Mercurial > hg > truffle
diff src/share/vm/runtime/thread.hpp @ 1878:fa83ab460c54
6988353: refactor contended sync subsystem
Summary: reduce complexity by factoring synchronizer.cpp
Reviewed-by: dholmes, never, coleenp
author | acorn |
---|---|
date | Fri, 22 Oct 2010 15:59:34 -0400 |
parents | 0715f0cf171d |
children | 2d26b0046e0d f95d63e2154a |
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--- a/src/share/vm/runtime/thread.hpp Mon Oct 18 09:33:24 2010 -0700 +++ b/src/share/vm/runtime/thread.hpp Fri Oct 22 15:59:34 2010 -0400 @@ -30,6 +30,7 @@ class ThreadStatistics; class ConcurrentLocksDump; class ParkEvent ; +class Parker; class ciEnv; class CompileThread; @@ -544,7 +545,6 @@ static void muxAcquire (volatile intptr_t * Lock, const char * Name) ; static void muxAcquireW (volatile intptr_t * Lock, ParkEvent * ev) ; static void muxRelease (volatile intptr_t * Lock) ; - }; // Inline implementation of Thread::current() @@ -1769,100 +1769,3 @@ } }; -// ParkEvents are type-stable and immortal. -// -// Lifecycle: Once a ParkEvent is associated with a thread that ParkEvent remains -// associated with the thread for the thread's entire lifetime - the relationship is -// stable. A thread will be associated at most one ParkEvent. When the thread -// expires, the ParkEvent moves to the EventFreeList. New threads attempt to allocate from -// the EventFreeList before creating a new Event. Type-stability frees us from -// worrying about stale Event or Thread references in the objectMonitor subsystem. -// (A reference to ParkEvent is always valid, even though the event may no longer be associated -// with the desired or expected thread. A key aspect of this design is that the callers of -// park, unpark, etc must tolerate stale references and spurious wakeups). -// -// Only the "associated" thread can block (park) on the ParkEvent, although -// any other thread can unpark a reachable parkevent. Park() is allowed to -// return spuriously. In fact park-unpark a really just an optimization to -// avoid unbounded spinning and surrender the CPU to be a polite system citizen. -// A degenerate albeit "impolite" park-unpark implementation could simply return. -// See http://blogs.sun.com/dave for more details. -// -// Eventually I'd like to eliminate Events and ObjectWaiters, both of which serve as -// thread proxies, and simply make the THREAD structure type-stable and persistent. -// Currently, we unpark events associated with threads, but ideally we'd just -// unpark threads. -// -// The base-class, PlatformEvent, is platform-specific while the ParkEvent is -// platform-independent. PlatformEvent provides park(), unpark(), etc., and -// is abstract -- that is, a PlatformEvent should never be instantiated except -// as part of a ParkEvent. -// Equivalently we could have defined a platform-independent base-class that -// exported Allocate(), Release(), etc. The platform-specific class would extend -// that base-class, adding park(), unpark(), etc. -// -// A word of caution: The JVM uses 2 very similar constructs: -// 1. ParkEvent are used for Java-level "monitor" synchronization. -// 2. Parkers are used by JSR166-JUC park-unpark. -// -// We'll want to eventually merge these redundant facilities and use ParkEvent. - - -class ParkEvent : public os::PlatformEvent { - private: - ParkEvent * FreeNext ; - - // Current association - Thread * AssociatedWith ; - intptr_t RawThreadIdentity ; // LWPID etc - volatile int Incarnation ; - - // diagnostic : keep track of last thread to wake this thread. - // this is useful for construction of dependency graphs. - void * LastWaker ; - - public: - // MCS-CLH list linkage and Native Mutex/Monitor - ParkEvent * volatile ListNext ; - ParkEvent * volatile ListPrev ; - volatile intptr_t OnList ; - volatile int TState ; - volatile int Notified ; // for native monitor construct - volatile int IsWaiting ; // Enqueued on WaitSet - - - private: - static ParkEvent * volatile FreeList ; - static volatile int ListLock ; - - // It's prudent to mark the dtor as "private" - // ensuring that it's not visible outside the package. - // Unfortunately gcc warns about such usage, so - // we revert to the less desirable "protected" visibility. - // The other compilers accept private dtors. - - protected: // Ensure dtor is never invoked - ~ParkEvent() { guarantee (0, "invariant") ; } - - ParkEvent() : PlatformEvent() { - AssociatedWith = NULL ; - FreeNext = NULL ; - ListNext = NULL ; - ListPrev = NULL ; - OnList = 0 ; - TState = 0 ; - Notified = 0 ; - IsWaiting = 0 ; - } - - // We use placement-new to force ParkEvent instances to be - // aligned on 256-byte address boundaries. This ensures that the least - // significant byte of a ParkEvent address is always 0. - - void * operator new (size_t sz) ; - void operator delete (void * a) ; - - public: - static ParkEvent * Allocate (Thread * t) ; - static void Release (ParkEvent * e) ; -} ;