121 строка
4.3 KiB
C
121 строка
4.3 KiB
C
/*
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* Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
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* University Research and Technology
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* Corporation. All rights reserved.
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* Copyright (c) 2004-2007 The University of Tennessee and The University
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* of Tennessee Research Foundation. All rights
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* reserved.
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* Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
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* University of Stuttgart. All rights reserved.
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* Copyright (c) 2004-2005 The Regents of the University of California.
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* All rights reserved.
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* Copyright (c) 2007 Voltaire All rights reserved.
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* $COPYRIGHT$
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*
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* Additional copyrights may follow
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*
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* $HEADER$
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*/
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#ifndef OPAL_ATOMIC_LIFO_H_HAS_BEEN_INCLUDED
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#define OPAL_ATOMIC_LIFO_H_HAS_BEEN_INCLUDED
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#include "opal_config.h"
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#include "opal/class/opal_list.h"
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#if OMPI_HAVE_THREAD_SUPPORT
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#include "opal/sys/atomic.h"
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#endif /* OMPI_HAVE_THREAD_SUPPORT */
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#if defined(c_plusplus) || defined(__cplusplus)
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extern "C" {
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#endif
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/* Atomic Last In First Out lists. If we are in a multi-threaded environment then the
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* atomicity is insured via the compare-and-swap operation, if not we simply do a read
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* and/or a write.
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*
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* There is a trick. The ghost element at the end of the list. This ghost element has
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* the next pointer pointing to itself, therefore we cannot go past the end of the list.
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* With this approach we will never have a NULL element in the list, so we never have
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* to test for the NULL.
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*/
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struct opal_atomic_lifo_t
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{
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opal_object_t super;
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opal_list_item_t* opal_lifo_head;
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opal_list_item_t opal_lifo_ghost;
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};
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typedef struct opal_atomic_lifo_t opal_atomic_lifo_t;
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OPAL_DECLSPEC OBJ_CLASS_DECLARATION(opal_atomic_lifo_t);
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/* The ghost pointer will never change. The head will change via an atomic
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* compare-and-swap. On most architectures the reading of a pointer is an
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* atomic operation so we don't have to protect it.
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*/
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static inline bool opal_atomic_lifo_is_empty( opal_atomic_lifo_t* lifo )
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{
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return (lifo->opal_lifo_head == &(lifo->opal_lifo_ghost) ? true : false);
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}
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/* Add one element to the LIFO. We will return the last head of the list
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* to allow the upper level to detect if this element is the first one in the
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* list (if the list was empty before this operation).
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*/
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static inline opal_list_item_t* opal_atomic_lifo_push( opal_atomic_lifo_t* lifo,
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opal_list_item_t* item )
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{
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#if OMPI_HAVE_THREAD_SUPPORT
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do {
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item->opal_list_next = lifo->opal_lifo_head;
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if( opal_atomic_cmpset_ptr( &(lifo->opal_lifo_head),
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(void*)item->opal_list_next,
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item ) ) {
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opal_atomic_cmpset_32((volatile int32_t*)&item->item_free, 1, 0);
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return (opal_list_item_t*)item->opal_list_next;
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}
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/* DO some kind of pause to release the bus */
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} while( 1 );
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#else
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item->opal_list_next = lifo->opal_lifo_head;
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lifo->opal_lifo_head = item;
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return (opal_list_item_t*)item->opal_list_next;
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#endif /* OMPI_HAVE_THREAD_SUPPORT */
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}
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/* Retrieve one element from the LIFO. If we reach the ghost element then the LIFO
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* is empty so we return NULL.
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*/
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static inline opal_list_item_t* opal_atomic_lifo_pop( opal_atomic_lifo_t* lifo )
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{
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opal_list_item_t* item;
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#if OMPI_HAVE_THREAD_SUPPORT
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while((item = lifo->opal_lifo_head) != &(lifo->opal_lifo_ghost))
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{
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if(!opal_atomic_cmpset_32((volatile int32_t*)&item->item_free, 0, 1))
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continue;
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if( opal_atomic_cmpset_ptr( &(lifo->opal_lifo_head),
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item,
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(void*)item->opal_list_next ) )
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break;
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opal_atomic_cmpset_32((volatile int32_t*)&item->item_free, 1, 0);
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/* Do some kind of pause to release the bus */
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}
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#else
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item = lifo->opal_lifo_head;
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lifo->opal_lifo_head = (opal_list_item_t*)item->opal_list_next;
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#endif /* OMPI_HAVE_THREAD_SUPPORT */
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if( item == &(lifo->opal_lifo_ghost) ) return NULL;
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item->opal_list_next = NULL;
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return item;
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}
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#if defined(c_plusplus) || defined(__cplusplus)
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}
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#endif
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#endif /* OPAL_ATOMIC_LIFO_H_HAS_BEEN_INCLUDED */
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