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// -*- C++ -*-
/*
The Hoard Multiprocessor Memory Allocator
www.hoard.org
Author: Emery Berger, http://www.emeryberger.com
Copyright (c) 1998-2020 Emery Berger
See the LICENSE file at the top-level directory of this
distribution and at http://github.com/emeryberger/Hoard.
*/
#ifndef HOARD_REDIRECTFREE_H
#define HOARD_REDIRECTFREE_H
#include "heaplayers.h"
namespace Hoard {
/**
* @class RedirectFree
* @brief Routes free calls to the Superblock's owner heap.
* @note We also lock the heap on calls to malloc.
*/
template <class Heap,
typename SuperblockType_>
class RedirectFree {
public:
enum { Alignment = Heap::Alignment };
typedef SuperblockType_ SuperblockType;
RedirectFree()
{
}
inline void * malloc (size_t sz) {
void * ptr = _theHeap.malloc (sz);
assert (getSize(ptr) >= sz);
assert ((size_t) ptr % Alignment == 0);
return ptr;
}
size_t getSize (void * ptr) {
return Heap::getSize (ptr);
}
SuperblockType * getSuperblock (void * ptr) {
return Heap::getSuperblock (ptr);
}
/// Free the given object, obeying the required locking protocol.
static inline void free (void * ptr) {
// Get the superblock header.
SuperblockType * s = reinterpret_cast<SuperblockType *>(Heap::getSuperblock (ptr));
assert (s->isValidSuperblock());
// Find out who the owner is.
typedef BaseHoardManager<SuperblockType> * baseHeapType;
baseHeapType owner;
s->lock();
// By acquiring the lock on the superblock (above),
// we prevent it from moving up to a higher heap.
// This eventually pins it down in one heap,
// so this loop is guaranteed to terminate.
// (It should generally take no more than two iterations.)
for (;;) {
owner = reinterpret_cast<baseHeapType>(s->getOwner());
assert (owner != nullptr);
assert (owner->isValid());
// Lock the owner. If ownership changed between these two lines,
// we'll detect it and try again.
owner->lock();
if (owner == reinterpret_cast<baseHeapType>(s->getOwner())) {
owner->free (ptr);
owner->unlock();
s->unlock();
return;
}
owner->unlock();
// Sleep a little.
HL::Fred::yield();
}
}
private:
Heap _theHeap;
};
}
#endif