src/share/vm/gc/shared/gcLocker.hpp

*** 31,46 ****
  #include "oops/oop.hpp"
  
  // The direct lock/unlock calls do not force a collection if an unlock
  // decrements the count to zero. Avoid calling these if at all possible.
  
! class GC_locker: public AllStatic {
   private:
    // The _jni_lock_count keeps track of the number of threads that are
    // currently in a critical region.  It's only kept up to date when
    // _needs_gc is true.  The current value is computed during
!   // safepointing and decremented during the slow path of GC_locker
    // unlocking.
    static volatile jint _jni_lock_count;  // number of jni active instances.
    static volatile bool _needs_gc;        // heap is filling, we need a GC
                                           // note: bool is typedef'd as jint
    static volatile bool _doing_gc;        // unlock_critical() is doing a GC
--- 31,46 ----
  #include "oops/oop.hpp"
  
  // The direct lock/unlock calls do not force a collection if an unlock
  // decrements the count to zero. Avoid calling these if at all possible.
  
! class GCLocker: public AllStatic {
   private:
    // The _jni_lock_count keeps track of the number of threads that are
    // currently in a critical region.  It's only kept up to date when
    // _needs_gc is true.  The current value is computed during
!   // safepointing and decremented during the slow path of GCLocker
    // unlocking.
    static volatile jint _jni_lock_count;  // number of jni active instances.
    static volatile bool _needs_gc;        // heap is filling, we need a GC
                                           // note: bool is typedef'd as jint
    static volatile bool _doing_gc;        // unlock_critical() is doing a GC
*** 101,111 ****
    // return from this method that "!needs_gc()" since that is
    // not a stable predicate.
    static void stall_until_clear();
  
    // The following two methods are used for JNI critical regions.
!   // If we find that we failed to perform a GC because the GC_locker
    // was active, arrange for one as soon as possible by allowing
    // all threads in critical regions to complete, but not allowing
    // other critical regions to be entered. The reasons for that are:
    // 1) a GC request won't be starved by overlapping JNI critical
    //    region activities, which can cause unnecessary OutOfMemory errors.
--- 101,111 ----
    // return from this method that "!needs_gc()" since that is
    // not a stable predicate.
    static void stall_until_clear();
  
    // The following two methods are used for JNI critical regions.
!   // If we find that we failed to perform a GC because the GCLocker
    // was active, arrange for one as soon as possible by allowing
    // all threads in critical regions to complete, but not allowing
    // other critical regions to be entered. The reasons for that are:
    // 1) a GC request won't be starved by overlapping JNI critical
    //    region activities, which can cause unnecessary OutOfMemory errors.
*** 124,134 ****
    // Each of the following two method is split into a fast path and a
    // slow path. JNICritical_lock is only grabbed in the slow path.
    // _needs_gc is initially false and every java thread will go
    // through the fast path, which simply increments or decrements the
    // current thread's critical count.  When GC happens at a safepoint,
!   // GC_locker::is_active() is checked. Since there is no safepoint in
    // the fast path of lock_critical() and unlock_critical(), there is
    // no race condition between the fast path and GC. After _needs_gc
    // is set at a safepoint, every thread will go through the slow path
    // after the safepoint.  Since after a safepoint, each of the
    // following two methods is either entered from the method entry and
--- 124,134 ----
    // Each of the following two method is split into a fast path and a
    // slow path. JNICritical_lock is only grabbed in the slow path.
    // _needs_gc is initially false and every java thread will go
    // through the fast path, which simply increments or decrements the
    // current thread's critical count.  When GC happens at a safepoint,
!   // GCLocker::is_active() is checked. Since there is no safepoint in
    // the fast path of lock_critical() and unlock_critical(), there is
    // no race condition between the fast path and GC. After _needs_gc
    // is set at a safepoint, every thread will go through the slow path
    // after the safepoint.  Since after a safepoint, each of the
    // following two methods is either entered from the method entry and
*** 140,262 ****
  
    static address needs_gc_address() { return (address) &_needs_gc; }
  };
  
  
! // A No_GC_Verifier object can be placed in methods where one assumes that
  // no garbage collection will occur. The destructor will verify this property
  // unless the constructor is called with argument false (not verifygc).
  //
  // The check will only be done in debug mode and if verifygc true.
  
! class No_GC_Verifier: public StackObj {
!  friend class Pause_No_GC_Verifier;
  
   protected:
    bool _verifygc;
    unsigned int _old_invocations;
  
   public:
  #ifdef ASSERT
!   No_GC_Verifier(bool verifygc = true);
!   ~No_GC_Verifier();
  #else
!   No_GC_Verifier(bool verifygc = true) {}
!   ~No_GC_Verifier() {}
  #endif
  };
  
! // A Pause_No_GC_Verifier is used to temporarily pause the behavior
! // of a No_GC_Verifier object. If we are not in debug mode or if the
! // No_GC_Verifier object has a _verifygc value of false, then there
  // is nothing to do.
  
! class Pause_No_GC_Verifier: public StackObj {
   private:
!   No_GC_Verifier * _ngcv;
  
   public:
  #ifdef ASSERT
!   Pause_No_GC_Verifier(No_GC_Verifier * ngcv);
!   ~Pause_No_GC_Verifier();
  #else
!   Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {}
!   ~Pause_No_GC_Verifier() {}
  #endif
  };
  
  
! // A No_Safepoint_Verifier object will throw an assertion failure if
  // the current thread passes a possible safepoint while this object is
  // instantiated. A safepoint, will either be: an oop allocation, blocking
  // on a Mutex or JavaLock, or executing a VM operation.
  //
! // If StrictSafepointChecks is turned off, it degrades into a No_GC_Verifier
  //
! class No_Safepoint_Verifier : public No_GC_Verifier {
!  friend class Pause_No_Safepoint_Verifier;
  
   private:
    bool _activated;
    Thread *_thread;
   public:
  #ifdef ASSERT
!   No_Safepoint_Verifier(bool activated = true, bool verifygc = true ) :
!     No_GC_Verifier(verifygc),
      _activated(activated) {
      _thread = Thread::current();
      if (_activated) {
        _thread->_allow_allocation_count++;
        _thread->_allow_safepoint_count++;
      }
    }
  
!   ~No_Safepoint_Verifier() {
      if (_activated) {
        _thread->_allow_allocation_count--;
        _thread->_allow_safepoint_count--;
      }
    }
  #else
!   No_Safepoint_Verifier(bool activated = true, bool verifygc = true) : No_GC_Verifier(verifygc){}
!   ~No_Safepoint_Verifier() {}
  #endif
  };
  
! // A Pause_No_Safepoint_Verifier is used to temporarily pause the
! // behavior of a No_Safepoint_Verifier object. If we are not in debug
! // mode then there is nothing to do. If the No_Safepoint_Verifier
  // object has an _activated value of false, then there is nothing to
  // do for safepoint and allocation checking, but there may still be
! // something to do for the underlying No_GC_Verifier object.
  
! class Pause_No_Safepoint_Verifier : public Pause_No_GC_Verifier {
   private:
!   No_Safepoint_Verifier * _nsv;
  
   public:
  #ifdef ASSERT
!   Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv)
!     : Pause_No_GC_Verifier(nsv) {
  
      _nsv = nsv;
      if (_nsv->_activated) {
        _nsv->_thread->_allow_allocation_count--;
        _nsv->_thread->_allow_safepoint_count--;
      }
    }
  
!   ~Pause_No_Safepoint_Verifier() {
      if (_nsv->_activated) {
        _nsv->_thread->_allow_allocation_count++;
        _nsv->_thread->_allow_safepoint_count++;
      }
    }
  #else
!   Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv)
!     : Pause_No_GC_Verifier(nsv) {}
!   ~Pause_No_Safepoint_Verifier() {}
  #endif
  };
  
  // A SkipGCALot object is used to elide the usual effect of gc-a-lot
  // over a section of execution by a thread. Currently, it's used only to
--- 140,262 ----
  
    static address needs_gc_address() { return (address) &_needs_gc; }
  };
  
  
! // A NoGCVerifier object can be placed in methods where one assumes that
  // no garbage collection will occur. The destructor will verify this property
  // unless the constructor is called with argument false (not verifygc).
  //
  // The check will only be done in debug mode and if verifygc true.
  
! class NoGCVerifier: public StackObj {
!  friend class PauseNoGCVerifier;
  
   protected:
    bool _verifygc;
    unsigned int _old_invocations;
  
   public:
  #ifdef ASSERT
!   NoGCVerifier(bool verifygc = true);
!   ~NoGCVerifier();
  #else
!   NoGCVerifier(bool verifygc = true) {}
!   ~NoGCVerifier() {}
  #endif
  };
  
! // A PauseNoGCVerifier is used to temporarily pause the behavior
! // of a NoGCVerifier object. If we are not in debug mode or if the
! // NoGCVerifier object has a _verifygc value of false, then there
  // is nothing to do.
  
! class PauseNoGCVerifier: public StackObj {
   private:
!   NoGCVerifier * _ngcv;
  
   public:
  #ifdef ASSERT
!   PauseNoGCVerifier(NoGCVerifier * ngcv);
!   ~PauseNoGCVerifier();
  #else
!   PauseNoGCVerifier(NoGCVerifier * ngcv) {}
!   ~PauseNoGCVerifier() {}
  #endif
  };
  
  
! // A NoSafepointVerifier object will throw an assertion failure if
  // the current thread passes a possible safepoint while this object is
  // instantiated. A safepoint, will either be: an oop allocation, blocking
  // on a Mutex or JavaLock, or executing a VM operation.
  //
! // If StrictSafepointChecks is turned off, it degrades into a NoGCVerifier
  //
! class NoSafepointVerifier : public NoGCVerifier {
!  friend class PauseNoSafepointVerifier;
  
   private:
    bool _activated;
    Thread *_thread;
   public:
  #ifdef ASSERT
!   NoSafepointVerifier(bool activated = true, bool verifygc = true ) :
!     NoGCVerifier(verifygc),
      _activated(activated) {
      _thread = Thread::current();
      if (_activated) {
        _thread->_allow_allocation_count++;
        _thread->_allow_safepoint_count++;
      }
    }
  
!   ~NoSafepointVerifier() {
      if (_activated) {
        _thread->_allow_allocation_count--;
        _thread->_allow_safepoint_count--;
      }
    }
  #else
!   NoSafepointVerifier(bool activated = true, bool verifygc = true) : NoGCVerifier(verifygc){}
!   ~NoSafepointVerifier() {}
  #endif
  };
  
! // A PauseNoSafepointVerifier is used to temporarily pause the
! // behavior of a NoSafepointVerifier object. If we are not in debug
! // mode then there is nothing to do. If the NoSafepointVerifier
  // object has an _activated value of false, then there is nothing to
  // do for safepoint and allocation checking, but there may still be
! // something to do for the underlying NoGCVerifier object.
  
! class PauseNoSafepointVerifier : public PauseNoGCVerifier {
   private:
!   NoSafepointVerifier * _nsv;
  
   public:
  #ifdef ASSERT
!   PauseNoSafepointVerifier(NoSafepointVerifier * nsv)
!     : PauseNoGCVerifier(nsv) {
  
      _nsv = nsv;
      if (_nsv->_activated) {
        _nsv->_thread->_allow_allocation_count--;
        _nsv->_thread->_allow_safepoint_count--;
      }
    }
  
!   ~PauseNoSafepointVerifier() {
      if (_nsv->_activated) {
        _nsv->_thread->_allow_allocation_count++;
        _nsv->_thread->_allow_safepoint_count++;
      }
    }
  #else
!   PauseNoSafepointVerifier(NoSafepointVerifier * nsv)
!     : PauseNoGCVerifier(nsv) {}
!   ~PauseNoSafepointVerifier() {}
  #endif
  };
  
  // A SkipGCALot object is used to elide the usual effect of gc-a-lot
  // over a section of execution by a thread. Currently, it's used only to
*** 285,330 ****
  
  // JRT_LEAF currently can be called from either _thread_in_Java or
  // _thread_in_native mode. In _thread_in_native, it is ok
  // for another thread to trigger GC. The rest of the JRT_LEAF
  // rules apply.
! class JRT_Leaf_Verifier : public No_Safepoint_Verifier {
    static bool should_verify_GC();
   public:
  #ifdef ASSERT
!   JRT_Leaf_Verifier();
!   ~JRT_Leaf_Verifier();
  #else
!   JRT_Leaf_Verifier() {}
!   ~JRT_Leaf_Verifier() {}
  #endif
  };
  
! // A No_Alloc_Verifier object can be placed in methods where one assumes that
  // no allocation will occur. The destructor will verify this property
  // unless the constructor is called with argument false (not activated).
  //
  // The check will only be done in debug mode and if activated.
  // Note: this only makes sense at safepoints (otherwise, other threads may
  // allocate concurrently.)
  
! class No_Alloc_Verifier : public StackObj {
   private:
    bool  _activated;
  
   public:
  #ifdef ASSERT
!   No_Alloc_Verifier(bool activated = true) {
      _activated = activated;
      if (_activated) Thread::current()->_allow_allocation_count++;
    }
  
!   ~No_Alloc_Verifier() {
      if (_activated) Thread::current()->_allow_allocation_count--;
    }
  #else
!   No_Alloc_Verifier(bool activated = true) {}
!   ~No_Alloc_Verifier() {}
  #endif
  };
  
  #endif // SHARE_VM_GC_SHARED_GCLOCKER_HPP
--- 285,330 ----
  
  // JRT_LEAF currently can be called from either _thread_in_Java or
  // _thread_in_native mode. In _thread_in_native, it is ok
  // for another thread to trigger GC. The rest of the JRT_LEAF
  // rules apply.
! class JRTLeafVerifier : public NoSafepointVerifier {
    static bool should_verify_GC();
   public:
  #ifdef ASSERT
!   JRTLeafVerifier();
!   ~JRTLeafVerifier();
  #else
!   JRTLeafVerifier() {}
!   ~JRTLeafVerifier() {}
  #endif
  };
  
! // A NoAllocVerifier object can be placed in methods where one assumes that
  // no allocation will occur. The destructor will verify this property
  // unless the constructor is called with argument false (not activated).
  //
  // The check will only be done in debug mode and if activated.
  // Note: this only makes sense at safepoints (otherwise, other threads may
  // allocate concurrently.)
  
! class NoAllocVerifier : public StackObj {
   private:
    bool  _activated;
  
   public:
  #ifdef ASSERT
!   NoAllocVerifier(bool activated = true) {
      _activated = activated;
      if (_activated) Thread::current()->_allow_allocation_count++;
    }
  
!   ~NoAllocVerifier() {
      if (_activated) Thread::current()->_allow_allocation_count--;
    }
  #else
!   NoAllocVerifier(bool activated = true) {}
!   ~NoAllocVerifier() {}
  #endif
  };
  
  #endif // SHARE_VM_GC_SHARED_GCLOCKER_HPP