hp.c

/*
 * Copyright (c) 2014 Mohamed L. Karaoui.
 * Copyright (c) 2014 Sorbonne Universités, UPMC Univ Paris 06.
 *
 * Parts copied from:
 *   T. E. Hart. "Making Lockless Synchronization Fast: Performance Implications of Memory Reclamation". 
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 */

#include "hp.h"
#include <stdlib.h>
#include "allocator_malloc.h"


zombie_list zlist[MAX_THREAD];

/* 
 * Comparison function for qsort.
 *
 * We just need any total order, so we'll use the arithmetic order 
 * of pointers on the machine.
 *
 * Output (see "man qsort"):
 *  < 0 : a < b
 *    0 : a == b
 *  > 0 : a > b
 */
int compare (const void *a, const void *b)
{
  return ( *(node_t **)a - *(node_t **)b );
}

void scan(int thread)
{
	/* Iteratation variables. */
	node_t *cur;
	int i;
	
	//printf("R: %d, number of blocked node %d\n", R, zlist[thread].number);
	nbblockeds=R;

	/* List of SMR callbacks. */
	node_t *tmplist;

	/* List of hazard pointers, and its size. */
	//FIXME improve write side avoid this alloc do it once...
	node_t **plist = malloc(sizeof(node_t *) * K * nbthreads);
	unsigned long psize;

	zombie_list *zl = &zlist[thread];
	/*
	 * Make sure that the most recent node to be deleted has been unlinked
	 * in all processors' views.
	 *
	 * Good:
	 *   A -> B -> C ---> A -> C ---> A -> C
	 *                    B -> C      B -> POISON
	 *
	 * Illegal:
	 *   A -> B -> C ---> A -> B      ---> A -> C
	 *                    B -> POISON      B -> POISON
	 */
	write_write_barrier();

	/* Stage 1: Scan HP list and insert non-null values in plist. */
	psize = 0;
	for (i = 0; i < H; i++) {
		if (HP[i].p != NULL)
			plist[psize++] = HP[i].p;
	}
	
	/* Stage 2: Sort the plist. */
	qsort(plist, psize, sizeof(node_t *), compare);

	/* Stage 3: Free non-harzardous nodes. */
	tmplist = zl->p;
	zl->p = NULL;
	zl->number = 0;

	while (tmplist != NULL) {
		/* Pop cur off top of tmplist. */
		cur = tmplist;
		tmplist = tmplist->mr_next;

		if (bsearch(&cur, plist, psize, sizeof(node_t *), compare)) {
			cur->mr_next = zl->p;
			zl->p = cur;
			zl->number++;
		} else {
			free_node(cur);
		}
	}
}

void free_node_later(int thread, node_t * node)
{
    zombie_list *zl = &zlist[thread];
    node->mr_next = zl->p;
    zl->p = node;
    if(++zl->number > R)
        scan(thread);
}

node_t* init_new_node()
{
	return new_node();
}