1 /*

     2  * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #ifndef SHARE_VM_RUNTIME_SAFEPOINT_HPP

    26 #define SHARE_VM_RUNTIME_SAFEPOINT_HPP

    27 

    28 #include "asm/assembler.hpp"

    29 #include "code/nmethod.hpp"

    30 #include "memory/allocation.hpp"

    31 #include "runtime/extendedPC.hpp"

    32 #include "runtime/mutexLocker.hpp"

    33 #include "runtime/os.hpp"

    34 #include "utilities/ostream.hpp"

    35 

    36 //

    37 // Safepoint synchronization

    38 ////

    39 // The VMThread or CMS_thread uses the SafepointSynchronize::begin/end

    40 // methods to enter/exit a safepoint region. The begin method will roll

    41 // all JavaThreads forward to a safepoint.

    42 //

    43 // JavaThreads must use the ThreadSafepointState abstraction (defined in

    44 // thread.hpp) to indicate that that they are at a safepoint.

    45 //

    46 // The Mutex/Condition variable and ObjectLocker classes calls the enter/

    47 // exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/

    48 // exit points *must* be at a safepoint.

    49 

    50 

    51 class ThreadSafepointState;

    52 class SnippetCache;

    53 class nmethod;

    54 

    55 //

    56 // Implements roll-forward to safepoint (safepoint synchronization)

    57 //

    58 class SafepointSynchronize : AllStatic {

    59  public:

    60   enum SynchronizeState {

    61       _not_synchronized = 0,                   // Threads not synchronized at a safepoint

    62                                                // Keep this value 0. See the comment in do_call_back()

    63       _synchronizing    = 1,                   // Synchronizing in progress

    64       _synchronized     = 2                    // All Java threads are stopped at a safepoint. Only VM thread is running

    65   };

    66 

    67   enum SafepointingThread {

    68       _null_thread  = 0,

    69       _vm_thread    = 1,

    70       _other_thread = 2

    71   };

    72 

    73   enum SafepointTimeoutReason {

    74     _spinning_timeout = 0,

    75     _blocking_timeout = 1

    76   };

    77 

    78   // The enums are listed in the order of the tasks when done serially.

    79   enum SafepointCleanupTasks {

    80     SAFEPOINT_CLEANUP_DEFLATE_MONITORS,

    81     SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES,

    82     SAFEPOINT_CLEANUP_COMPILATION_POLICY,

    83     SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH,

    84     SAFEPOINT_CLEANUP_STRING_TABLE_REHASH,

    85     SAFEPOINT_CLEANUP_CLD_PURGE,

    86     // Leave this one last.

    87     SAFEPOINT_CLEANUP_NUM_TASKS

    88   };

    89 

    90   typedef struct {

    91     float  _time_stamp;                        // record when the current safepoint occurs in seconds

    92     int    _vmop_type;                         // type of VM operation triggers the safepoint

    93     int    _nof_total_threads;                 // total number of Java threads

    94     int    _nof_initial_running_threads;       // total number of initially seen running threads

    95     int    _nof_threads_wait_to_block;         // total number of threads waiting for to block

    96     bool   _page_armed;                        // true if polling page is armed, false otherwise

    97     int    _nof_threads_hit_page_trap;         // total number of threads hitting the page trap

    98     jlong  _time_to_spin;                      // total time in millis spent in spinning

    99     jlong  _time_to_wait_to_block;             // total time in millis spent in waiting for to block

   100     jlong  _time_to_do_cleanups;               // total time in millis spent in performing cleanups

   101     jlong  _time_to_sync;                      // total time in millis spent in getting to _synchronized

   102     jlong  _time_to_exec_vmop;                 // total time in millis spent in vm operation itself

   103   } SafepointStats;

   104 

   105  private:

   106   static volatile SynchronizeState _state;     // Threads might read this flag directly, without acquiring the Threads_lock

   107   static volatile int _waiting_to_block;       // number of threads we are waiting for to block

   108   static int _current_jni_active_count;        // Counts the number of active critical natives during the safepoint

   109 

   110   // This counter is used for fast versions of jni_Get<Primitive>Field.

   111   // An even value means there is no ongoing safepoint operations.

   112   // The counter is incremented ONLY at the beginning and end of each

   113   // safepoint. The fact that Threads_lock is held throughout each pair of

   114   // increments (at the beginning and end of each safepoint) guarantees

   115   // race freedom.

   116 public:

   117   static volatile int _safepoint_counter;

   118 private:

   119   static long       _end_of_last_safepoint;     // Time of last safepoint in milliseconds

   120 

   121   // Statistics

   122   static jlong            _safepoint_begin_time;     // time when safepoint begins

   123   static SafepointStats*  _safepoint_stats;          // array of SafepointStats struct

   124   static int              _cur_stat_index;           // current index to the above array

   125   static julong           _safepoint_reasons[];      // safepoint count for each VM op

   126   static julong           _coalesced_vmop_count;     // coalesced vmop count

   127   static jlong            _max_sync_time;            // maximum sync time in nanos

   128   static jlong            _max_vmop_time;            // maximum vm operation time in nanos

   129   static float            _ts_of_current_safepoint;  // time stamp of current safepoint in seconds

   130 

   131   static void begin_statistics(int nof_threads, int nof_running);

   132   static void update_statistics_on_spin_end();

   133   static void update_statistics_on_sync_end(jlong end_time);

   134   static void update_statistics_on_cleanup_end(jlong end_time);

   135   static void end_statistics(jlong end_time);

   136   static void print_statistics();

   137   inline static void inc_page_trap_count() {

   138     Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap);

   139   }

   140 

   141   // For debug long safepoint

   142   static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason);

   143 

   144 public:

   145 

   146   // Main entry points

   147 

   148   // Roll all threads forward to safepoint. Must be called by the

   149   // VMThread or CMS_thread.

   150   static void begin();

   151   static void end();                    // Start all suspended threads again...

   152 

   153   static bool safepoint_safe(JavaThread *thread, JavaThreadState state);

   154 

   155   static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state);

   156 

   157   // Query

   158   inline static bool is_at_safepoint()   { return _state == _synchronized;  }

   159   inline static bool is_synchronizing()  { return _state == _synchronizing;  }

   160   inline static int safepoint_counter()  { return _safepoint_counter; }

   161 

   162   inline static bool do_call_back() {

   163     return (_state != _not_synchronized);

   164   }

   165 

   166   inline static void increment_jni_active_count() {

   167     assert_locked_or_safepoint(Safepoint_lock);

   168     _current_jni_active_count++;

   169   }

   170 

   171   // Called when a thread voluntarily blocks

   172   static void   block(JavaThread *thread);

   173   static void   signal_thread_at_safepoint()              { _waiting_to_block--; }

   174 

   175   // Exception handling for page polling

   176   static void handle_polling_page_exception(JavaThread *thread);

   177 

   178   // VM Thread interface for determining safepoint rate

   179   static long last_non_safepoint_interval() {

   180     return os::javaTimeMillis() - _end_of_last_safepoint;

   181   }

   182   static long end_of_last_safepoint() {

   183     return _end_of_last_safepoint;

   184   }

   185   static bool is_cleanup_needed();

   186   static void do_cleanup_tasks();

   187 

   188   // Debugging

   189   static void print_state()                                PRODUCT_RETURN;

   190   static void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(1, 2) PRODUCT_RETURN;

   191 

   192   static void deferred_initialize_stat();

   193   static void print_stat_on_exit();

   194   inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; }

   195 

   196   static void set_is_at_safepoint()                        { _state = _synchronized; }

   197   static void set_is_not_at_safepoint()                    { _state = _not_synchronized; }

   198 

   199   // Assembly support

   200   static address address_of_state()                        { return (address)&_state; }

   201 

   202   static address safepoint_counter_addr()                  { return (address)&_safepoint_counter; }

   203 };

   204 

   205 // State class for a thread suspended at a safepoint

   206 class ThreadSafepointState: public CHeapObj<mtInternal> {

   207  public:

   208   // These states are maintained by VM thread while threads are being brought

   209   // to a safepoint.  After SafepointSynchronize::end(), they are reset to

   210   // _running.

   211   enum suspend_type {

   212     _running                =  0, // Thread state not yet determined (i.e., not at a safepoint yet)

   213     _at_safepoint           =  1, // Thread at a safepoint (f.ex., when blocked on a lock)

   214     _call_back              =  2  // Keep executing and wait for callback (if thread is in interpreted or vm)

   215   };

   216  private:

   217   volatile bool _at_poll_safepoint;  // At polling page safepoint (NOT a poll return safepoint)

   218   // Thread has called back the safepoint code (for debugging)

   219   bool                           _has_called_back;

   220 

   221   JavaThread *                   _thread;

   222   volatile suspend_type          _type;

   223   JavaThreadState                _orig_thread_state;

   224 

   225 

   226  public:

   227   ThreadSafepointState(JavaThread *thread);

   228 

   229   // examine/roll-forward/restart

   230   void examine_state_of_thread();

   231   void roll_forward(suspend_type type);

   232   void restart();

   233 

   234   // Query

   235   JavaThread*  thread() const         { return _thread; }

   236   suspend_type type() const           { return _type; }

   237   bool         is_running() const     { return (_type==_running); }

   238   JavaThreadState orig_thread_state() const { return _orig_thread_state; }

   239 

   240   // Support for safepoint timeout (debugging)

   241   bool has_called_back() const                   { return _has_called_back; }

   242   void set_has_called_back(bool val)             { _has_called_back = val; }

   243   bool              is_at_poll_safepoint() { return _at_poll_safepoint; }

   244   void              set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; }

   245 

   246   void handle_polling_page_exception();

   247 

   248   // debugging

   249   void print_on(outputStream* st) const;

   250   void print() const                        { print_on(tty); }

   251 

   252   // Initialize

   253   static void create(JavaThread *thread);

   254   static void destroy(JavaThread *thread);

   255 

   256   void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(2, 3) {

   257     if (ShowSafepointMsgs) {

   258       va_list ap;

   259       va_start(ap, format);

   260       tty->vprint_cr(format, ap);

   261       va_end(ap);

   262     }

   263   }

   264 };

   265 

   266 

   267 

   268 #endif // SHARE_VM_RUNTIME_SAFEPOINT_HPP