73 #else
74 #define _LSBINDEX (sizeof(intptr_t)-1)
75 #endif
76
77 class ParkEvent ;
78
79 // See orderAccess.hpp. We assume throughout the VM that mutex lock and
80 // try_lock do fence-lock-acquire, and that unlock does a release-unlock,
81 // *in that order*. If their implementations change such that these
82 // assumptions are violated, a whole lot of code will break.
83
84 // The default length of monitor name is chosen to be 64 to avoid false sharing.
85 static const int MONITOR_NAME_LEN = 64;
86
87 class Monitor : public CHeapObj<mtInternal> {
88
89 public:
90 // A special lock: Is a lock where you are guaranteed not to block while you are
91 // holding it, i.e., no vm operation can happen, taking other locks, etc.
92 // NOTE: It is critical that the rank 'special' be the lowest (earliest)
93 // (except for "event"?) for the deadlock dection to work correctly.
94 // The rank native is only for use in Mutex's created by JVM_RawMonitorCreate,
95 // which being external to the VM are not subject to deadlock detection.
96 // The rank safepoint is used only for synchronization in reaching a
97 // safepoint and leaving a safepoint. It is only used for the Safepoint_lock
98 // currently. While at a safepoint no mutexes of rank safepoint are held
99 // by any thread.
100 // The rank named "leaf" is probably historical (and should
101 // be changed) -- mutexes of this rank aren't really leaf mutexes
102 // at all.
103 enum lock_types {
104 event,
105 special,
106 suspend_resume,
107 leaf = suspend_resume + 2,
108 safepoint = leaf + 10,
109 barrier = safepoint + 1,
110 nonleaf = barrier + 1,
111 max_nonleaf = nonleaf + 900,
112 native = max_nonleaf + 1
113 };
224 debug_only(void set_next(Monitor *next) { _next = next; })
225 #endif
226
227 void set_owner(Thread* owner) {
228 #ifndef PRODUCT
229 set_owner_implementation(owner);
230 debug_only(void verify_Monitor(Thread* thr));
231 #else
232 _owner = owner;
233 #endif
234 }
235
236 };
237
238 // Normally we'd expect Monitor to extend Mutex in the sense that a monitor
239 // constructed from pthreads primitives might extend a mutex by adding
240 // a condvar and some extra metadata. In fact this was the case until J2SE7.
241 //
242 // Currently, however, the base object is a monitor. Monitor contains all the
243 // logic for wait(), notify(), etc. Mutex extends monitor and restricts the
244 // visiblity of wait(), notify(), and notify_all().
245 //
246 // Another viable alternative would have been to have Monitor extend Mutex and
247 // implement all the normal mutex and wait()-notify() logic in Mutex base class.
248 // The wait()-notify() facility would be exposed via special protected member functions
249 // (e.g., _Wait() and _Notify()) in Mutex. Monitor would extend Mutex and expose wait()
250 // as a call to _Wait(). That is, the public wait() would be a wrapper for the protected
251 // _Wait().
252 //
253 // An even better alternative is to simply eliminate Mutex:: and use Monitor:: instead.
254 // After all, monitors are sufficient for Java-level synchronization. At one point in time
255 // there may have been some benefit to having distinct mutexes and monitors, but that time
256 // has past.
257 //
258 // The Mutex/Monitor design parallels that of Java-monitors, being based on
259 // thread-specific park-unpark platform-specific primitives.
260
261
262 class Mutex : public Monitor { // degenerate Monitor
263 public:
264 Mutex (int rank, const char *name, bool allow_vm_block=false);
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73 #else
74 #define _LSBINDEX (sizeof(intptr_t)-1)
75 #endif
76
77 class ParkEvent ;
78
79 // See orderAccess.hpp. We assume throughout the VM that mutex lock and
80 // try_lock do fence-lock-acquire, and that unlock does a release-unlock,
81 // *in that order*. If their implementations change such that these
82 // assumptions are violated, a whole lot of code will break.
83
84 // The default length of monitor name is chosen to be 64 to avoid false sharing.
85 static const int MONITOR_NAME_LEN = 64;
86
87 class Monitor : public CHeapObj<mtInternal> {
88
89 public:
90 // A special lock: Is a lock where you are guaranteed not to block while you are
91 // holding it, i.e., no vm operation can happen, taking other locks, etc.
92 // NOTE: It is critical that the rank 'special' be the lowest (earliest)
93 // (except for "event"?) for the deadlock detection to work correctly.
94 // The rank native is only for use in Mutex's created by JVM_RawMonitorCreate,
95 // which being external to the VM are not subject to deadlock detection.
96 // The rank safepoint is used only for synchronization in reaching a
97 // safepoint and leaving a safepoint. It is only used for the Safepoint_lock
98 // currently. While at a safepoint no mutexes of rank safepoint are held
99 // by any thread.
100 // The rank named "leaf" is probably historical (and should
101 // be changed) -- mutexes of this rank aren't really leaf mutexes
102 // at all.
103 enum lock_types {
104 event,
105 special,
106 suspend_resume,
107 leaf = suspend_resume + 2,
108 safepoint = leaf + 10,
109 barrier = safepoint + 1,
110 nonleaf = barrier + 1,
111 max_nonleaf = nonleaf + 900,
112 native = max_nonleaf + 1
113 };
224 debug_only(void set_next(Monitor *next) { _next = next; })
225 #endif
226
227 void set_owner(Thread* owner) {
228 #ifndef PRODUCT
229 set_owner_implementation(owner);
230 debug_only(void verify_Monitor(Thread* thr));
231 #else
232 _owner = owner;
233 #endif
234 }
235
236 };
237
238 // Normally we'd expect Monitor to extend Mutex in the sense that a monitor
239 // constructed from pthreads primitives might extend a mutex by adding
240 // a condvar and some extra metadata. In fact this was the case until J2SE7.
241 //
242 // Currently, however, the base object is a monitor. Monitor contains all the
243 // logic for wait(), notify(), etc. Mutex extends monitor and restricts the
244 // visibility of wait(), notify(), and notify_all().
245 //
246 // Another viable alternative would have been to have Monitor extend Mutex and
247 // implement all the normal mutex and wait()-notify() logic in Mutex base class.
248 // The wait()-notify() facility would be exposed via special protected member functions
249 // (e.g., _Wait() and _Notify()) in Mutex. Monitor would extend Mutex and expose wait()
250 // as a call to _Wait(). That is, the public wait() would be a wrapper for the protected
251 // _Wait().
252 //
253 // An even better alternative is to simply eliminate Mutex:: and use Monitor:: instead.
254 // After all, monitors are sufficient for Java-level synchronization. At one point in time
255 // there may have been some benefit to having distinct mutexes and monitors, but that time
256 // has past.
257 //
258 // The Mutex/Monitor design parallels that of Java-monitors, being based on
259 // thread-specific park-unpark platform-specific primitives.
260
261
262 class Mutex : public Monitor { // degenerate Monitor
263 public:
264 Mutex (int rank, const char *name, bool allow_vm_block=false);
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