
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inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; }
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static void set_is_at_safepoint() { _state = _synchronized; }
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static void set_is_not_at_safepoint() { _state = _not_synchronized; }
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// Assembly support
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static address address_of_state() { return (address)&_state; }
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static address safepoint_counter_addr() { return (address)&_safepoint_counter; }
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};
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// State class for a thread suspended at a safepoint
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class ThreadSafepointState: public CHeapObj<mtInternal> {
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public:
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// These states are maintained by VM thread while threads are being brought
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// to a safepoint. After SafepointSynchronize::end(), they are reset to
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// _running.
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enum suspend_type {
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_running = 0, // Thread state not yet determined (i.e., not at a safepoint yet)
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_at_safepoint = 1, // Thread at a safepoint (f.ex., when blocked on a lock)
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_call_back = 2 // Keep executing and wait for callback (if thread is in interpreted or vm)
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};
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private:
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volatile bool _at_poll_safepoint; // At polling page safepoint (NOT a poll return safepoint)
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// Thread has called back the safepoint code (for debugging)
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bool _has_called_back;
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JavaThread * _thread;
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volatile suspend_type _type;
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JavaThreadState _orig_thread_state;
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public:
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ThreadSafepointState(JavaThread *thread);
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// examine/roll-forward/restart
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void examine_state_of_thread();
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void roll_forward(suspend_type type);
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void restart();
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// Query
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JavaThread* thread() const { return _thread; }
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suspend_type type() const { return _type; }
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bool is_running() const { return (_type==_running); }
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JavaThreadState orig_thread_state() const { return _orig_thread_state; }
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// Support for safepoint timeout (debugging)
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bool has_called_back() const { return _has_called_back; }
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void set_has_called_back(bool val) { _has_called_back = val; }
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bool is_at_poll_safepoint() { return _at_poll_safepoint; }
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void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; }
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void handle_polling_page_exception();
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// debugging
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void print_on(outputStream* st) const;
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void print() const { print_on(tty); }
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// Initialize
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static void create(JavaThread *thread);
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static void destroy(JavaThread *thread);
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void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(2, 3) {
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if (ShowSafepointMsgs) {
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va_list ap;
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va_start(ap, format);
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tty->vprint_cr(format, ap);
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va_end(ap);
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}
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}
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};
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#endif // SHARE_VM_RUNTIME_SAFEPOINT_HPP
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