jdk8-mips64-public/hotspot: src/share/vm/utilities/taskqueue.hpp@aefa2e84b424 (annotated)

src/share/vm/utilities/taskqueue.hpp@aefa2e84b424 (annotated)

src/share/vm/utilities/taskqueue.hpp

Thu, 19 Mar 2015 19:53:34 +0100

author: zmajo
date: Thu, 19 Mar 2015 19:53:34 +0100
changeset 7638: aefa2e84b424
parent 6911: ce8f6bb717c9
child 7535: 7ae4e26cb1e0
child 8611: a753c8401458
permissions: -rw-r--r--

8074869: C2 code generator can replace -0.0f with +0.0f on Linux
Summary: Instead of 'fpclass', use cast float->int and double->long to check if value is +0.0f and +0.0d, respectively.
Reviewed-by: kvn, simonis, dlong

 /*
  * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #ifndef SHARE_VM_UTILITIES_TASKQUEUE_HPP
 #define SHARE_VM_UTILITIES_TASKQUEUE_HPP
 #include "memory/allocation.hpp"
 #include "memory/allocation.inline.hpp"
 #include "runtime/mutex.hpp"
 #include "runtime/orderAccess.inline.hpp"
 #include "utilities/stack.hpp"
 // Simple TaskQueue stats that are collected by default in debug builds.
 #if !defined(TASKQUEUE_STATS) && defined(ASSERT)
 #define TASKQUEUE_STATS 1
 #elif !defined(TASKQUEUE_STATS)
 #define TASKQUEUE_STATS 0
 #endif
 #if TASKQUEUE_STATS
 #define TASKQUEUE_STATS_ONLY(code) code
 #else
 #define TASKQUEUE_STATS_ONLY(code)
 #endif // TASKQUEUE_STATS
 #if TASKQUEUE_STATS
 class TaskQueueStats {
 public:
   enum StatId {
     push,             // number of taskqueue pushes
     pop,              // number of taskqueue pops
     pop_slow,         // subset of taskqueue pops that were done slow-path
     steal_attempt,    // number of taskqueue steal attempts
     steal,            // number of taskqueue steals
     overflow,         // number of overflow pushes
     overflow_max_len, // max length of overflow stack
     last_stat_id
   };
 public:
   inline TaskQueueStats()       { reset(); }
   inline void record_push()     { ++_stats[push]; }
   inline void record_pop()      { ++_stats[pop]; }
   inline void record_pop_slow() { record_pop(); ++_stats[pop_slow]; }
   inline void record_steal(bool success);
   inline void record_overflow(size_t new_length);
   TaskQueueStats & operator +=(const TaskQueueStats & addend);
   inline size_t get(StatId id) const { return _stats[id]; }
   inline const size_t* get() const   { return _stats; }
   inline void reset();
   // Print the specified line of the header (does not include a line separator).
   static void print_header(unsigned int line, outputStream* const stream = tty,
                            unsigned int width = 10);
   // Print the statistics (does not include a line separator).
   void print(outputStream* const stream = tty, unsigned int width = 10) const;
   DEBUG_ONLY(void verify() const;)
 private:
   size_t                    _stats[last_stat_id];
   static const char * const _names[last_stat_id];
 };
 void TaskQueueStats::record_steal(bool success) {
   ++_stats[steal_attempt];
   if (success) ++_stats[steal];
 }
 void TaskQueueStats::record_overflow(size_t new_len) {
   ++_stats[overflow];
   if (new_len > _stats[overflow_max_len]) _stats[overflow_max_len] = new_len;
 }
 void TaskQueueStats::reset() {
   memset(_stats, 0, sizeof(_stats));
 }
 #endif // TASKQUEUE_STATS
 // TaskQueueSuper collects functionality common to all GenericTaskQueue instances.
 template <unsigned int N, MEMFLAGS F>
 class TaskQueueSuper: public CHeapObj<F> {
 protected:
   // Internal type for indexing the queue; also used for the tag.
   typedef NOT_LP64(uint16_t) LP64_ONLY(uint32_t) idx_t;
   // The first free element after the last one pushed (mod N).
   volatile uint _bottom;
   enum { MOD_N_MASK = N - 1 };
   class Age {
   public:
     Age(size_t data = 0)         { _data = data; }
     Age(const Age& age)          { _data = age._data; }
     Age(idx_t top, idx_t tag)    { _fields._top = top; _fields._tag = tag; }
     Age   get()        const volatile { return _data; }
     void  set(Age age) volatile       { _data = age._data; }
     idx_t top()        const volatile { return _fields._top; }
     idx_t tag()        const volatile { return _fields._tag; }
     // Increment top; if it wraps, increment tag also.
     void increment() {
       _fields._top = increment_index(_fields._top);
       if (_fields._top == 0) ++_fields._tag;
     }
     Age cmpxchg(const Age new_age, const Age old_age) volatile {
       return (size_t) Atomic::cmpxchg_ptr((intptr_t)new_age._data,
                                           (volatile intptr_t *)&_data,
                                           (intptr_t)old_age._data);
     }
     bool operator ==(const Age& other) const { return _data == other._data; }
   private:
     struct fields {
       idx_t _top;
       idx_t _tag;
     };
     union {
       size_t _data;
       fields _fields;
     };
   };
   volatile Age _age;
   // These both operate mod N.
   static uint increment_index(uint ind) {
     return (ind + 1) & MOD_N_MASK;
   }
   static uint decrement_index(uint ind) {
     return (ind - 1) & MOD_N_MASK;
   }
   // Returns a number in the range [0..N).  If the result is "N-1", it should be
   // interpreted as 0.
   uint dirty_size(uint bot, uint top) const {
     return (bot - top) & MOD_N_MASK;
   }
   // Returns the size corresponding to the given "bot" and "top".
   uint size(uint bot, uint top) const {
     uint sz = dirty_size(bot, top);
     // Has the queue "wrapped", so that bottom is less than top?  There's a
     // complicated special case here.  A pair of threads could perform pop_local
     // and pop_global operations concurrently, starting from a state in which
     // _bottom == _top+1.  The pop_local could succeed in decrementing _bottom,
     // and the pop_global in incrementing _top (in which case the pop_global
     // will be awarded the contested queue element.)  The resulting state must
     // be interpreted as an empty queue.  (We only need to worry about one such
     // event: only the queue owner performs pop_local's, and several concurrent
     // threads attempting to perform the pop_global will all perform the same
     // CAS, and only one can succeed.)  Any stealing thread that reads after
     // either the increment or decrement will see an empty queue, and will not
     // join the competitors.  The "sz == -1 || sz == N-1" state will not be
     // modified by concurrent queues, so the owner thread can reset the state to
     // _bottom == top so subsequent pushes will be performed normally.
     return (sz == N - 1) ? 0 : sz;
   }
 public:
   TaskQueueSuper() : _bottom(0), _age() {}
   // Return true if the TaskQueue contains/does not contain any tasks.
   bool peek()     const { return _bottom != _age.top(); }
   bool is_empty() const { return size() == 0; }
   // Return an estimate of the number of elements in the queue.
   // The "careful" version admits the possibility of pop_local/pop_global
   // races.
   uint size() const {
     return size(_bottom, _age.top());
   }
   uint dirty_size() const {
     return dirty_size(_bottom, _age.top());
   }
   void set_empty() {
     _bottom = 0;
     _age.set(0);
   }
   // Maximum number of elements allowed in the queue.  This is two less
   // than the actual queue size, for somewhat complicated reasons.
   uint max_elems() const { return N - 2; }
   // Total size of queue.
   static const uint total_size() { return N; }
   TASKQUEUE_STATS_ONLY(TaskQueueStats stats;)
 };
 //
 // GenericTaskQueue implements an ABP, Aurora-Blumofe-Plaxton, double-
 // ended-queue (deque), intended for use in work stealing. Queue operations
 // are non-blocking.
 //
 // A queue owner thread performs push() and pop_local() operations on one end
 // of the queue, while other threads may steal work using the pop_global()
 // method.
 //
 // The main difference to the original algorithm is that this
 // implementation allows wrap-around at the end of its allocated
 // storage, which is an array.
 //
 // The original paper is:
 //
 // Arora, N. S., Blumofe, R. D., and Plaxton, C. G.
 // Thread scheduling for multiprogrammed multiprocessors.
 // Theory of Computing Systems 34, 2 (2001), 115-144.
 //
 // The following paper provides an correctness proof and an
 // implementation for weakly ordered memory models including (pseudo-)
 // code containing memory barriers for a Chase-Lev deque. Chase-Lev is
 // similar to ABP, with the main difference that it allows resizing of the
 // underlying storage:
 //
 // Le, N. M., Pop, A., Cohen A., and Nardell, F. Z.
 // Correct and efficient work-stealing for weak memory models
 // Proceedings of the 18th ACM SIGPLAN symposium on Principles and
 // practice of parallel programming (PPoPP 2013), 69-80
 //
 template <class E, MEMFLAGS F, unsigned int N = TASKQUEUE_SIZE>
 class GenericTaskQueue: public TaskQueueSuper<N, F> {
   ArrayAllocator<E, F> _array_allocator;
 protected:
   typedef typename TaskQueueSuper<N, F>::Age Age;
   typedef typename TaskQueueSuper<N, F>::idx_t idx_t;
   using TaskQueueSuper<N, F>::_bottom;
   using TaskQueueSuper<N, F>::_age;
   using TaskQueueSuper<N, F>::increment_index;
   using TaskQueueSuper<N, F>::decrement_index;
   using TaskQueueSuper<N, F>::dirty_size;
 public:
   using TaskQueueSuper<N, F>::max_elems;
   using TaskQueueSuper<N, F>::size;
 #if  TASKQUEUE_STATS
   using TaskQueueSuper<N, F>::stats;
 #endif
 private:
   // Slow paths for push, pop_local.  (pop_global has no fast path.)
   bool push_slow(E t, uint dirty_n_elems);
   bool pop_local_slow(uint localBot, Age oldAge);
 public:
   typedef E element_type;
   // Initializes the queue to empty.
   GenericTaskQueue();
   void initialize();
   // Push the task "t" on the queue.  Returns "false" iff the queue is full.
   inline bool push(E t);
   // Attempts to claim a task from the "local" end of the queue (the most
   // recently pushed).  If successful, returns true and sets t to the task;
   // otherwise, returns false (the queue is empty).
   inline bool pop_local(volatile E& t);
   // Like pop_local(), but uses the "global" end of the queue (the least
   // recently pushed).
   bool pop_global(volatile E& t);
   // Delete any resource associated with the queue.
   ~GenericTaskQueue();
   // apply the closure to all elements in the task queue
   void oops_do(OopClosure* f);
 private:
   // Element array.
   volatile E* _elems;
 };
 template<class E, MEMFLAGS F, unsigned int N>
 GenericTaskQueue<E, F, N>::GenericTaskQueue() {
   assert(sizeof(Age) == sizeof(size_t), "Depends on this.");
 }
 template<class E, MEMFLAGS F, unsigned int N>
 void GenericTaskQueue<E, F, N>::initialize() {
   _elems = _array_allocator.allocate(N);
 }
 template<class E, MEMFLAGS F, unsigned int N>
 void GenericTaskQueue<E, F, N>::oops_do(OopClosure* f) {
   // tty->print_cr("START OopTaskQueue::oops_do");
   uint iters = size();
   uint index = _bottom;
   for (uint i = 0; i < iters; ++i) {
     index = decrement_index(index);
     // tty->print_cr("  doing entry %d," INTPTR_T " -> " INTPTR_T,
     //            index, &_elems[index], _elems[index]);
     E* t = (E*)&_elems[index];      // cast away volatility
     oop* p = (oop*)t;
     assert((*t)->is_oop_or_null(), "Not an oop or null");
     f->do_oop(p);
   }
   // tty->print_cr("END OopTaskQueue::oops_do");
 }
 template<class E, MEMFLAGS F, unsigned int N>
 bool GenericTaskQueue<E, F, N>::push_slow(E t, uint dirty_n_elems) {
   if (dirty_n_elems == N - 1) {
     // Actually means 0, so do the push.
     uint localBot = _bottom;
     // g++ complains if the volatile result of the assignment is
     // unused, so we cast the volatile away.  We cannot cast directly
     // to void, because gcc treats that as not using the result of the
     // assignment.  However, casting to E& means that we trigger an
     // unused-value warning.  So, we cast the E& to void.
     (void)const_cast<E&>(_elems[localBot] = t);
     OrderAccess::release_store(&_bottom, increment_index(localBot));
     TASKQUEUE_STATS_ONLY(stats.record_push());
     return true;
   }
   return false;
 }
 // pop_local_slow() is done by the owning thread and is trying to
 // get the last task in the queue.  It will compete with pop_global()
 // that will be used by other threads.  The tag age is incremented
 // whenever the queue goes empty which it will do here if this thread
 // gets the last task or in pop_global() if the queue wraps (top == 0
 // and pop_global() succeeds, see pop_global()).
 template<class E, MEMFLAGS F, unsigned int N>
 bool GenericTaskQueue<E, F, N>::pop_local_slow(uint localBot, Age oldAge) {
   // This queue was observed to contain exactly one element; either this
   // thread will claim it, or a competing "pop_global".  In either case,
   // the queue will be logically empty afterwards.  Create a new Age value
   // that represents the empty queue for the given value of "_bottom".  (We
   // must also increment "tag" because of the case where "bottom == 1",
   // "top == 0".  A pop_global could read the queue element in that case,
   // then have the owner thread do a pop followed by another push.  Without
   // the incrementing of "tag", the pop_global's CAS could succeed,
   // allowing it to believe it has claimed the stale element.)
   Age newAge((idx_t)localBot, oldAge.tag() + 1);
   // Perhaps a competing pop_global has already incremented "top", in which
   // case it wins the element.
   if (localBot == oldAge.top()) {
     // No competing pop_global has yet incremented "top"; we'll try to
     // install new_age, thus claiming the element.
     Age tempAge = _age.cmpxchg(newAge, oldAge);
     if (tempAge == oldAge) {
       // We win.
       assert(dirty_size(localBot, _age.top()) != N - 1, "sanity");
       TASKQUEUE_STATS_ONLY(stats.record_pop_slow());
       return true;
     }
   }
   // We lose; a completing pop_global gets the element.  But the queue is empty
   // and top is greater than bottom.  Fix this representation of the empty queue
   // to become the canonical one.
   _age.set(newAge);
   assert(dirty_size(localBot, _age.top()) != N - 1, "sanity");
   return false;
 }
 template<class E, MEMFLAGS F, unsigned int N>
 bool GenericTaskQueue<E, F, N>::pop_global(volatile E& t) {
   Age oldAge = _age.get();
   // Architectures with weak memory model require a barrier here
   // to guarantee that bottom is not older than age,
   // which is crucial for the correctness of the algorithm.
 #if !(defined SPARC || defined IA32 || defined AMD64)
   OrderAccess::fence();
 #endif
   uint localBot = OrderAccess::load_acquire((volatile juint*)&_bottom);
   uint n_elems = size(localBot, oldAge.top());
   if (n_elems == 0) {
     return false;
   }
   // g++ complains if the volatile result of the assignment is
   // unused, so we cast the volatile away.  We cannot cast directly
   // to void, because gcc treats that as not using the result of the
   // assignment.  However, casting to E& means that we trigger an
   // unused-value warning.  So, we cast the E& to void.
   (void) const_cast<E&>(t = _elems[oldAge.top()]);
   Age newAge(oldAge);
   newAge.increment();
   Age resAge = _age.cmpxchg(newAge, oldAge);
   // Note that using "_bottom" here might fail, since a pop_local might
   // have decremented it.
   assert(dirty_size(localBot, newAge.top()) != N - 1, "sanity");
   return resAge == oldAge;
 }
 template<class E, MEMFLAGS F, unsigned int N>
 GenericTaskQueue<E, F, N>::~GenericTaskQueue() {
   FREE_C_HEAP_ARRAY(E, _elems, F);
 }
 // OverflowTaskQueue is a TaskQueue that also includes an overflow stack for
 // elements that do not fit in the TaskQueue.
 //
 // This class hides two methods from super classes:
 //
 // push() - push onto the task queue or, if that fails, onto the overflow stack
 // is_empty() - return true if both the TaskQueue and overflow stack are empty
 //
 // Note that size() is not hidden--it returns the number of elements in the
 // TaskQueue, and does not include the size of the overflow stack.  This
 // simplifies replacement of GenericTaskQueues with OverflowTaskQueues.
 template<class E, MEMFLAGS F, unsigned int N = TASKQUEUE_SIZE>
 class OverflowTaskQueue: public GenericTaskQueue<E, F, N>
 {
 public:
   typedef Stack<E, F>               overflow_t;
   typedef GenericTaskQueue<E, F, N> taskqueue_t;
   TASKQUEUE_STATS_ONLY(using taskqueue_t::stats;)
   // Push task t onto the queue or onto the overflow stack.  Return true.
   inline bool push(E t);
   // Attempt to pop from the overflow stack; return true if anything was popped.
   inline bool pop_overflow(E& t);
   inline overflow_t* overflow_stack() { return &_overflow_stack; }
   inline bool taskqueue_empty() const { return taskqueue_t::is_empty(); }
   inline bool overflow_empty()  const { return _overflow_stack.is_empty(); }
   inline bool is_empty()        const {
     return taskqueue_empty() && overflow_empty();
   }
 private:
   overflow_t _overflow_stack;
 };
 template <class E, MEMFLAGS F, unsigned int N>
 bool OverflowTaskQueue<E, F, N>::push(E t)
 {
   if (!taskqueue_t::push(t)) {
     overflow_stack()->push(t);
     TASKQUEUE_STATS_ONLY(stats.record_overflow(overflow_stack()->size()));
   }
   return true;
 }
 template <class E, MEMFLAGS F, unsigned int N>
 bool OverflowTaskQueue<E, F, N>::pop_overflow(E& t)
 {
   if (overflow_empty()) return false;
   t = overflow_stack()->pop();
   return true;
 }
 class TaskQueueSetSuper {
 protected:
   static int randomParkAndMiller(int* seed0);
 public:
   // Returns "true" if some TaskQueue in the set contains a task.
   virtual bool peek() = 0;
 };
 template <MEMFLAGS F> class TaskQueueSetSuperImpl: public CHeapObj<F>, public TaskQueueSetSuper {
 };
 template<class T, MEMFLAGS F>
 class GenericTaskQueueSet: public TaskQueueSetSuperImpl<F> {
 private:
   uint _n;
   T** _queues;
 public:
   typedef typename T::element_type E;
   GenericTaskQueueSet(int n) : _n(n) {
     typedef T* GenericTaskQueuePtr;
     _queues = NEW_C_HEAP_ARRAY(GenericTaskQueuePtr, n, F);
     for (int i = 0; i < n; i++) {
       _queues[i] = NULL;
     }
   }
   bool steal_best_of_2(uint queue_num, int* seed, E& t);
   void register_queue(uint i, T* q);
   T* queue(uint n);
   // The thread with queue number "queue_num" (and whose random number seed is
   // at "seed") is trying to steal a task from some other queue.  (It may try
   // several queues, according to some configuration parameter.)  If some steal
   // succeeds, returns "true" and sets "t" to the stolen task, otherwise returns
   // false.
   bool steal(uint queue_num, int* seed, E& t);
   bool peek();
 };
 template<class T, MEMFLAGS F> void
 GenericTaskQueueSet<T, F>::register_queue(uint i, T* q) {
   assert(i < _n, "index out of range.");
   _queues[i] = q;
 }
 template<class T, MEMFLAGS F> T*
 GenericTaskQueueSet<T, F>::queue(uint i) {
   return _queues[i];
 }
 template<class T, MEMFLAGS F> bool
 GenericTaskQueueSet<T, F>::steal(uint queue_num, int* seed, E& t) {
   for (uint i = 0; i < 2 * _n; i++) {
     if (steal_best_of_2(queue_num, seed, t)) {
       TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(true));
       return true;
     }
   }
   TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(false));
   return false;
 }
 template<class T, MEMFLAGS F> bool
 GenericTaskQueueSet<T, F>::steal_best_of_2(uint queue_num, int* seed, E& t) {
   if (_n > 2) {
     uint k1 = queue_num;
     while (k1 == queue_num) k1 = TaskQueueSetSuper::randomParkAndMiller(seed) % _n;
     uint k2 = queue_num;
     while (k2 == queue_num || k2 == k1) k2 = TaskQueueSetSuper::randomParkAndMiller(seed) % _n;
     // Sample both and try the larger.
     uint sz1 = _queues[k1]->size();
     uint sz2 = _queues[k2]->size();
     if (sz2 > sz1) return _queues[k2]->pop_global(t);
     else return _queues[k1]->pop_global(t);
   } else if (_n == 2) {
     // Just try the other one.
     uint k = (queue_num + 1) % 2;
     return _queues[k]->pop_global(t);
   } else {
     assert(_n == 1, "can't be zero.");
     return false;
   }
 }
 template<class T, MEMFLAGS F>
 bool GenericTaskQueueSet<T, F>::peek() {
   // Try all the queues.
   for (uint j = 0; j < _n; j++) {
     if (_queues[j]->peek())
       return true;
   }
   return false;
 }
 // When to terminate from the termination protocol.
 class TerminatorTerminator: public CHeapObj<mtInternal> {
 public:
   virtual bool should_exit_termination() = 0;
 };
 // A class to aid in the termination of a set of parallel tasks using
 // TaskQueueSet's for work stealing.
 #undef TRACESPINNING
 class ParallelTaskTerminator: public StackObj {
 private:
   int _n_threads;
   TaskQueueSetSuper* _queue_set;
   int _offered_termination;
 #ifdef TRACESPINNING
   static uint _total_yields;
   static uint _total_spins;
   static uint _total_peeks;
 #endif
   bool peek_in_queue_set();
 protected:
   virtual void yield();
   void sleep(uint millis);
 public:
   // "n_threads" is the number of threads to be terminated.  "queue_set" is a
   // queue sets of work queues of other threads.
   ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set);
   // The current thread has no work, and is ready to terminate if everyone
   // else is.  If returns "true", all threads are terminated.  If returns
   // "false", available work has been observed in one of the task queues,
   // so the global task is not complete.
   bool offer_termination() {
     return offer_termination(NULL);
   }
   // As above, but it also terminates if the should_exit_termination()
   // method of the terminator parameter returns true. If terminator is
   // NULL, then it is ignored.
   bool offer_termination(TerminatorTerminator* terminator);
   // Reset the terminator, so that it may be reused again.
   // The caller is responsible for ensuring that this is done
   // in an MT-safe manner, once the previous round of use of
   // the terminator is finished.
   void reset_for_reuse();
   // Same as above but the number of parallel threads is set to the
   // given number.
   void reset_for_reuse(int n_threads);
 #ifdef TRACESPINNING
   static uint total_yields() { return _total_yields; }
   static uint total_spins() { return _total_spins; }
   static uint total_peeks() { return _total_peeks; }
   static void print_termination_counts();
 #endif
 };
 template<class E, MEMFLAGS F, unsigned int N> inline bool
 GenericTaskQueue<E, F, N>::push(E t) {
   uint localBot = _bottom;
   assert(localBot < N, "_bottom out of range.");
   idx_t top = _age.top();
   uint dirty_n_elems = dirty_size(localBot, top);
   assert(dirty_n_elems < N, "n_elems out of range.");
   if (dirty_n_elems < max_elems()) {
     // g++ complains if the volatile result of the assignment is
     // unused, so we cast the volatile away.  We cannot cast directly
     // to void, because gcc treats that as not using the result of the
     // assignment.  However, casting to E& means that we trigger an
     // unused-value warning.  So, we cast the E& to void.
     (void) const_cast<E&>(_elems[localBot] = t);
     OrderAccess::release_store(&_bottom, increment_index(localBot));
     TASKQUEUE_STATS_ONLY(stats.record_push());
     return true;
   } else {
     return push_slow(t, dirty_n_elems);
   }
 }
 template<class E, MEMFLAGS F, unsigned int N> inline bool
 GenericTaskQueue<E, F, N>::pop_local(volatile E& t) {
   uint localBot = _bottom;
   // This value cannot be N-1.  That can only occur as a result of
   // the assignment to bottom in this method.  If it does, this method
   // resets the size to 0 before the next call (which is sequential,
   // since this is pop_local.)
   uint dirty_n_elems = dirty_size(localBot, _age.top());
   assert(dirty_n_elems != N - 1, "Shouldn't be possible...");
   if (dirty_n_elems == 0) return false;
   localBot = decrement_index(localBot);
   _bottom = localBot;
   // This is necessary to prevent any read below from being reordered
   // before the store just above.
   OrderAccess::fence();
   // g++ complains if the volatile result of the assignment is
   // unused, so we cast the volatile away.  We cannot cast directly
   // to void, because gcc treats that as not using the result of the
   // assignment.  However, casting to E& means that we trigger an
   // unused-value warning.  So, we cast the E& to void.
   (void) const_cast<E&>(t = _elems[localBot]);
   // This is a second read of "age"; the "size()" above is the first.
   // If there's still at least one element in the queue, based on the
   // "_bottom" and "age" we've read, then there can be no interference with
   // a "pop_global" operation, and we're done.
   idx_t tp = _age.top();    // XXX
   if (size(localBot, tp) > 0) {
     assert(dirty_size(localBot, tp) != N - 1, "sanity");
     TASKQUEUE_STATS_ONLY(stats.record_pop());
     return true;
   } else {
     // Otherwise, the queue contained exactly one element; we take the slow
     // path.
     return pop_local_slow(localBot, _age.get());
   }
 }
 typedef GenericTaskQueue<oop, mtGC>             OopTaskQueue;
 typedef GenericTaskQueueSet<OopTaskQueue, mtGC> OopTaskQueueSet;
 #ifdef _MSC_VER
 #pragma warning(push)
 // warning C4522: multiple assignment operators specified
 #pragma warning(disable:4522)
 #endif
 // This is a container class for either an oop* or a narrowOop*.
 // Both are pushed onto a task queue and the consumer will test is_narrow()
 // to determine which should be processed.
 class StarTask {
   void*  _holder;        // either union oop* or narrowOop*
   enum { COMPRESSED_OOP_MASK = 1 };
  public:
   StarTask(narrowOop* p) {
     assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
     _holder = (void *)((uintptr_t)p | COMPRESSED_OOP_MASK);
   }
   StarTask(oop* p)       {
     assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
     _holder = (void*)p;
   }
   StarTask()             { _holder = NULL; }
   operator oop*()        { return (oop*)_holder; }
   operator narrowOop*()  {
     return (narrowOop*)((uintptr_t)_holder & ~COMPRESSED_OOP_MASK);
   }
   StarTask& operator=(const StarTask& t) {
     _holder = t._holder;
     return *this;
   }
   volatile StarTask& operator=(const volatile StarTask& t) volatile {
     _holder = t._holder;
     return *this;
   }
   bool is_narrow() const {
     return (((uintptr_t)_holder & COMPRESSED_OOP_MASK) != 0);
   }
 };
 class ObjArrayTask
 {
 public:
   ObjArrayTask(oop o = NULL, int idx = 0): _obj(o), _index(idx) { }
   ObjArrayTask(oop o, size_t idx): _obj(o), _index(int(idx)) {
     assert(idx <= size_t(max_jint), "too big");
   }
   ObjArrayTask(const ObjArrayTask& t): _obj(t._obj), _index(t._index) { }
   ObjArrayTask& operator =(const ObjArrayTask& t) {
     _obj = t._obj;
     _index = t._index;
     return *this;
   }
   volatile ObjArrayTask&
   operator =(const volatile ObjArrayTask& t) volatile {
     (void)const_cast<oop&>(_obj = t._obj);
     _index = t._index;
     return *this;
   }
   inline oop obj()   const { return _obj; }
   inline int index() const { return _index; }
   DEBUG_ONLY(bool is_valid() const); // Tasks to be pushed/popped must be valid.
 private:
   oop _obj;
   int _index;
 };
 #ifdef _MSC_VER
 #pragma warning(pop)
 #endif
 typedef OverflowTaskQueue<StarTask, mtClass>           OopStarTaskQueue;
 typedef GenericTaskQueueSet<OopStarTaskQueue, mtClass> OopStarTaskQueueSet;
 typedef OverflowTaskQueue<size_t, mtInternal>             RegionTaskQueue;
 typedef GenericTaskQueueSet<RegionTaskQueue, mtClass>     RegionTaskQueueSet;
 #endif // SHARE_VM_UTILITIES_TASKQUEUE_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/utilities/taskqueue.hpp@aefa2e84b424 (annotated)

src/share/vm/utilities/taskqueue.hpp