8025856: Fix typos in the GC code
Summary: Fix about 440 typos in comments in the VM code
Reviewed-by: mgerdin, tschatzl, coleenp, kmo, jcoomes
/*
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#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
};
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_Get<Primitive>Field.
// 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 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, ...) 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<mtInternal> {
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, ...) {
if (ShowSafepointMsgs) {
va_list ap;
va_start(ap, format);
tty->vprint_cr(format, ap);
va_end(ap);
}
}
};
#endif // SHARE_VM_RUNTIME_SAFEPOINT_HPP