130 lines
3.0 KiB
C++
130 lines
3.0 KiB
C++
/*
|
|
Copyright (c) 2011, 2015, Oracle and/or its affiliates. All rights
|
|
reserved.
|
|
|
|
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; version 2 of
|
|
the License.
|
|
|
|
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., 51 Franklin St, Fifth Floor, Boston, MA
|
|
02110-1301 USA
|
|
*/
|
|
|
|
|
|
/* Lock-free SPSC queue. Safe for one consumer thread and one producer.
|
|
*
|
|
*/
|
|
|
|
#include <stdlib.h>
|
|
|
|
#include "ndbmemcache_global.h"
|
|
#include "atomics.h"
|
|
|
|
#define VPSZ sizeof(void *)
|
|
#define CACHE_PADDING (CACHE_LINE_SIZE - VPSZ)
|
|
|
|
|
|
template<typename T> class Queue {
|
|
private:
|
|
struct Node {
|
|
T * value;
|
|
Node * volatile next;
|
|
};
|
|
|
|
Node *head;
|
|
char padding1[CACHE_PADDING];
|
|
|
|
Node *sep;
|
|
char padding2[CACHE_PADDING];
|
|
|
|
Node *tail;
|
|
Node *nodelist;
|
|
char *nodepool;
|
|
atomic_int32_t is_active;
|
|
|
|
public: /* public instance variable */
|
|
|
|
public: /* public interface methods */
|
|
Queue(int maxnodes) {
|
|
/* Initialize the node allocation pool */
|
|
maxnodes += 1; // add one for a dummy node at the head.
|
|
assert(sizeof(Node) < CACHE_LINE_SIZE);
|
|
nodepool = (char *) calloc(maxnodes, CACHE_LINE_SIZE);
|
|
nodelist = 0;
|
|
for(int i = 0; i < maxnodes; i++) {
|
|
Node *n = (Node *) (nodepool + (i * CACHE_LINE_SIZE));
|
|
n->next = nodelist;
|
|
nodelist = n;
|
|
}
|
|
|
|
/* Initialize the queue */
|
|
head = node_alloc(0); // a dummy node
|
|
sep = head;
|
|
tail = sep; // an empty queue
|
|
|
|
is_active = 1;
|
|
};
|
|
|
|
~Queue() {
|
|
free(nodepool);
|
|
};
|
|
|
|
T * consume() {
|
|
T * val = 0;
|
|
Node *nxt = sep->next;
|
|
if(nxt) { /* queue is non-empty */
|
|
val = nxt->value; /* the value to be returned. */
|
|
nxt->value = 0; /* This node becomes the new (empty) dummy node... */
|
|
sep = nxt; /* at the head of the queue. */
|
|
}
|
|
return val;
|
|
};
|
|
|
|
void produce(T *t) {
|
|
/* First do deferred cleanup of the old nodes between head and sep */
|
|
while(head != sep) {
|
|
Node *tmp = head;
|
|
assert(tmp->value == 0);
|
|
head = tmp->next;
|
|
node_free(tmp);
|
|
}
|
|
/* Now add a node at the tail of the queue */
|
|
Node * n = node_alloc(t);
|
|
atomic_set_ptr((void * volatile *)& tail->next, n);
|
|
atomic_barrier();
|
|
tail = n;
|
|
};
|
|
|
|
void abort() {
|
|
atomic_cmp_swap_int(& is_active, 1, 0);
|
|
}
|
|
|
|
bool is_aborted() {
|
|
return (is_active == 0);
|
|
}
|
|
|
|
private: /* internal allocator */
|
|
Node *node_alloc(T *val) {
|
|
assert(nodelist);
|
|
Node *n = nodelist;
|
|
nodelist = n->next;
|
|
n->next = 0;
|
|
n->value = val;
|
|
return n;
|
|
};
|
|
|
|
void node_free(Node *n) {
|
|
n->next = nodelist;
|
|
nodelist = n;
|
|
};
|
|
};
|
|
|