1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/runtime/park.hpp Wed Apr 27 01:25:04 2016 +0800
1.3 @@ -0,0 +1,177 @@
1.4 +/*
1.5 + * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.23 + * or visit www.oracle.com if you need additional information or have any
1.24 + * questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#ifndef SHARE_VM_RUNTIME_PARK_HPP
1.29 +#define SHARE_VM_RUNTIME_PARK_HPP
1.30 +
1.31 +#include "utilities/debug.hpp"
1.32 +#include "utilities/globalDefinitions.hpp"
1.33 +/*
1.34 + * Per-thread blocking support for JSR166. See the Java-level
1.35 + * Documentation for rationale. Basically, park acts like wait, unpark
1.36 + * like notify.
1.37 + *
1.38 + * 6271289 --
1.39 + * To avoid errors where an os thread expires but the JavaThread still
1.40 + * exists, Parkers are immortal (type-stable) and are recycled across
1.41 + * new threads. This parallels the ParkEvent implementation.
1.42 + * Because park-unpark allow spurious wakeups it is harmless if an
1.43 + * unpark call unparks a new thread using the old Parker reference.
1.44 + *
1.45 + * In the future we'll want to think about eliminating Parker and using
1.46 + * ParkEvent instead. There's considerable duplication between the two
1.47 + * services.
1.48 + *
1.49 + */
1.50 +
1.51 +class Parker : public os::PlatformParker {
1.52 +private:
1.53 + volatile int _counter ;
1.54 + Parker * FreeNext ;
1.55 + JavaThread * AssociatedWith ; // Current association
1.56 +
1.57 +public:
1.58 + Parker() : PlatformParker() {
1.59 + _counter = 0 ;
1.60 + FreeNext = NULL ;
1.61 + AssociatedWith = NULL ;
1.62 + }
1.63 +protected:
1.64 + ~Parker() { ShouldNotReachHere(); }
1.65 +public:
1.66 + // For simplicity of interface with Java, all forms of park (indefinite,
1.67 + // relative, and absolute) are multiplexed into one call.
1.68 + void park(bool isAbsolute, jlong time);
1.69 + void unpark();
1.70 +
1.71 + // Lifecycle operators
1.72 + static Parker * Allocate (JavaThread * t) ;
1.73 + static void Release (Parker * e) ;
1.74 +private:
1.75 + static Parker * volatile FreeList ;
1.76 + static volatile int ListLock ;
1.77 +
1.78 +};
1.79 +
1.80 +/////////////////////////////////////////////////////////////
1.81 +//
1.82 +// ParkEvents are type-stable and immortal.
1.83 +//
1.84 +// Lifecycle: Once a ParkEvent is associated with a thread that ParkEvent remains
1.85 +// associated with the thread for the thread's entire lifetime - the relationship is
1.86 +// stable. A thread will be associated at most one ParkEvent. When the thread
1.87 +// expires, the ParkEvent moves to the EventFreeList. New threads attempt to allocate from
1.88 +// the EventFreeList before creating a new Event. Type-stability frees us from
1.89 +// worrying about stale Event or Thread references in the objectMonitor subsystem.
1.90 +// (A reference to ParkEvent is always valid, even though the event may no longer be associated
1.91 +// with the desired or expected thread. A key aspect of this design is that the callers of
1.92 +// park, unpark, etc must tolerate stale references and spurious wakeups).
1.93 +//
1.94 +// Only the "associated" thread can block (park) on the ParkEvent, although
1.95 +// any other thread can unpark a reachable parkevent. Park() is allowed to
1.96 +// return spuriously. In fact park-unpark a really just an optimization to
1.97 +// avoid unbounded spinning and surrender the CPU to be a polite system citizen.
1.98 +// A degenerate albeit "impolite" park-unpark implementation could simply return.
1.99 +// See http://blogs.sun.com/dave for more details.
1.100 +//
1.101 +// Eventually I'd like to eliminate Events and ObjectWaiters, both of which serve as
1.102 +// thread proxies, and simply make the THREAD structure type-stable and persistent.
1.103 +// Currently, we unpark events associated with threads, but ideally we'd just
1.104 +// unpark threads.
1.105 +//
1.106 +// The base-class, PlatformEvent, is platform-specific while the ParkEvent is
1.107 +// platform-independent. PlatformEvent provides park(), unpark(), etc., and
1.108 +// is abstract -- that is, a PlatformEvent should never be instantiated except
1.109 +// as part of a ParkEvent.
1.110 +// Equivalently we could have defined a platform-independent base-class that
1.111 +// exported Allocate(), Release(), etc. The platform-specific class would extend
1.112 +// that base-class, adding park(), unpark(), etc.
1.113 +//
1.114 +// A word of caution: The JVM uses 2 very similar constructs:
1.115 +// 1. ParkEvent are used for Java-level "monitor" synchronization.
1.116 +// 2. Parkers are used by JSR166-JUC park-unpark.
1.117 +//
1.118 +// We'll want to eventually merge these redundant facilities and use ParkEvent.
1.119 +
1.120 +
1.121 +class ParkEvent : public os::PlatformEvent {
1.122 + private:
1.123 + ParkEvent * FreeNext ;
1.124 +
1.125 + // Current association
1.126 + Thread * AssociatedWith ;
1.127 + intptr_t RawThreadIdentity ; // LWPID etc
1.128 + volatile int Incarnation ;
1.129 +
1.130 + // diagnostic : keep track of last thread to wake this thread.
1.131 + // this is useful for construction of dependency graphs.
1.132 + void * LastWaker ;
1.133 +
1.134 + public:
1.135 + // MCS-CLH list linkage and Native Mutex/Monitor
1.136 + ParkEvent * volatile ListNext ;
1.137 + ParkEvent * volatile ListPrev ;
1.138 + volatile intptr_t OnList ;
1.139 + volatile int TState ;
1.140 + volatile int Notified ; // for native monitor construct
1.141 + volatile int IsWaiting ; // Enqueued on WaitSet
1.142 +
1.143 +
1.144 + private:
1.145 + static ParkEvent * volatile FreeList ;
1.146 + static volatile int ListLock ;
1.147 +
1.148 + // It's prudent to mark the dtor as "private"
1.149 + // ensuring that it's not visible outside the package.
1.150 + // Unfortunately gcc warns about such usage, so
1.151 + // we revert to the less desirable "protected" visibility.
1.152 + // The other compilers accept private dtors.
1.153 +
1.154 + protected: // Ensure dtor is never invoked
1.155 + ~ParkEvent() { guarantee (0, "invariant") ; }
1.156 +
1.157 + ParkEvent() : PlatformEvent() {
1.158 + AssociatedWith = NULL ;
1.159 + FreeNext = NULL ;
1.160 + ListNext = NULL ;
1.161 + ListPrev = NULL ;
1.162 + OnList = 0 ;
1.163 + TState = 0 ;
1.164 + Notified = 0 ;
1.165 + IsWaiting = 0 ;
1.166 + }
1.167 +
1.168 + // We use placement-new to force ParkEvent instances to be
1.169 + // aligned on 256-byte address boundaries. This ensures that the least
1.170 + // significant byte of a ParkEvent address is always 0.
1.171 +
1.172 + void * operator new (size_t sz) throw();
1.173 + void operator delete (void * a) ;
1.174 +
1.175 + public:
1.176 + static ParkEvent * Allocate (Thread * t) ;
1.177 + static void Release (ParkEvent * e) ;
1.178 +} ;
1.179 +
1.180 +#endif // SHARE_VM_RUNTIME_PARK_HPP
